Light source device and inspection device

Abstract

The present invention provides a light source device and inspection device that can obtain output light with a high pulse repetition frequency and low instantaneous peak output with a small number of components, while maintaining a time-averaged output level in relation to the laser light before instantaneous peak output adjustment. [Solution] A light source device according to one embodiment of the present invention comprises a light source capable of outputting pulsed laser light and a composite prism in which a plurality of prisms and one or more partial reflective films are integrated. The composite prism divides the incident pulsed laser light in time within the composite prism by total internal reflection in at least one of the plurality of prisms and partial internal reflection and partial transmission in one or more partial reflective films, thereby generating and outputting time-resolved pulsed laser light in which the pulsed light contained in the pulsed laser light is divided in time.

Description

[Technical Field]

[0001] The present invention relates to a light source device and an inspection device. [Background Art]

[0002] As a laser light source used for inspection and measurement of semiconductors and the like, a continuous wave (CW) light source is generally most suitable in many cases. Since a CW light source always maintains a constant output level, continuous acquisition of images or data is enabled. In addition, since the output level is low, damage to optical elements and inspection objects is also small. However, CW light sources having sufficient time-averaged output in specific wavelength ranges such as the ultraviolet region have not been put into practical use due to technical difficulties.

[0003] Pulsed laser light sources are widely used as alternative light sources to CW light sources. The instantaneous peak output of a pulsed laser light source is calculated from the time-averaged output, the pulse repetition frequency, and the pulse width. The instantaneous peak output of a pulsed laser light source is much higher than the time-averaged output level of a CW light source. For example, when the time-averaged output is 4 [W], the pulse repetition frequency is 100 [MHz], and the pulse width is 10 [ps], the instantaneous peak output of the pulsed laser light reaches as high as 4 [kW]. Therefore, when a pulsed laser light source is used as the light source of an inspection apparatus, damage to optical elements and the inspection object becomes a problem.

[0004] It is known that increasing the pulse repetition frequency or extending the pulse width while keeping the time-averaged output level constant reduces the instantaneous peak output. Therefore, in a pulsed laser light source, it is conceivable to increase the pulse repetition frequency or extend the pulse width in order to reduce the instantaneous peak output (see, for example, Non-Patent Documents 1 and 2). [Prior Art Literature] [Patent Literature]

[0005] [Patent Literature 1] Japanese Patent No. 6545750 [Non-Patent Literature]

[0006] [Non-Patent Document 1] S. Chaitanya Kumar, J. Canals Casals, Junxiong Wei, and M. Ebrahim-Zadeh1, High-power, high-repetition-rate performance characteristics of β-BaB2O4 for single-pass picosecond ultraviolet generation at 266 nm, Optics Express, 23 (21), pp.28091-28103(2015) https: / / doi.org / 10.1364 / OE.23.028091 [Non-Patent Document 2] KENTARO MIYATA, MIZUKI MOHARA, KEI SHIMURA, AKIHIRO TANABASHI, LOUIS DESBIENS, VINCENT ROY, YVES TAILLON, SHINICHI NAKAYAMA, AND SATOSHI WADA, Programmable deep-UV laser platform for inspection and metrology, Optics Letters, 44(22), pp5818-5821 (2019) https: / / doi.org / 10.1364 / OL.44.005618 [Overview of the initiative] [Problems that the invention aims to solve]

[0007] In the inventions described in Non-Patent Documents 1 and 2, near-infrared pulsed laser light is irradiated onto a nonlinear optical crystal as fundamental light, and converted into ultraviolet pulsed laser light in the nonlinear optical crystal. The ultraviolet pulsed laser light obtained from the nonlinear optical crystal can be used as light to irradiate the object to be inspected. In the inventions described in Non-Patent Documents 1 and 2, in order to increase the pulse repetition frequency or pulse width of the ultraviolet pulsed laser light, it is necessary to increase the pulse repetition frequency or pulse width of the fundamental light.

[0008] However, if such adjustments are made to the fundamental light, the instantaneous peak output of the fundamental light itself decreases, and the time-averaged output level of the ultraviolet pulsed laser light, which is the output of the nonlinear optical crystal, also decreases. From this, it can be seen that increasing the pulse repetition frequency or lengthening the pulse width in order to lower the instantaneous peak output is not a good idea.

[0009] As a method for reducing instantaneous peak output while maintaining a constant time-averaged output level, for example, Patent Document 1 proposes a pulse multiplier (pulse division device) using a polarizing beam splitter and a waveplate. However, when a large number of optical elements are arranged on the optical path in this way, precise positional adjustment of each optical element is required, and this also leads to the problem of increasing the size of the device. Therefore, it is desirable to provide a light source device and inspection device that can obtain output light with a high pulse repetition frequency and low instantaneous peak output with a small number of components, while maintaining the time-averaged output level in relation to the laser light before instantaneous peak output adjustment. [Means for solving the problem]

[0010] A light source device according to one embodiment of the present invention comprises a light source capable of outputting pulsed laser light and a composite prism in which a plurality of prisms and one or more partial reflective films are integrated. The composite prism temporally divides the incident pulsed laser light within the composite prism by total internal reflection in at least one of the plurality of prisms and partial internal reflection and partial transmission in one or more partial reflective films, thereby generating and outputting time-resolved pulsed laser light in which the pulsed light contained in the pulsed laser light is temporally divided.

[0011] An inspection apparatus according to one embodiment of the present invention comprises a light source device capable of outputting inspection light to an object to be inspected, and a processing device capable of inspecting the object based on the reflected light from the object or the transmitted light from the object. The light source device included in the inspection apparatus has the same configuration as the above-described light source device. [Effects of the Invention]

[0012] In a light source device and inspection device according to one embodiment of the present invention, the incident pulsed laser light is temporally divided within the composite prism by total internal reflection in multiple prisms and partial internal reflection and partial transmission in one or more partial reflective films. As a result, time-division pulsed laser light with a higher pulse repetition frequency and lower instantaneous peak output is obtained compared to pulsed laser light incident on the composite prism, without causing a decrease in the time-averaged output level. Furthermore, the composite prism is a single optical element in which multiple prisms and one or more partial reflective films are integrated. This eliminates the need for precise positioning adjustments required when arranging a large number of optical elements on the optical path. Therefore, in relation to the pulsed laser light incident on the composite prism, time-division pulsed laser light with a high pulse repetition frequency and low instantaneous peak output can be obtained with a small number of parts while maintaining the time-averaged output level. [Brief explanation of the drawing]

[0013] [Figure 1]FIG. 1 is a diagram illustrating an example of a functional block of an inspection apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a modified example of the functional block of the inspection apparatus of FIG. 1. [Figure 3] FIG. 3 is a diagram illustrating an example of a waveform of pulsed laser light emitted from the pulsed laser light source of FIG. 1. [Figure 4] FIG. 4 is a diagram illustrating a configuration example of the time-division apparatus in FIGS. 1 and 2. [Figure 5] FIG. 5 is a diagram for explaining an optical action in the time-division apparatus of FIG. 4. [Figure 6] FIG. 6 is a diagram illustrating an example of a waveform of time-division pulsed laser light that is output light of the time-division apparatus of FIG. 4. [Figure 7] FIG. 7 is a diagram illustrating a modified example of the configuration of the time-division apparatus of FIG. 4. [Figure 8] FIG. 8 is a diagram for explaining an optical action in the time-division apparatus of FIG. 7. [Figure 9] FIG. 9 is a diagram illustrating an example of a waveform of time-division pulsed laser light that is output light of the time-division apparatus of FIG. 7. [Figure 10] FIG. 10 is a diagram illustrating a modified example of the configuration of the time-division apparatus of FIG. 4. [Figure 11] FIG. 11 is a diagram for explaining an optical action in the time-division apparatus of FIG. 10. [Figure 12] FIG. 12 is a diagram illustrating a modified example of the configuration of the time-division apparatus of FIG. 4. [Figure 13] FIG. 13 is a diagram for explaining an optical action in the time-division apparatus of FIG. 12. [Figure 14] FIG. 14 is a diagram illustrating a modified example of the configuration of the time-division apparatus of FIG. 4. [Figure 15] FIG. 15 is a diagram for explaining an optical action in the time-division apparatus of FIG. 14. [Figure 16] FIG. 16 is a diagram illustrating a modified example of the configuration of the time-division apparatus of FIG. 4. [Figure 17] FIG. 17 is a diagram for explaining an optical action in the time-division apparatus of FIG. 16. [Figure 18] Figure 18 shows a modified example of the configuration of the time-division multiplexer shown in Figure 7. [Figure 19] Figure 19 shows a modified example of the configuration of the time-division multiplexer shown in Figure 10. [Figure 20] Figure 20 shows a modified example of the configuration of the time-division multiplexer shown in Figure 12. [Figure 21] Figure 21 shows a modified example of the configuration of the time-division multiplexer shown in Figure 16. [Modes for carrying out the invention]

[0014] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. The following description is one specific example of the present invention, and the present invention is not limited to the following embodiments. Furthermore, the present invention is not limited to the arrangement, dimensions, dimensional ratios, etc., of each component shown in each figure.

[0015] <1. Embodiment> [composition] Figures 1 and 2 show an example of the functional block of an inspection apparatus 100 according to one embodiment of the present invention. The inspection apparatus 100 is capable of inspecting whether or not there are defects in a target TG by irradiating the target TG with pulsed laser light and processing the transmitted light L3 or reflected light L4 from the target TG. The target TG is an element with a stacked structure inside, or an element with a fine pattern inside or on its outermost surface. The target TG is, for example, a wafer used in the semiconductor manufacturing process or a substrate on which a photomask used for exposure is formed. The inspection apparatus 100 includes, for example, a pulsed laser light source 110, a time-division multiplexer 120, and a processing unit 130, as shown in Figure 1.

[0016] The inspection device 100 corresponds to a specific example of the "inspection device" in one embodiment of the present invention. The pulsed laser light source 110 corresponds to a specific example of the "light source" in one embodiment of the present invention. The time-division device 120 corresponds to a specific example of the "composite prism" in one embodiment of the present invention. The device composed of the pulsed laser light source 110 and the time-division device 120 corresponds to a specific example of the "light source device" in one embodiment of the present invention.

[0017] The pulsed laser light source 110 is capable of outputting pulsed laser light L1, which is linearly polarized light. The pulsed laser light source 110 is composed of, for example, a wavelength conversion type light source that combines a solid laser and a nonlinear optical crystal, and an optical lens group that can parallelize the laser light output from the wavelength conversion type light source. Parallelized pulsed laser light L1 is output from the pulsed laser light source 110. The pulsed laser light L1 is incident as p-polarized light on an interface such as the main prism 121, which will be described later.

[0018] Figure 3 shows an example waveform of pulsed laser light L1. The pulse repetition frequency of pulsed laser light L1 is, for example, 100 MHz. The pulse repetition frequency is expressed as 1 / (number of pulses generated per second). The wavelength range of pulsed laser light L1 is, for example, the ultraviolet region. Pulsed laser light L1 has a peak wavelength in the ultraviolet region, for example. Pulsed laser light L1 has a peak wavelength at 266 nm, 213 nm, or 193 nm, for example.

[0019] The processing unit 130 is capable of inspecting whether or not there are defects in the TG under inspection by processing transmitted light L3 or reflected light L4. The processing unit 130 is configured to include, for example, a photodetector that receives transmitted light L3 or reflected light L4, and one or more processors capable of inspecting whether or not there are defects in the TG under inspection based on the output signal from the photodetector.

[0020] Figure 4 shows an example configuration of the time-division device 120. Figure 5 explains the optical operation in the time-division device 120. Figure 6 shows an example waveform of the time-division pulsed laser light L2, which is the output light of the time-division device 120.

[0021] The time-division device 120 is a composite prism in which multiple prisms and one or more partial reflective films are integrated. The composite prism divides the incident pulsed laser light L1 in time within the composite prism by total internal reflection in the multiple prisms, as well as by partial reflection and partial transmission in one or more partial reflective films, thereby generating and outputting time-division pulsed laser light L2, which is the pulsed laser light L1 divided in time. Here, the time-division pulsed laser light L2 is a laser light that includes a pulse train in which multiple pulses obtained by time-division of the pulsed laser light L1 do not overlap with each other in time.

[0022] The composite prism includes, for example, a main prism 121 and a secondary prism 122 as multiple prisms, as shown in Figure 4. The secondary prism 122 is fixed to the main prism 121. The composite prism further includes, for example, one or more partial reflective films, as shown in Figure 4, a partial reflective film 123a. The composite prism further includes, for example, anti-reflective films 123b and 123c, as shown in Figure 4. The main prism 121 corresponds to one specific example of the "first prism" or "first rectangular prism prism" in one embodiment of the present invention. The secondary prism 122 corresponds to one specific example of the "second prism" in one embodiment of the present invention. The partial reflective film 123a corresponds to one specific example of the "one or more partial reflective films" or "first partial reflective film" in one embodiment of the present invention.

[0023] The partial reflective film 123a is provided between the main prism 121 and the sub-prism 122. The partial reflective film 123a is in contact with the end face of the main prism 121 (end face S1 described later) and the end face of the sub-prism 122 (end face S7 described later). The partial reflective film 123a is a beam splitter capable of splitting the pulsed laser light L1 into transmitted light and reflected light. The partial reflective film 123a has a film structure in which the transmittance is greater than the reflectance when the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°.

[0024] The partial reflective film 123a is capable of splitting pulsed laser light L1 into transmitted light L11t and reflected light L11r when pulsed laser light L1 is incident as p-polarized light from the sub-prism 122 side at an incident angle of 45°. The partial reflective film 123a is capable of splitting transmitted light L11t into transmitted light L12t and reflected light L12r when transmitted light L11t, which has returned due to total internal reflection at the main prism 121, is incident as p-polarized light from the main prism 121 side at an incident angle of 45°. Transmitted light L12t is emitted in a direction coaxial with reflected light L11r. Reflected light L12r is emitted in a direction coaxial with transmitted light L11t. The partial reflective film 123a is capable of splitting the reflected light L12r, which has returned due to total internal reflection at the main prism 121, into transmitted light L13t and reflected light L13r when it is incident from the main prism 121 side as p-polarized light at an incident angle of 45°. The transmitted light L13t is emitted in a direction coaxial with the reflected light L11r. The reflected light L13r is emitted in a direction coaxial with the transmitted light L11t.

[0025] The anti-reflective coating 123b is in contact with the light incident surface (end face S5, described later) of the main prism 121. The anti-reflective coating 123b has a film structure such that when pulsed laser light L1 is incident perpendicularly to the end face S5, the reflectance at the end face S5 is lower than the reflectance when the anti-reflective coating 123b is not provided on the end face S5. The anti-reflective coating 123c is in contact with the light output surface (end face S6, described later) of the main prism 121. The anti-reflective coating 123c has a film structure such that when reflected light L11r, transmitted light L12t, and transmitted light L13t are incident perpendicularly to the end face S6, the reflectance at the end face S6 is lower than the reflectance when the anti-reflective coating 123c is not provided on the end face S6.

[0026] The main prism 121 is a single rectangular prism. In this specification, "single" means that there is no bonding interface inside. A rectangular prism is a concept that includes a hexahedron prism with a square base, a cuboid prism with a rectangular base, and a cube prism with a square base. Hereafter, the main prism 121 will be described as a cuboid prism or a cube prism. The main prism 121 has an end face S1 to which the sub-prism 122 is fixed, an end face S2 parallel to end face S1, and end faces S3 and S4 perpendicular to end face S1. The end faces S1, S2, S3, and S4 are planar. The end faces S2, S3, and S4 are not coated with optical films such as total reflection films. Therefore, the end faces S2, S3, and S4 are uncoated surfaces.

[0027] The end faces S2, S3, and S4 are capable of totally internalizing transmitted light L11t and reflected light L12r and L13r when they are incident as p-polarized light at an incident angle of 45° within the main prism 121. The composite prism can temporally divide the incident pulsed laser light L1 within the composite prism through partial reflection and partial transmission at the partial reflective film 123a and total internal reflection at the end faces S2, S3, and S4. As a result, the composite prism can generate and output time-resolved pulsed laser light L2.

[0028] End face S1 corresponds to a specific example of the "first end face" of one embodiment of the present invention. End face S2 corresponds to a specific example of the "second end face" of one embodiment of the present invention. End face S3 corresponds to a specific example of the "third end face" of one embodiment of the present invention. End face S4 corresponds to a specific example of the "fourth end face" of one embodiment of the present invention.

[0029] The sub-prism 122 is a single right-angle prism. The sub-prism 122 has mutually orthogonal end faces S5 and S6, and an end face S7 connected to end faces S5 and S6. The angle between end face S5 and end face S7 is 45°. The angle between end face S6 and end face S7 is 45°. End face S5 is the incident surface for pulsed laser light L1. End face S6 is the exit surface for time-resolved pulsed laser light L2. End face S7 is the surface fixed to end face S1 of the main prism 121 via a partial reflective film 123a.

[0030] End face S5 corresponds to a specific example of the "fifth end face" of one embodiment of the present invention. End face S6 corresponds to a specific example of the "sixth end face" of one embodiment of the present invention. End face S7 corresponds to a specific example of the "seventh end face" of one embodiment of the present invention.

[0031] The main prism 121 and the sub-prism 122 are both made of a common material. The main prism 121 and the sub-prism 122 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prism 122 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prism 122 may also be made of, for example, quartz or lithium tetraborate (LB4). The joining of the main prism 121 and the sub-prism 122 is performed, for example, by optical joining (optical contact). The joining of the main prism 121 and the sub-prism 122 may also be performed, for example, by adhesive joining or diffusion bonding.

[0032] [Effect] Next, we will explain the effect of the time-resolved device 120 on the pulsed laser light L1.

[0033] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prism 122 are made of calcium fluoride. In this case, the refractive index of the main prism 121 and the sub-prism 122 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. The total reflection angles of the end faces S5 and S6 of the sub-prism 122 are 43.2°. The optical path length of the optical path through which the transmitted light L11t, reflected light L12r, and reflected light L13r propagate within the main prism 121 is 80 mm. The time delay between pulses propagating within the main prism 121 is approximately 390.2 ps.

[0034] When transmitted light L11t, reflected light L12r, and reflected light L13r are incident as p-polarized light at an incident angle of 45° on end faces S2, S3, and S4 within the main prism 121, the transmitted light L11t, reflected light L12r, and reflected light L13r are totally internally reflected at end faces S2, S3, and S4. When pulsed laser light L1 is incident at an incident angle of 0° on end face S5 of the sub-prism 122, the pulsed laser light L1 is transmitted through end face S5 with almost no reflection. When reflected light L11r, transmitted light L12t, or transmitted light L13t is incident at an incident angle of 0° on end face S6 of the sub-prism 122, the reflected light L11r, transmitted light L12t, or transmitted light L13t are transmitted through end face S6 with almost no reflection and output to the outside of the sub-prism 122.

[0035] Let R be the reflectance of the partial reflective film 123a to pulsed laser light L1. The reflectance R is (1 - (R / 100)). 2 Let's assume the value that satisfies =R / 100 is 38.2%. The transmittance of the partial reflective film 123a to pulsed laser light L1 is expressed as (100-R) and is 61.8%. In the partial reflective film 123a, the transmittance (100-R) is greater than the reflectance R.

[0036] The reflected light L11r is the light obtained when the pulsed laser light L1 is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1. The transmitted light L12t is the light obtained when the transmitted light L11t passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L12t is 38.2% (= 61.8% × 61.8%) of the instantaneous peak output of the pulsed laser light L1.

[0037] The transmitted light L13t is the light obtained when the reflected light L12r passes through the partial reflective film 123a. The reflected light L12r is the light obtained when the transmitted light L11t is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L13t is 14.6% (=61.8% × 38.2% × 61.8%) of the instantaneous peak output of the pulsed laser light L1. The reflectance of the partial reflective film 123a represents the reflectance for linearly polarized light (p-polarized light). The transmittance of the partial reflective film 123a represents the transmittance for linearly polarized light (p-polarized light).

[0038] Next, we will explain the process by which pulsed laser light L1 is incident on a composite prism and time-resolved pulsed laser light L2 is output from the composite prism. Assume that the wavelength of pulsed laser light L1 is 266 nm. Assume that the main prism 121 and sub-prism 122 are constructed containing calcium fluoride. Assume that the reflectance R of the partial reflective film 123a is 38.2%, and the transmittance (100-R) of the partial reflective film 123a is 61.8%.

[0039] First, pulsed laser light L1 is incident on the sub-prism 122 at an incident angle of 0°. The pulsed laser light L1 incident on the sub-prism 122 is then incident on the partial reflective film 123a at an incident angle of 45° as p-polarized light, and is split into transmitted light L11t and reflected light L11r. The instantaneous peak output of the transmitted light L11t is 61.8% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1.

[0040] The reflected light L11r is output to the outside from the end face S6 of the sub-prism 122. The transmitted light L11t propagates inside the main prism 121 and is incident on the end faces S2, S3, and S4 of the main prism 121 as p-polarized light at an incident angle of 45°. The transmitted light L11t undergoes total internal reflection at the end faces S2, S3, and S4, and as a result returns to the end face S1 of the main prism 121 (i.e., the partial reflective film 123a). The transmitted light L11t reaches the partial reflective film 123a at a time delayed by the time required for the transmitted light L11t to undergo total internal reflection at the main prism 121 and return to the partial reflective film 123a compared to the time when the reflected light L11r was generated.

[0041] The transmitted light L11t that reaches the partial reflective film 123a is incident on the partial reflective film 123a as p-polarized light at an incident angle of 45°, and is split into transmitted light L12t and reflected light L12r. The instantaneous peak output of the transmitted light L12t is 38.2% (=61.8% × 61.8%) of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the reflected light L12r is 23.6% (=61.8% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0042] The transmitted light L12t is output to the outside from the end face S6 of the sub-prism 122. The reflected light L12r propagates inside the main prism 121 and is incident on the end faces S2, S3, and S4 of the main prism 121 as p-polarized light at an incident angle of 45°. The reflected light L12r undergoes total internal reflection at the end faces S2, S3, and S4, and as a result returns to the end face S1 of the main prism 121 (i.e., the partial reflective film 123a). The reflected light L12r reaches the partial reflective film 123a at a time delayed by the time it takes for the reflected light L12r to undergo total internal reflection at the main prism 121 and return to the partial reflective film 123a compared to the time when the transmitted light L12t was generated.

[0043] The reflected light L12r that reaches the partial reflective film 123a is incident on the partial reflective film 123a as p-polarized light at an incident angle of 45°, and is split into transmitted light L13t and reflected light L13r. The instantaneous peak output of the transmitted light L13t is 14.6% (=61.8% × 38.2% × 61.8%) of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the reflected light L13r is 9.0% (=61.8% × 38.2% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0044] From the end face S6 of the sub-prism 122, a pulse train including reflected light L11r, transmitted light L12t, and transmitted light L13t is output, for example, as shown in Figure 6. Here, transmitted light L12t is a pulse light that is delayed by the time required for transmitted light L12t to be totally reflected by the main prism 121 and return to the partial reflective film 123a compared to the time when reflected light L11r was generated. Transmitted light L13t is a pulse light that is delayed by the time required for transmitted light L13t to be totally reflected by the main prism 121 and return to the partial reflective film 123a compared to the time when transmitted light L12t was generated. The time required for transmitted light L12t or transmitted light L13t to be totally reflected by the main prism 121 and return to the partial reflective film 123a is at least longer than the pulse width of the pulsed laser light L1. The instantaneous peak output of transmitted light L12t is 38.2% (=61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of transmitted light L13t is 14.6% (=61.8% × 38.2% × 61.8%) of the instantaneous peak output of pulsed laser light L1.

[0045] The light containing the pulse train output from the end face S6 of the sub-prism 122 becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only divided in time within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 61.8% lower than the instantaneous peak output of the pulsed laser beam L1.

[0046] [effect] Next, we will explain the effects of the time-division multiplexer 120.

[0047] In this embodiment, the incident pulsed laser beam L1 is temporally divided within the composite prism by total internal reflection in multiple prisms and partial reflection and partial transmission in one or more partial reflective films. This results in a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. Furthermore, the composite prism is a single optical element in which multiple prisms and one or more partial reflective films are integrated. This eliminates the need for precise positional adjustments required when arranging numerous optical elements in the optical path. As a result, a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output can be obtained with a small number of components while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0048] In this embodiment, the multiple prisms include a main prism 121 and a sub-prism 122. A partial reflective film 123a is provided between the main prism 121 and the sub-prism 122, and the pulsed laser beam L1 is split into transmitted and reflected light by the partial reflective film 123a. As a result, a time-division pulsed laser beam L2 is obtained that has a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. Consequently, a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output can be obtained while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0049] In this embodiment, the main prism 121 is a rectangular prism having end faces S1, S2, S3, and S4. In the composite prism, time-division pulsed laser light L2 is generated by partial reflection and partial transmission at the partial reflective film 123a and total reflection at the end faces S2, S3, and S4. As a result, time-division pulsed laser light L2 is obtained with a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser light L1 incident on the composite prism, without causing a decrease in the time-averaged output level. Consequently, in relation to the pulsed laser light L1 incident on the composite prism, time-division pulsed laser light L2 with a higher pulse repetition frequency and lower instantaneous peak output can be obtained while maintaining the time-averaged output level.

[0050] In this embodiment, the sub-prism 122 is a right-angle prism. The partial reflective film 123a is in contact with the end face S1 of the main prism 121 and the end face S7 of the sub-prism 122. In the sub-prism 122, the end face S5 is the incident surface for the pulsed laser light L1, and the end face S6 is the output surface for the time-division pulsed laser light L2. This allows a portion of the pulsed laser light L1 to be efficiently transmitted into the main prism 121. Furthermore, the light transmitted into the main prism 121 (transmitted light L11t) can be incident on the end faces S2, S3, and S4 of the main prism 121 under total internal reflection conditions. In addition, of the transmitted light L11t, the light that has passed through the partial reflective film 123a (transmitted light L12t) is output from the end face S6 of the sub-prism 122 a predetermined time delay compared to when the reflected light L11r is output from the end face S6 of the sub-prism 122. As a result, in relation to the pulsed laser light L1 incident on the composite prism, it is possible to obtain a time-resolved pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level.

[0051] In this embodiment, the pulsed laser light L1 has a peak wavelength in the ultraviolet region. Therefore, the time-resolved pulsed laser light L2 also has a peak wavelength in the ultraviolet region. As a result, the time-resolved pulsed laser light L2 can be suitably used as inspection light for inspecting the target TG.

[0052] In this embodiment, when the pulsed laser light L1 is unpolarized light, the partial reflective film 123a has a film structure in which the transmittance is greater than the reflectance when the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°. This allows a portion of the pulsed laser light L1 to be efficiently transmitted into the main prism 121.

[0053] In this embodiment, the partial reflective film 123a has a film structure in which the transmittance is greater than the reflectance when the pulsed laser light L1, which is linearly polarized light, is incident as p-polarized light at an incident angle of 45°. This allows a portion of the pulsed laser light L1 to be efficiently transmitted into the main prism 121.

[0054] <2. Variant> Next, a modified example of the time-division device 120 according to the above embodiment will be described.

[0055] <Variation A> Figure 7 shows a modified configuration of the time-division device 120. Figure 8 is a diagram illustrating the optical operation of the time-division device 120 in Figure 7. In the above embodiment, the time-division device 120 may have a sub-prism 124 instead of the sub-prism 122, for example, as shown in Figure 7. The sub-prism 124 corresponds to one specific example of the "multiple prisms" or "second prism" in one embodiment of the present invention.

[0056] The sub-prism 124 is a single isosceles trapezoidal prism. The sub-prism 124 has an end face S8 corresponding to the top base of the trapezoid, an end face S9 corresponding to the bottom base of the trapezoid, and end faces S10 and S11 corresponding to the legs of the trapezoid. The angle between end face S8 and end face S10 is 135°. The angle between end face S8 and end face S11 is 135°. The angle between end face S9 and end face S10 is 45°. The angle between end face S9 and end face S11 is 45°. End face S10 is a plane perpendicular to end face S11. End face S10 is the incident surface of pulsed laser light L1. End face S11 is the exit surface of time-resolved pulsed laser light L2.

[0057] End face S8 corresponds to a specific example of the "eighth end face" of one embodiment of the present invention. End face S9 corresponds to a specific example of the "ninth end face" of one embodiment of the present invention. End face S10 corresponds to a specific example of the "tenth end face" of one embodiment of the present invention. End face S11 corresponds to a specific example of the "eleventh end face" of one embodiment of the present invention.

[0058] In this modified example, the composite prism further includes sub-prisms 125 and 126, as shown in Figure 7. Sub-prism 125 is fixed to the end face S2 of the main prism 121, excluding the area where the transmitted light L11t described later is totally reflected. Sub-prism 126 is fixed to the end face S3 of the main prism 121, excluding the area where the transmitted light L11t described later is totally reflected. Sub-prism 125 corresponds to a specific example of the "third prism" in one embodiment of the present invention. Sub-prism 126 corresponds to a specific example of the "fourth prism" in one embodiment of the present invention.

[0059] Sub-prisms 125 and 126 are single rectangular prism-shaped prisms that provide a time delay. By adjusting the size of sub-prisms 125 and 126, it is possible to adjust the delay time of the transmitted light L112t, reflected light L212r, and transmitted light L122t relative to the reflected light L111r. This delay time is at least longer than the pulse width of the pulsed laser light L1. Figure 9 shows an example of the waveform of the time-resolved pulsed laser light L2 when the delay time of the transmitted light L112t, reflected light L212r, and transmitted light L122t relative to the reflected light L111r is longer than the pulse width of the pulsed laser light L1.

[0060] A rectangular prism is a concept that includes a hexahedron prism with a square face in contact with the main prism 121, a rectangular prism with a rectangular face in contact with the main prism 121, or a cubic prism with a square face in contact with the main prism 121. The secondary prism 125 corresponds to a specific example of the "second rectangular prism prism" in one embodiment of the present invention. The secondary prism 126 corresponds to a specific example of the "second rectangular prism prism" in one embodiment of the present invention.

[0061] The sub-prism 125 is capable of totally internalizing a portion of the transmitted light L11t (transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r, as described later) at its end face S12 facing the surface in contact with the main prism 121. In other words, the sub-prism 125 has an end face S12 that totally internalizes a portion of the transmitted light L11t (transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r, as described later). The sub-prism 126 is capable of totally internalizing a portion of the transmitted light L11t (transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r, as described later) at its end face S13 facing the surface in contact with the main prism 121. In other words, the sub-prism 126 has an end face S13 that causes total internal reflection of a portion of the transmitted light L11t (transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r, as described later).

[0062] The main prism 121 and the sub-prisms 124, 125, and 126 are all made of a common material. The main prism 121 and the sub-prisms 124, 125, and 126 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prisms 124, 125, and 126 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prisms 124, 125, and 126 may also be made of, for example, quartz or lithium tetraborate (LB4). The joining of the main prism 121 and the sub-prisms 124, 125, and 126 is performed, for example, by optical joining (optical contact). The joining of the main prism 121 and the sub-prisms 124, 125, and 126 may also be performed, for example, by adhesive joining or diffusion joining.

[0063] The partial reflective film 123a is provided between the main prism 121 and the sub-prism 124. The partial reflective film 123a is in contact with the end face S1 of the main prism 121 and the end face S9 of the sub-prism 124. The partial reflective film 123a is a beam splitter capable of splitting the pulsed laser light L1 into transmitted light and reflected light. The partial reflective film 123a has a film structure in which the transmittance is greater than the reflectance when the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°.

[0064] The partial reflective film 123a is capable of splitting pulsed laser light L1 into transmitted light L11t and reflected light L11r when pulsed laser light L1 is incident on the partial reflective film 123a as p-polarized light from the sub-prism 124 side at an incident angle of 45°. The partial reflective film 123a is capable of splitting transmitted light L11t into transmitted light L12t and reflected light L12r when transmitted light L11t, which has returned due to total internal reflection at the main prism 121, is incident on the main prism 121 side as p-polarized light at an incident angle of 45°. Transmitted light L12t is emitted in a direction coaxial with reflected light L11r. Reflected light L12r is emitted in a direction coaxial with transmitted light L11t.

[0065] When the reflected light L11r and transmitted light L12t are incident on the end face S8 of the sub-prism 124, they are totally reflected at the end face S8 of the sub-prism 124. The reflected light L11r and transmitted light L12t, which have been totally reflected at the end face S8 of the sub-prism 124, are incident on the partial reflective film 123a. The partial reflective film 123a is capable of splitting the reflected light L11r into transmitted light L111t and reflected light L111r when the reflected light L11r is incident on the sub-prism 124 side. The partial reflective film 123a is capable of splitting the transmitted light L12t into transmitted light L121t and reflected light L121r when the transmitted light L12t is incident on the sub-prism 124 side. The transmitted light L121t is emitted in a direction coaxial with the transmitted light L111t. The reflected light L121r is emitted in a direction coaxial with that of the reflected light L111r.

[0066] The partial reflective film 123a is capable of splitting transmitted light L111t into transmitted light L112t and reflected light L112r when transmitted light L111t, which has returned due to total internal reflection at the main prism 121 and sub-prisms 125, 126, is incident from the main prism 121 side as p-polarized light at an incident angle of 45°. Transmitted light L112t is emitted in a direction coaxial with reflected light L111r. Reflected light L112r is emitted in a direction coaxial with transmitted light L111t. The partial reflective film 123a is capable of splitting transmitted light L121t into transmitted light L122t and reflected light L122r when transmitted light L121t, which has returned due to total internal reflection at the main prism 121 and sub-prisms 125, 126, is incident from the main prism 121 side as p-polarized light at an incident angle of 45°. The transmitted light L122t is emitted in the same direction as the reflected light L111r. The reflected light L122r is emitted in the same direction as the transmitted light L111t.

[0067] Next, the effect of the time-division device 120 according to this modified example on the pulsed laser light L1 will be explained.

[0068] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prisms 124, 125, and 126 are made of calcium fluoride. In this case, the refractive index of the main prism 121 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. The total reflection angle of the end face S8 of the sub-prism 124 is 43.2°. The total reflection angle of the end face S12 of the sub-prism 125 is 43.2°. The total reflection angle of the end face S13 of the sub-prism 126 is 43.2°. The difference in optical path length between the path of transmitted light L11t and reflected light L12r propagating within the main prism 121 and the path of transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r propagating within the main prism 121 (optical path length difference) is 25 mm. In other words, the time delay corresponding to this optical path length difference is approximately 121.9 [ps].

[0069] When a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the main prism 121, a portion of the pulsed laser beam L1 is totally reflected at the end faces S2, S3, and S4. When a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 124, a portion of the pulsed laser beam L1 is totally reflected at the end face S8. When a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 125, a portion of the pulsed laser beam L1 is totally reflected at the end face S12. When a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 126, a portion of the pulsed laser beam L1 is totally reflected at the end face S13.

[0070] Let R be the reflectance of the partial reflective film 123a to pulsed laser light L1. The reflectance R is (1 - (R / 100)). 2 Assume that the value satisfying =R / 100 is 38.2%. The transmittance of the partial reflective film 123a to the pulsed laser light L1 is expressed as (100-R) and is 61.8%. The instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the transmitted light L11t is 61.8% of the instantaneous peak output of the pulsed laser light L1.

[0071] The reflected light L111r is the light obtained when the reflected light L11r is reflected by the partial reflective film 123a. The reflected light L11r is the light obtained when the pulsed laser light L1 is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L111r is 14.6% (=38.2% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0072] The reflected light L121r is the light obtained when the transmitted light L12t is reflected by the partial reflective film 123a. The transmitted light L12t is the light obtained when the transmitted light L11t passes through the partial reflective film 123a. The transmitted light L11t is the light obtained when the pulsed laser light L1 passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L121r is 14.6% (= 61.8% × 61.8% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0073] The transmitted light L112t is the light obtained when the transmitted light L111t passes through the partial reflective film 123a. The transmitted light L111t is the light obtained when the reflected light L11r passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L112t is 14.6% (=38.2% × 61.8% × 61.8%) of the instantaneous peak output of the pulsed laser light L1.

[0074] Transmitted light L122t is the light obtained when transmitted light L121t passes through the partial reflective film 123a. Transmitted light L121t is the light obtained when transmitted light L12t passes through the partial reflective film 123a. Therefore, the instantaneous peak output of transmitted light L122t is 14.6% (=61.8% × 61.8% × 61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1.

[0075] From the end face S11 of the sub-prism 124, a pulse train including reflected light L111r, transmitted light L112t, reflected light L121r, and transmitted light L122t is output, for example, as shown in Figure 9. The reflected light L121r is a pulse light that is delayed by the time required for transmitted light L11t to return to the partial reflective film 123a after total internal reflection at the main prism 121, compared to the time when reflected light L111r was generated. The time required for transmitted light L11t to return to the partial reflective film 123a after total internal reflection at the main prism 121 is called the delay time Δt1.

[0076] The transmitted light L112t is a pulsed light that occurs at a time delayed by the time it takes for the transmitted light L111r to return to the partial reflective film 123a after total internal reflection at the main prism 121 and sub-prisms 125 and 126, compared to the time it was generated. The time required for the transmitted light L111t to return to the partial reflective film 123a after total internal reflection at the main prism 121 and sub-prisms 125 and 126 is called the delay time Δt2. The transmitted light L122t is a pulsed light that occurs at a time delayed by the time it takes for the transmitted light L121r to return to the partial reflective film 123a after total internal reflection at the main prism 121 and sub-prisms 125 and 126, compared to the time it was generated. Therefore, the transmitted light L122t is a pulsed light that occurs at a time delayed by the delay time Δt1 + Δt2 compared to the time it was generated. The delay times Δt1, Δt2, and the difference between Δt1 and Δt2 are all at least longer than the pulse width of the pulsed laser light L1.

[0077] The light, including the pulse train output from the end face S11 of the sub-prism 124, becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only temporally divided within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 85.4% lower than the instantaneous peak output of the pulsed laser beam L1.

[0078] Next, the effects of the time-division device 120 according to this modified example will be explained.

[0079] In this modified example, the sub-prism 124 is an isosceles trapezoidal prism. The partial reflective film 123a is in contact with the end face S1 of the main prism 121 and the end face S9 of the sub-prism 124. In the sub-prism 124, the end face S10 is the incident surface for the pulsed laser light L1, and the end face S11 is the exit surface for the time-division pulsed laser light L2. This allows a portion of the pulsed laser light L1 to be efficiently transmitted into the interior of the main prism 121. Furthermore, the light transmitted into the interior of the main prism 121 (transmitted light L11t) can be incident on the end faces S2, S3, and S4 of the main prism 121 under total internal reflection conditions. Additionally, the light transmitted into the interior of the main prism 121 (transmitted light L111t) can be incident on the end face S4 of the main prism 121, the end face S12 of the sub-prism 125, and the end face S13 of the sub-prism 126 under total internal reflection conditions.

[0080] Furthermore, of the reflected light L11r, the light that has passed through the partial reflective film 123a twice (transmitted light L112t) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. Also, of the transmitted light L11t, the light that has passed through the partial reflective film 123a once and been reflected once by the partial reflective film 123a (reflected light L121r) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. Furthermore, of the transmitted light L11t, the light that has passed through the partial reflective film 123a three times (reflected light L122t) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. As a result, in relation to the pulsed laser light L1 incident on the composite prism, it is possible to obtain a time-resolved pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level.

[0081] In this modified example, multiple prisms are provided, including a main prism 121 and sub-prisms 124-126. This allows for the production of a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. As a result, it is possible to obtain a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0082] <Variation B> Figure 10 shows a modified configuration of the time-division device 120. Figure 11 is a diagram illustrating the optical operation of the time-division device 120 in Figure 10. In the above embodiment, the time-division device 120 may have a single sub-prism 124 instead of the sub-prism 122, as shown in Figure 10, and may further have a single sub-prism 127. The sub-prism 124 has the same configuration as the sub-prism 124 in modified example A. The sub-prism 124 corresponds to one specific example of the "multiple prisms" and "second prism" in one embodiment of the present invention. The sub-prism 127 corresponds to one specific example of the "second rectangular prism prism" and "fifth prism" in one embodiment of the present invention.

[0083] The sub-prism 127 is fixed to one of the end faces S2, S3, or S4 of the main prism 121, excluding the areas where the transmitted light L111t, reflected light L112r, transmitted light L121t, and reflected light L122r are totally reflected. Figure 10 shows an example where the sub-prism 127 is fixed to the end face S3 of the main prism 121. The sub-prism 127 is capable of totally reflecting a portion of the pulsed laser light L1 that has passed through the main prism 121 at the three end faces other than the one fixed to the main prism 121. In other words, the sub-prism 127 has three end faces that totally reflect a portion of the pulsed laser light L1 that has passed through the main prism 121.

[0084] The main prism 121 and the sub-prisms 124 and 127 are both made of a common material. The main prism 121 and the sub-prisms 124 and 127 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prisms 124 and 127 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prisms 124 and 127 may be made of, for example, quartz or lithium tetraborate (LB4). The joining of the main prism 121 and the sub-prism 127 is performed, for example, by optical joining (optical contact). The joining of the main prism 121 and the sub-prism 127 may also be performed, for example, by adhesive joining or diffusion joining.

[0085] Next, the effect of the time-division device 120 according to this modified example on the pulsed laser light L1 will be explained.

[0086] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prisms 124 and 127 are made of calcium fluoride. In this case, the refractive index of the main prism 121 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. The total reflection angle of the end face S8 of the sub-prism 124 is 43.2°. The total reflection angles of the three end faces of the sub-prism 127, excluding the end face in contact with the main prism 121, are 43.2°.

[0087] If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the main prism 121, a portion of the pulsed laser beam L1 will be totally reflected at the end faces S2, S3, and S4. If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 124, a portion of the pulsed laser beam L1 will be totally reflected at the end face S8. If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 127, a portion of the pulsed laser beam L1 will be totally reflected at the three end faces other than the end face in contact with the main prism 121.

[0088] Let R be the reflectance of the partial reflective film 123a to pulsed laser light L1. The reflectance R is (1 - (R / 100)). 2 Assume that the value satisfying =R / 100 is 38.2%. The transmittance of the partial reflective film 123a to the pulsed laser light L1 is expressed as (100-R) and is 61.8%. The instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the transmitted light L11t is 61.8% of the instantaneous peak output of the pulsed laser light L1.

[0089] The reflected light L111r is the light obtained when the reflected light L11r is reflected by the partial reflective film 123a. The reflected light L11r is the light obtained when the pulsed laser light L1 is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L111r is 14.6% (=38.2% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0090] The reflected light L121r is the light obtained when the transmitted light L12t is reflected by the partial reflective film 123a. The transmitted light L12t is the light obtained when the transmitted light L11t passes through the partial reflective film 123a. The transmitted light L11t is the light obtained when the pulsed laser light L1 passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L121r is 14.6% (= 61.8% × 61.8% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0091] The transmitted light L112t is the light obtained when the transmitted light L111t passes through the partial reflective film 123a. The transmitted light L111t is the light obtained when the reflected light L11r passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L112t is 14.6% (=38.2% × 61.8% × 61.8%) of the instantaneous peak output of the pulsed laser light L1.

[0092] Transmitted light L122t is the light obtained when transmitted light L121t passes through the partial reflective film 123a. Transmitted light L121t is the light obtained when transmitted light L12t passes through the partial reflective film 123a. Therefore, the instantaneous peak output of transmitted light L122t is 14.6% (=61.8% × 61.8% × 61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1.

[0093] From the end face S11 of the sub-prism 124, a pulse train including reflected light L111r, transmitted light L112t, reflected light L121r, and transmitted light L122t is output, for example, as shown in Figure 11. The reflected light L121r is a pulse light that is delayed by the time required for transmitted light L11t to return to the partial reflective film 123a after total internal reflection at the main prism 121, compared to the time when reflected light L111r was generated. The time required for transmitted light L11t to return to the partial reflective film 123a after total internal reflection at the main prism 121 is called the delay time Δt1.

[0094] The transmitted light L112t is a pulsed light that occurs at a time delayed by the time it takes for the transmitted light L111r to return to the partial reflective film 123a after total internal reflection within the main prism 121 and sub-prism 127, compared to the time when the reflected light L111r was generated. The time required for the transmitted light L111t to return to the partial reflective film 123a after total internal reflection within the main prism 121 and sub-prism 127 is called the delay time Δt2. The transmitted light L122t is a pulsed light that occurs at a time delayed by the time it takes for the transmitted light L121r to return to the partial reflective film 123a after total internal reflection within the main prism 121 and sub-prism 127, compared to the time when the reflected light L121r was generated. Therefore, the transmitted light L122t is a pulsed light that occurs at a time delayed by the delay time Δt1 + Δt2 compared to the time when the reflected light L111r was generated. The delay times Δt1, Δt2, and the difference between Δt1 and Δt2 are all at least longer than the pulse width of the pulsed laser light L1.

[0095] The light, including the pulse train output from the end face S11 of the sub-prism 124, becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only temporally divided within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 85.4% lower than the instantaneous peak output of the pulsed laser beam L1.

[0096] Next, the effects of the time-division device 120 according to this modified example will be explained.

[0097] In this modified example, the sub-prism 124 is an isosceles trapezoidal prism. The partial reflective film 123a is in contact with the end face S1 of the main prism 121 and the end face S9 of the sub-prism 124. In the sub-prism 124, the end face S10 is the incident surface for the pulsed laser light L1, and the end face S11 is the exit surface for the time-division pulsed laser light L2. This allows a portion of the pulsed laser light L1 to be efficiently transmitted into the interior of the main prism 121. Furthermore, the light transmitted into the interior of the main prism 121 (transmitted light L11t) can be incident on the end faces S2, S3, and S4 of the main prism 121 under total internal reflection conditions. Additionally, the light transmitted into the interior of the main prism 121 (transmitted light L111t) can be incident on the end face S4 of the main prism 121, the end face S12 of the sub-prism 125, and the end face S13 of the sub-prism 126 under total internal reflection conditions.

[0098] Furthermore, of the reflected light L11r, the light that has passed through the partial reflective film 123a twice (transmitted light L112t) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. Also, of the transmitted light L11t, the light that has passed through the partial reflective film 123a once and been reflected once by the partial reflective film 123a (reflected light L121r) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. Furthermore, of the transmitted light L11t, the light that has passed through the partial reflective film 123a three times (reflected light L122t) is output from the end face S11 of the sub-prism 122 by a predetermined time delay compared to when the reflected light L111r was output from the end face S11 of the sub-prism 124. As a result, in relation to the pulsed laser light L1 incident on the composite prism, it is possible to obtain a time-resolved pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level.

[0099] In this modified example, a main prism 121 and a sub-prism 127 are provided as multiple prisms. This allows for the production of a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. As a result, it is possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0100] <Variation C> Figure 12 shows one modified configuration of the time-division device 120. Figure 13 is a diagram illustrating the optical operation of the time-division device 120 in Figure 12. In the above modified configuration B, the time-division device 120 may further have a single sub-prism 128, for example, as shown in Figure 12. The sub-prism 128 corresponds to one specific example of the "second rectangular prism prism" and the "sixth prism" in one embodiment of the present invention.

[0101] The sub-prism 127 is fixed to the end face S2, S3, or S4 of the main prism 121, excluding the points where the optical paths P1 and P3 shown in Figure 13 enter. The sub-prism 128 is fixed to the end face S2, S3, or S4 of the main prism 121, excluding the points where the optical paths P1 and P2 shown in Figure 13 enter. Figure 12 shows an example where the sub-prism 127 is fixed to the end face S3 of the main prism 121. Figure 12 also shows an example where the sub-prism 128 is fixed to the end face S2 of the main prism 121. The sub-prism 128 is capable of totally reflecting a portion of the pulsed laser light L1 that has passed through the main prism 121 at the three end faces other than the end face to which it is fixed to the main prism 121. In other words, the sub-prism 128 has three end faces that cause a portion of the pulsed laser light L1 that has passed through the main prism 121 to undergo total internal reflection.

[0102] By adjusting the size of the sub-prism 127, it is possible to adjust the optical path length P2 of the light that undergoes total internal reflection within the sub-prism 127. By adjusting the size of the sub-prism 128, it is possible to adjust the optical path length P3 of the light that undergoes total internal reflection within the sub-prism 128. By making the optical path lengths of the three optical paths P1, P2, and P3 different from each other, the time delay amounts of each pulse obtained by time-division of the pulsed laser light L1 can be made different from each other. The time delay amount of each pulse obtained by time-division, and the difference between the time delay amounts of each pulse obtained by time-division, are at least greater than the pulse width of the pulsed laser light L1.

[0103] The main prism 121 and the sub-prisms 124, 127, and 128 are all made of a common material. The main prism 121 and the sub-prisms 124, 127, and 128 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prisms 124, 127, and 128 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prisms 124, 127, and 128 may also be made of, for example, quartz or lithium tetraborate (LB4). The joining of the main prism 121 and the sub-prisms 128 is performed, for example, by optical joining (optical contact). The joining of the main prism 121 and the sub-prisms 128 may also be performed, for example, by adhesive joining or diffusion joining.

[0104] Next, the effect of the time-division device 120 according to this modified example on the pulsed laser light L1 will be explained.

[0105] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prisms 124, 127, and 128 are made of calcium fluoride. In this case, the refractive index of the main prism 121 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. The total reflection angle of the end face S8 of the sub-prism 124 is 43.2°. The total reflection angles of the three end faces of the sub-prism 127 other than the end face in contact with the main prism 121 are 43.2°. The total reflection angles of the three end faces of the sub-prism 128 other than the end face in contact with the main prism 121 are 43.2°.

[0106] If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the main prism 121, a portion of the pulsed laser beam L1 will be totally reflected at the end faces S2, S3, and S4. If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 124, a portion of the pulsed laser beam L1 will be totally reflected at the end face S8. If a portion of the pulsed laser beam L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 127, a portion of the pulsed laser beam L1 will be totally reflected at the three end faces other than the end face in contact with the main prism 121. When a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45° on three end faces of the sub-prism 128 other than the end face in contact with the main prism 121, a portion of the pulsed laser light L1 is totally reflected by the three end faces other than the end face in contact with the main prism 121.

[0107] Let R be the reflectance of the partial reflective film 123a to pulsed laser light L1. The reflectance R is (1 - (R / 100)). 2 Assume that the value satisfying =R / 100 is 38.2%. The transmittance of the partial reflective film 123a to the pulsed laser light L1 is expressed as (100-R) and is 61.8%. The instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the transmitted light L11t is 61.8% of the instantaneous peak output of the pulsed laser light L1.

[0108] The instantaneous peak output of reflected light L111r is 14.6% (=38.2% × 38.2%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of transmitted light L111t is 23.6% (=38.2% × 61.8%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of reflected light L121r is 14.6% (=61.8% × 61.8% × 38.2%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of transmitted light L121t is 23.6% (=61.8% × 61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of transmitted light L112t is 14.6% (=38.2% × 61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1. The instantaneous peak output of transmitted light L122t is 14.6% (=61.8% × 61.8% × 61.8% × 61.8%) of the instantaneous peak output of pulsed laser light L1.

[0109] Reflected light L111r is partially reflected by the partial reflective film 123a, resulting in reflected light L1111r. Transmitted light L112t is partially reflected by the partial reflective film 123a, resulting in reflected light L1121r. Reflected light L121r is partially reflected by the partial reflective film 123a, resulting in reflected light L1211r. Transmitted light L122t is partially reflected by the partial reflective film 123a, resulting in reflected light L1221r. Reflected light L1121r, reflected light L1211r, and reflected light L1221r are emitted in a direction coaxial with reflected light L1111r. The instantaneous peak output of each of the reflected light beams L1111r, L1121r, L1211r, and L1221r is 5.58% (= 14.6% × 38.2%) of the instantaneous peak output of the pulsed laser beam L1.

[0110] A pulse train containing at least reflected light L1111r, reflected light L1121r, reflected light L1211r, and reflected light L1221r is output from the end face S11 of the sub-prism 124. Here, at least the delay times of reflected light L1121r, reflected light L1211r, and reflected light L1221r relative to reflected light L1111r are different from each other. The delay times of reflected light L1121r, reflected light L1211r, and reflected light L1221r relative to reflected light L1111r are at least greater than the pulse width of pulsed laser light L1. The difference between the delay times of reflected light L1121r, reflected light L1211r, and reflected light L1221r relative to reflected light L1111r is at least greater than the pulse width of pulsed laser light L1.

[0111] The light, including the pulse train output from the end face S11 of the sub-prism 124, becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only temporally divided within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 85.4% lower than the instantaneous peak output of the pulsed laser beam L1.

[0112] Next, the effects of the time-division device 120 according to this modified example will be explained.

[0113] In this modified example, multiple prisms are provided, including a main prism 121 and sub-prisms 127 and 128. This allows for the production of a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. As a result, it is possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0114] <Variation D> Figure 14 shows a modified configuration of the time-division device 120. Figure 15 is a diagram illustrating the optical operation of the time-division device 120 in Figure 14. In the above embodiment, the time-division device 120 may further include a partial reflective film 123d and a sub-prism 127, for example, as shown in Figure 14. The partial reflective film 123d corresponds to one specific example of the "one or more partial reflective films" or "second partial reflective film" in one embodiment of the present invention. The sub-prism 127 corresponds to one specific example of the "second rectangular prism prism" in one embodiment of the present invention.

[0115] The partial reflective film 123d is provided between the main prism 121 and the sub-prism 127. The partial reflective film 123d is in contact with the end face S2, end face S3, or end face S4 of the main prism 121. Figure 14 shows an example where the partial reflective film 123d is in contact with the end face S3 of the main prism 121. The sub-prism 127 is fixed to the end face S2, end face S3, or end face S4 of the main prism 121. The sub-prism 127 is fixed to the end face S2, end face S3, or end face S4 of the main prism 121 where the partial reflective film 123d is provided. Figure 14 shows an example where the sub-prism 127 is fixed to the end face S3 of the main prism 121 via the partial reflective film 123d.

[0116] The sub-prism 127 is capable of totally reflecting a portion of the pulsed laser light L1 that has passed through the main prism 121 at three end faces other than the end face fixed to the main prism 121. In other words, the sub-prism 127 has three end faces that totally reflect a portion of the pulsed laser light L1 that has passed through the main prism 121.

[0117] The main prism 121 and the sub-prisms 124 and 127 are both made of a common material. The main prism 121 and the sub-prisms 124 and 127 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prisms 124 and 127 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prisms 124 and 127 may be made of, for example, quartz or lithium tetraborate (LB4). The joining of the main prism 121 and the sub-prism 127 is performed, for example, by optical joining (optical contact). The joining of the main prism 121 and the sub-prism 127 may also be performed, for example, by adhesive joining or diffusion joining.

[0118] The partially reflective film 123d is a beam splitter capable of splitting a portion of the pulsed laser light L1 into transmitted and reflected light. The partially reflective film 123d has a film structure in which the transmittance is greater than the reflectance when a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°.

[0119] The partial reflective film 123d is capable of splitting a portion of the pulsed laser light L1 into transmitted light L14t and reflected light L14r when a portion of the pulsed laser light L1 is incident as p-polarized light from the main prism 121 side at an incident angle of 45°. The partial reflective film 123d is also capable of splitting the transmitted light L14t, which has returned due to total internal reflection by the sub-prism 127, into transmitted light L16t and reflected light L16r when it is incident as p-polarized light from the sub-prism 127 side at an incident angle of 45°.

[0120] The partially reflective film 123a has a film structure in which the transmittance is greater than the reflectance when pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°. The partially reflective film 123a is capable of splitting pulsed laser light L1 into transmitted light L11t and reflected light L11r when pulsed laser light L1 is incident as p-polarized light from the sub-prism 122 side at an incident angle of 45°. The partially reflective film 123a is capable of splitting transmitted light L14t into transmitted light L15t and reflected light L15r when transmitted light L14t, which has returned due to total internal reflection by the main prism 121 and sub-prism 122, is incident as p-polarized light from the main prism 121 side at an incident angle of 45°. The partial reflective film 123a is capable of splitting the reflected light L16r, which has returned due to total internal reflection by the main prism 121 and the sub-prism 122, into transmitted light L17t and reflected light L17r when the reflected light L16r is incident from the main prism 121 side as p-polarized light at an incident angle of 45°.

[0121] Next, the effect of the time-division device 120 according to this modified example on the pulsed laser light L1 will be explained.

[0122] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prisms 122 and 127 are made of calcium fluoride. In this case, the refractive index of the main prism 121 and the sub-prisms 122 and 127 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. Assume that transmitted light L14t, reflected light L15r, and transmitted light L16t are incident as p-polarized light at an incident angle of 45° on the unfixed end face of the sub-prism 127 among the end faces S2, S3, and S4. In this case, the transmitted light L14t, reflected light L15r, and transmitted light L16t are totally reflected at the unfixed end face of the sub-prism 127 among the end faces S2, S3, and S4.

[0123] The total reflection angle of the three end faces of the sub-prism 127, excluding the end face fixed to the main prism 121, is 43.2°. Assume that transmitted light L14t and reflected light L16r are incident as p-polarized light at an incident angle of 45° on the three end faces of the sub-prism 127, excluding the end face fixed to the main prism 121. In this case, the transmitted light L14t and reflected light L16r are totally reflected at the three end faces excluding the end face fixed to the main prism 121.

[0124] Let R1 be the reflectance of the partial reflective film 123a to the pulsed laser light L1. Let R2 be the reflectance of the partial reflective film 123d to the pulsed laser light L1. In this case, the reflectances R1 and R2 are (1 - (R1 / 100)). 2 ×(1-(R2 / 100)) 2 Assume that the value satisfies =R / 100. When R1=R2, R1 and R2 are 27.6%. The transmittance of the partial reflective films 123a and 123d to pulsed laser light L1 is expressed as (100-R). When R1=R2, the transmittance of the partial reflective films 123a and 123d to pulsed laser light L1 is 72.4%. The following explanation assumes that R1=R2. The instantaneous peak output of the reflected light L11r is 27.6% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the transmitted light L11t is 72.4% of the instantaneous peak output of the pulsed laser light L1.

[0125] The transmitted light L14t is the light obtained when the transmitted light L11t passes through the partial reflective film 123d. Therefore, the instantaneous peak output of the transmitted light L14t is 52.4% (=72.4% × 72.4%) of the instantaneous peak output of the pulsed laser light L1. The reflected light L14r is the light obtained when the transmitted light L11t is reflected by the partial reflective film 123d. Therefore, the instantaneous peak output of the transmitted light L14r is 20.0% (=72.4% × 27.6%) of the instantaneous peak output of the pulsed laser light L1.

[0126] The transmitted light L15t is the light obtained when the reflected light L14r passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L15t is 14.5% (=72.4% × 27.6% × 72.4%) of the instantaneous peak output of the pulsed laser light L1. The reflected light L15r is the light obtained when the reflected light L14r is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L15r is 5.5% (=72.4% × 27.6% × 27.6%) of the instantaneous peak output of the pulsed laser light L1.

[0127] Transmitted light L16t is the light obtained when transmitted light L14t passes through the partial reflective film 123d. Therefore, the instantaneous peak output of transmitted light L16t is 38.0% (=72.4% × 72.4% × 72.4%) of the instantaneous peak output of pulsed laser light L1. Transmitted light L17t is the light obtained when transmitted light L16t passes through the partial reflective film 123d. Therefore, the instantaneous peak output of transmitted light L17t is 27.5% (=72.4% × 72.4% × 72.4% × 72.4%) of the instantaneous peak output of pulsed laser light L1.

[0128] From the end face S6 of the sub-prism 122, a pulse train including reflected light L11r, transmitted light L15t, and transmitted light L17t is output, for example, as shown in Figure 15. Transmitted light L15t is a pulse light that is delayed by Δt1 time compared to the time when the reflected light L11r was generated, by the time required for the transmitted light L11t to return to the partial reflective film 123a after total reflection at the main prism 121 and partial reflection at the partial reflective film 123b. Transmitted light L17t is a pulse light that is delayed by Δt2 time compared to the time when the reflected light L11r was generated, by the time required for the transmitted light L11t to return to the partial reflective film 123a after total reflection at the main prism 121 and sub-prism 127 and partial transmission at the partial reflective film 123b.

[0129] Time Δt2 is longer than time Δt1 by the length of the optical path within the sub-prism 127. Time Δt1, time Δt2, and the difference between Δt1 and time Δt2 are all at least greater than the pulse width of the pulsed laser light L1.

[0130] The light, including the pulse train output from the end face S6 of the sub-prism 122, becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only divided in time within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 72.4% lower than the instantaneous peak output of the pulsed laser beam L1.

[0131] Next, the effects of the time-division device 120 according to this modified example will be explained.

[0132] In this modified example, multiple prisms are provided, including a main prism 121 and sub-prisms 122 and 127. A partial reflective film 123a is provided between the main prism 121 and the sub-prism 122. A partial reflective film 123d is provided between the main prism 121 and the sub-prism 127. As a result, a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output is obtained compared to the pulsed laser beam L1 incident on the composite prism, without causing a decrease in the time-averaged output level. Consequently, a time-division pulsed laser beam L2 with a higher pulse repetition frequency and lower instantaneous peak output can be obtained while maintaining the time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0133] <Variation E> Figure 16 shows one modified configuration of the time-division device 120. Figure 17 is a diagram illustrating the optical operation of the time-division device 120 in Figure 16. In the above modified configuration B, the time-division device 120 may further include, for example, a partial reflective film 123e and a single sub-prism 129, as shown in Figure 16. The partial reflective film 123e corresponds to one specific example of "one or more partial reflective films" or "second partial reflective film" in one embodiment of the present invention. The sub-prism 129 corresponds to one specific example of "second rectangular prism prism" or "seventh prism" in one embodiment of the present invention.

[0134] The partial reflective film 123e is provided between the sub-prism 124 and the sub-prism 129. The partial reflective film 123e is in contact with the end face S8 of the sub-prism 124 and the end face of the sub-prism 129 on the sub-prism 124 side. The sub-prism 127 is fixed to the end face S8 of the sub-prism 124 via the partial reflective film 123e.

[0135] The sub-prism 129 is capable of totally reflecting a portion of the pulsed laser light L1 that has passed through the sub-prism 127 at three end faces other than the end face fixed to the sub-prism 127. In other words, the sub-prism 129 has three end faces that totally reflect a portion of the pulsed laser light L1 that has passed through the sub-prism 127.

[0136] The main prism 121 and the sub-prisms 124, 127, and 129 are all made of a common material. The main prism 121 and the sub-prisms 124, 127, and 129 are made of, for example, calcium fluoride (CaF2). The material of the main prism 121 and the sub-prisms 124, 127, and 129 is not limited to calcium fluoride, but can be appropriately selected depending on the wavelength, intensity, and transmittance of the pulsed laser light L1. The main prism 121 and the sub-prisms 124, 127, and 129 may also be made of, for example, quartz or lithium tetraborate (LB4). The joining of the sub-prism 124 and the sub-prism 129 is performed, for example, by optical joining (optical contact). The joining of the sub-prism 124 and the sub-prism 129 may also be performed, for example, by adhesive joining or diffusion joining.

[0137] The partially reflective film 123e is a beam splitter capable of splitting a portion of the pulsed laser light L1 into transmitted and reflected light. The partially reflective film 123e has a film structure in which the transmittance is greater than the reflectance when a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°.

[0138] The partial reflective film 123e is capable of splitting a portion of the pulsed laser light L1 into transmitted light L14t and reflected light L14r when a portion of the pulsed laser light L1 is incident as p-polarized light from the sub-prism 124 side at an incident angle of 45°. The partial reflective film 123e is capable of splitting the transmitted light L14t into transmitted light L16t and reflected light L16r when the transmitted light L14t that has returned due to total internal reflection by the sub-prism 129 is incident as p-polarized light from the sub-prism 129 side at an incident angle of 45°. The partial reflective film 123e is capable of splitting the transmitted light L18t obtained by repeated total internal reflection by the main prism 121, etc., into transmitted light L19t and reflected light L19r when the transmitted light L18t is incident as p-polarized light from the sub-prism 124 side at an incident angle of 45°. The partial reflective film 123e is capable of splitting transmitted light L19t into transmitted light L21t and reflected light L21r when transmitted light L19t, which has returned due to total internal reflection by the sub-prism 129, is incident from the sub-prism 129 side as p-polarized light at an incident angle of 45°.

[0139] The partially reflective film 123a has a film structure in which the transmittance is greater than the reflectance when pulsed laser light L1 is incident as p-polarized light at an incident angle of 45°. The partially reflective film 123a is capable of splitting pulsed laser light L1 into transmitted light L11t and reflected light L11r when pulsed laser light L1 is incident as p-polarized light from the sub-prism 124 side at an incident angle of 45°. The partially reflective film 123a is capable of splitting transmitted light L11t into transmitted light L18t and reflected light L18r when transmitted light L11t, which has returned due to total internal reflection by the main prism 121, is incident as p-polarized light from the main prism 121 side at an incident angle of 45°. The partial reflective film 123a is capable of splitting the reflected light L14r, which has returned due to partial reflection by the partial reflective film 123e, into transmitted light L15t and reflected light L15r when it is incident as p-polarized light from the sub-prism 124 side at an incident angle of 45°.

[0140] The partial reflective film 123a is capable of splitting the reflected light L16t into transmitted light L17t and reflected light L17r when transmitted light L16t, which has returned due to total internal reflection by the sub-prism 129, is incident from the sub-prism 124 side as p-polarized light at an incident angle of 45°. The partial reflective film 123a is capable of splitting the reflected light L19r into transmitted light L20t and reflected light L20r when reflected light L19r, which has returned due to partial reflection by the partial reflective film 123e, is incident from the sub-prism 124 side as p-polarized light at an incident angle of 45°. The partial reflective film 123a is capable of splitting the reflected light L21t into transmitted light L22t and reflected light L22r when transmitted light L21t, which has returned due to total internal reflection by the sub-prism 129, is incident from the sub-prism 124 side as p-polarized light at an incident angle of 45°.

[0141] Next, the effect of the time-division device 120 according to this modified example on the pulsed laser light L1 will be explained.

[0142] Assume the wavelength of the pulsed laser light L1 is 266 nm. Furthermore, assume that the main prism 121 and the sub-prisms 124, 127, and 129 are made of calcium fluoride. In this case, the refractive index of the main prism 121 is 1.4621. The total reflection angles of the end faces S2, S3, and S4 of the main prism 121 are 43.2°. The total reflection angles of the three end faces of the sub-prism 127, excluding the end face fixed to the main prism 121, are 43.2°. The total reflection angles of the three end faces of the sub-prism 129, excluding the end face fixed to the sub-prism 127, are 43.2°.

[0143] If a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45° within the main prism 121, a portion of the pulsed laser light L1 will be totally internalized at the end faces S2, S3, and S4. If a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 127, a portion of the pulsed laser light L1 will be totally internalized at the three end faces other than the one fixed to the main prism 121 within the sub-prism 127. If a portion of the pulsed laser light L1 is incident as p-polarized light at an incident angle of 45° within the sub-prism 129, a portion of the pulsed laser light L1 will be totally internalized at the three end faces other than the one fixed to the sub-prism 124 within the sub-prism 129.

[0144] Let R be the reflectance of the partial reflective film 123a to pulsed laser light L1. The reflectance R is (1 - (R / 100)). 2 Assume that the value satisfying =R / 100 is 38.2%. The transmittance of the partial reflective film 123a to the pulsed laser light L1 is expressed as (100-R) and is 61.8%. The instantaneous peak output of the reflected light L11r is 38.2% of the instantaneous peak output of the pulsed laser light L1. The instantaneous peak output of the transmitted light L11t is 61.8% of the instantaneous peak output of the pulsed laser light L1. The transmitted light L18t is the light obtained when the transmitted light L11t passes through the partial reflective film 123a. Therefore, the instantaneous peak output of the transmitted light L18t is 38.2% (=61.8% × 61.8%) of the instantaneous peak output of the pulsed laser light L1.

[0145] The reflected light L15r is the light obtained when the reflected light L14r is reflected by the partial reflective film 123a. The reflected light L14r is the light obtained when the pulsed laser light L1 is reflected by the partial reflective film 123a. Therefore, the instantaneous peak output of the reflected light L15r is 14.6% (=38.2% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0146] The reflected light L17r is the light obtained when the transmitted light L16t is reflected by the partial reflective film 123a. The transmitted light L16t is the light obtained when the transmitted light L14t is transmitted through the partial reflective film 123e. The transmitted light L14t is the light obtained when the reflected light L11r is transmitted through the partial reflective film 123e. Therefore, the instantaneous peak output of the reflected light L17r is 5.6% (=38.2% × 61.8% × 61.8% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0147] The reflected light L20r is the light obtained when the reflected light L19r is reflected by the partial reflective film 123a. The reflected light L19r is the light obtained when the transmitted light L18t is reflected by the partial reflective film 123e. The transmitted light L18t is the light obtained when the transmitted light L11t passes through the partial reflective film 123e. Therefore, the instantaneous peak output of the reflected light L20r is 5.6% (= 61.8% × 61.8% × 38.2% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0148] The reflected light L22r is the light obtained when the transmitted light L21t is reflected by the partial reflective film 123a. The transmitted light L21t is the light obtained when the transmitted light L19t is transmitted through the partial reflective film 123e. The transmitted light L19t is the light obtained when the transmitted light L18t is transmitted through the partial reflective film 123e. Therefore, the instantaneous peak output of the reflected light L22r is 5.6% (= 61.8% × 61.8% × 61.8% × 61.8% × 38.2%) of the instantaneous peak output of the pulsed laser light L1.

[0149] From the end face S11 of the sub-prism 124, a pulse train including reflected light L15r, reflected light L17r, reflected light L20r, and reflected light L22t is output, for example, as shown in Figure 17. Reflected light L17r is a pulse light generated at a time delayed by the time required for transmitted light L14t to return to the partial reflective film 123e after total internal reflection at the sub-prism 129, compared to the time reflected light L15r was generated. Reflected light L20r is a pulse light generated at a time delayed by the time required for transmitted light L11t to return to the partial reflective film 123a after total internal reflection at the main prism 121, compared to the time reflected light L15r was generated. The time required for transmitted light L11r to return to the partial reflective film 123a after total internal reflection at the main prism 121 is called the delay time Δt1. The reflected light L22t is a pulsed light generated at a time delayed by the time required for the transmitted light L19t to return to the partial reflective film 123e via total internal reflection at the sub-prism 129, compared to the time when the reflected light L20r was generated. The time required for the transmitted light L19t to return to the partial reflective film 123e via total internal reflection at the sub-prism 129 is called the delay time Δt2. Therefore, the reflected light L22t is a pulsed light generated at a time delayed by the time when the reflected light L15r was generated by the delay time Δt1 + Δt2. The delay times Δt1, Δt2, and the difference between delay times Δt1 and Δt2 are at least greater than the pulse width of the pulsed laser light L1.

[0150] The light, including the pulse train output from the end face S11 of the sub-prism 124, becomes the time-division pulsed laser beam L2. Since the pulsed laser beam L1 is only temporally divided within the composite prism, the time-averaged output level of the time-division pulsed laser beam L2 is approximately equal to the time-averaged output level of the pulsed laser beam L1. The instantaneous peak output of the time-division pulsed laser beam L2 is 94.6% lower than the instantaneous peak output of the pulsed laser beam L1.

[0151] <Modification F> Figure 18 shows a modified configuration of the time-division device 120. In the modified configuration A described above, the time-division device 120 may have a prism 141 instead of the main prism 121 and the sub-prisms 125 and 126, as shown in Figure 18. The prism 141 is a single prism having the same function as the main prism 121 and the sub-prisms 125 and 126. The prism 141 corresponds to a specific example of the "first prism" in one embodiment of the present invention.

[0152] The prism 141 has an end face S1 to which the sub-prism 124 is fixed, an end face S2 parallel to end face S1, and end faces S3 and S4 perpendicular to end face S1. In the prism 141, a convex portion 141a is provided on a part of end face S2, which has an end face that causes total internal reflection of the transmitted light of the pulsed laser light L1 that has passed through the partial reflective film 123a. In the prism 141, a convex portion 141b is provided on a part of end face S3, which has an end face that causes total internal reflection of the transmitted light. The convex portion 141a corresponds to a specific example of the "first rectangular prism-shaped convex portion" of one embodiment of the present invention. The convex portion 141b corresponds to a specific example of the "second rectangular prism-shaped convex portion" of one embodiment of the present invention.

[0153] In this modified example, the composite prism is capable of generating time-resolved pulsed laser light L2 through partial reflection and partial transmission at the partial reflective film 123a, and total reflection at the convex portions 141a, 141b, and end face S4.

[0154] In this modified example, a prism 141 having the same function as the main prism 121 and the sub-prisms 125 and 126 is provided. This makes it possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism, similar to modified example A above.

[0155] <Extreme Variation G> Figure 19 shows a modified configuration of the time-division device 120. In the modified configuration B described above, the time-division device 120 may have a prism 142 instead of the main prism 121 and the sub-prism 127, as shown in Figure 19. The prism 142 is a single prism having the same function as the main prism 121 and the sub-prism 127. The prism 142 corresponds to a specific example of the "first prism" in one embodiment of the present invention.

[0156] The prism 142 has an end face S1 to which the sub-prism 124 is fixed, an end face S2 parallel to end face S1, and end faces S3 and S4 perpendicular to end face S1. In the prism 142, a convex portion 142a is provided on part of end face S2, end face S3, or end face S4, having three end faces that cause total internal reflection of the transmitted light of the pulsed laser light L1 that has passed through the partial reflective film 123a. Figure 19 shows an example in which the convex portion 142a is provided on part of end face S3. The convex portion 142a corresponds to a specific example of the "first quadrangular prism-shaped convex portion" of one embodiment of the present invention.

[0157] In this modified example, the composite prism is capable of generating time-resolved pulsed laser light L2 through partial reflection and partial transmission at the partial reflective film 123a, total reflection at the convex portion 142a, and total reflection at the end face S2, S3, and S4 where the convex portion 142a is not formed.

[0158] In this modified example, a prism 142 having the same function as the main prism 121 and the sub-prism 127 is provided. This makes it possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism.

[0159] <Variation H> Figure 20 shows a modified configuration of the time-division device 120. In the modified configuration C described above, the time-division device 120 may have a prism 143 instead of the main prism 121 and sub-prisms 127, 128, as shown in Figure 20. The prism 143 is a single prism having the same function as the main prism 121 and sub-prisms 127, 128. The prism 143 corresponds to a specific example of the "first prism" in one embodiment of the present invention.

[0160] The prism 143 has an end face S1 to which the sub-prism 124 is fixed, an end face S2 parallel to end face S1, and end faces S3 and S4 perpendicular to end face S1. In the prism 143, a convex portion 142a is provided on part of end face S2, end face S3, or end face S4, having three end faces that cause total internal reflection of the transmitted light of the pulsed laser beam L1 that has passed through the partial reflective film 123a. Figure 20 shows an example in which the convex portion 142a is provided on part of end face S3. Furthermore, in the prism 143, a convex portion 142b is provided on part of end face S2, end face S3, or end face S4, having three end faces that cause total internal reflection of the transmitted light of the pulsed laser beam L1 that has passed through the partial reflective film 123a. Figure 20 shows an example in which the convex portion 142b is provided on part of end face S2. The protrusion 142a corresponds to a specific example of the "first quadrangular prism-shaped protrusion" of one embodiment of the present invention. The protrusion 142b corresponds to a specific example of the "second quadrangular prism-shaped protrusion" of one embodiment of the present invention.

[0161] In this modified example, the composite prism is capable of generating time-resolved pulsed laser light L2 through partial reflection and partial transmission at the partial reflective film 123a, total reflection at the convex portion 142a, total reflection at the convex portion 142b, and total reflection at the end faces S2, S3, and S4 where the convex portions 142a and 142b are not formed.

[0162] In this modified example, a prism 143 having the same function as the main prism 121 and the sub-prisms 127 and 128 is provided. This makes it possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism, similar to modified example C described above.

[0163] <Differentiation Example I> Figure 21 shows a modified configuration of the time-division device 120. In the modified configuration E described above, the time-division device 120 may have a prism 144 instead of the main prism 121 and the sub-prism 127, as shown in Figure 21. The prism 144 is a single prism having the same function as the main prism 121 and the sub-prism 127. The prism 144 corresponds to a specific example of the "first prism" in one embodiment of the present invention.

[0164] The prism 144 has an end face S1 to which the sub-prism 124 is fixed, an end face S2 parallel to end face S1, and end faces S3 and S4 perpendicular to end face S1. In the prism 144, a convex portion 142a is provided on part of end face S2, end face S3, or end face S4, having three end faces that cause total internal reflection of the transmitted light from the pulsed laser beam L1 that has passed through the partially reflective film 123a. Figure 21 shows an example in which the convex portion 142a is provided on part of end face S3. The convex portion 142a corresponds to a specific example of the "first quadrangular prism-shaped convex portion" of one embodiment of the present invention.

[0165] In this modified example, the composite prism is capable of generating time-resolved pulsed laser light L2 through partial reflection and partial transmission at the partial reflective film 123a, total reflection at the convex portion 142a, and total reflection at the end face S2, S3, and S4 where the convex portion 142a is not formed.

[0166] In this modified example, a prism 143 having the same function as the main prism 121 and the sub-prisms 127 and 128 is provided. This makes it possible to obtain a time-division pulsed laser beam L2 with a high pulse repetition frequency and low instantaneous peak output while maintaining a time-averaged output level in relation to the pulsed laser beam L1 incident on the composite prism, similar to modified example E above.

[0167] <Variation J> In the above embodiments and modifications A to I, the pulsed laser light L1 may be incident on the interface of the main prism 121 or the like as s-polarized light. In this case, "p-polarized light" as described in the above embodiments and modifications A to I shall be read as "s-polarized light". In this way, even when the pulsed laser light L1 is incident on the interface of the main prism 121 or the like as s-polarized light, a time-division pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output can be obtained with a small number of parts while maintaining a time-averaged output level in relation to the pulsed laser light L1 incident on the composite prism.

[0168] <Extreme Variation K> In the above embodiments and modifications A to I, the pulsed laser light L1 may be circularly polarized light. In this case, "p-polarized light" as described in the above embodiments and modifications A to I shall be read as "circularly polarized light". In this modification, the pulsed laser light source 110 further includes an optical element capable of converting laser light output from, for example, a wavelength conversion type light source into circularly polarized light. The pulsed laser light source 110 outputs pulsed laser light L1 which is circularly polarized.

[0169] In this modified example, the pulsed laser light L1 is circularly polarized light. Even in this case, similar to the above embodiment and modified examples A to I, a time-division pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output can be obtained with a small number of components while maintaining the time-averaged output level in relation to the pulsed laser light L1 incident on the composite prism.

[0170] <Modified form L> In the above embodiments and modifications A to I, the pulsed laser light L1 may be unpolarized light. In this case, "p-polarized light" as described in the above embodiments and modifications A to I shall be read as "unpolarized light". In this modification, the pulsed laser light source 110 further includes an optical element capable of converting laser light output from, for example, a wavelength conversion type light source into unpolarized light. The pulsed laser light source 110 outputs unpolarized pulsed laser light L1.

[0171] In this modified example, the pulsed laser light L1 is unpolarized light. Even in this case, similar to the above embodiment and modified examples A to I, a time-division pulsed laser light L2 with a high pulse repetition frequency and low instantaneous peak output can be obtained with a small number of components while maintaining a time-averaged output level in relation to the pulsed laser light L1 incident on the composite prism.

[0172] The effects described herein are for illustrative purposes only. The effects of this disclosure are not limited to those described herein. This disclosure may have effects other than those described herein.

[0173] Furthermore, for example, this disclosure can take the following form. <1> A light source (110) capable of outputting pulsed laser light (L1), A composite prism (120) is formed by integrating multiple prisms (121-129, 141-144) and one or more partial reflective films (123a, 123d, 123e) Equipped with, The composite prism (120) divides the incident pulsed laser light (L1) in time within the composite prism (120) through total internal reflection in the plurality of prisms (121-129, 141-144) and partial internal reflection and partial transmission in the one or more partial reflective films (123a, 123d, 123e). This enables the generation and output of time-division pulsed laser light (L2), in which the pulsed light contained in the pulsed laser light (L1) is divided in time. Light source device (a device composed of 110 and 120). <2> The composite prism (120) includes, as the plurality of prisms (121-129, 141-144), a first prism (121, 141-144) and a second prism (122, 124) fixed to the first prism (121, 141-144). In the one or more partial reflective films (123a, 123d, 123e) described above, the first partial reflective film (123a) is provided between the first prism (121, 141-144) and the second prism (122, 124), and is capable of splitting the pulsed laser light (L1) into transmitted light and reflected light. <1> The light source device described in (a device composed of 110 and 120). <3> The first prism (121) is a first rectangular prism having a first end face (S1) to which the second prism (122) is fixed, a second end face (S2) parallel to the first end face (S1), and a third end face (S3) and a fourth end face (S4) perpendicular to the first end face (S1). The composite prism (120) is capable of generating the time-resolved pulsed laser light (L2) through partial reflection and partial transmission at the one or more partial reflective films (123a, 123d, 123e) and total reflection at the second end face (S2), the third end face (S3), and the fourth end face (S4). <2> The light source device described in (a device composed of 110 and 120). <4> The second prism (122) is a right-angle prism, The right-angle prism has a fifth end face (S5) and a sixth end face (S6) that are orthogonal to each other, and a seventh end face (S7) connected to the fifth end face (S5). The first partial reflective film (123a) is in contact with the first end face (S1) and the seventh end face (S7), The fifth end face (S5) is the incident surface of the pulsed laser light (L1), The sixth end face (S6) is the emission surface of the time-resolved pulsed laser light (L2). <3> The light source device described in (a device composed of 110 and 120). <5> The second prism (122) is an isosceles trapezoidal prism, The isosceles trapezoidal prism has an eighth end face (S8) corresponding to the upper base of the trapezoid, a ninth end face (S9) corresponding to the lower base of the trapezoid, and a tenth end face (S10) and an eleventh end face (S11) corresponding to the legs of the trapezoid. The first partial reflective film (123a) is in contact with the first end face (S1) and the ninth end face (S9), The tenth end face (S10) is the incident surface of the pulsed laser light (L1), The 11th end face (S11) is the emission surface of the time-resolved pulsed laser light (L2). <3> The light source device described in (a device composed of 110 and 120). <6> The composite prism (120) includes, as the plurality of prisms (121-129), the first prism (121), the second prism (124), and one or more second rectangular prism-shaped prisms (125-129) fixed to the first prism (121) or the second prism (124) to provide a time delay. <5> The light source device described in (a device composed of 110 and 120). <7> The composite prism (120) includes, as the plurality of second rectangular prism-shaped prisms (125-129), a third prism (125) fixed to the second end face (S2) and having an end face that totally reflects the transmitted light, and a fourth prism (126) fixed to the third end face (S3) and having an end face that totally reflects the transmitted light. <6> The light source device described in (a device composed of 110 and 120). <8> The composite prism (120) includes a fifth prism (127) which is fixed to the second end face (S2), the third end face (S3), or the fourth end face (S4) as a single second rectangular prism (127), and has three end faces that cause total internal reflection of the transmitted light. <6> The light source device described in (a device composed of 110 and 120). <9> The composite prism (120) includes, as the plurality of second rectangular prism-shaped prisms (125-129), a fifth prism (127) fixed to the second end face (S2), the third end face (S3), or the fourth end face (S4) and having three end faces that cause total internal reflection of the transmitted light, and a sixth prism (128) fixed to the second end face (S2), the third end face (S3), or the fourth end face (S4) and having three end faces that cause total internal reflection of the transmitted light. <6> The light source device described in (a device composed of 110 and 120). <10> The composite prism (120) includes, as the plurality of second rectangular prism-shaped prisms (125-129), a seventh prism (129) fixed to the eighth end face (S8) and having three end faces that cause total internal reflection of the transmitted light, and a fifth prism (127) fixed to the second end face (S2), the third end face (S3), or the fourth end face (S4) and having three end faces that cause total internal reflection of the transmitted light. The second partial reflective film (123e) among the plurality of partial reflective films (123a, 123d, 123e) is provided between the second prism (124) and the seventh prism (129), and is capable of splitting the pulsed laser light (L1) into transmitted light and reflected light. <6> The light source device described in (a device composed of 110 and 120). <11> The composite prism (120) includes, as the plurality of prisms (125-129), the first prism (121), the second prism (122), and a second rectangular prism-shaped prism (127) fixed to the first prism (121) and providing a time delay. The second partial reflective film (123d) in the plurality of partial reflective films (123a, 123d, 123e) is provided between the first prism (121) and the second rectangular prism-shaped prism (127), and is capable of splitting the pulsed laser light (L1) into transmitted light and reflected light. <4> The light source device described in (a device composed of 110 and 120). <12> The first prism (141) has a first end face (S1) to which the second prism (124) is fixed, a second end face (S2) parallel to the first end face (S1), and a third end face (S3) and a fourth end face (S4) perpendicular to the first end face (S1). In the first prism (141), a first square prism-shaped protrusion (141a) having an end face that totally reflects the transmitted light is provided on a part of the second end face (S2), and a second square prism-shaped protrusion (141b) having an end face that totally reflects the transmitted light is provided on a part of the third end face (S3), The composite prism (120) is capable of generating the time-resolved pulsed laser light (L2) through partial reflection and partial transmission at the first partial reflective film (123a) and total reflection at the first rectangular prism-shaped protrusion (141a), the second rectangular prism-shaped protrusion (141b), and the fourth end face (S4). <2> The light source device described in (a device composed of 110 and 120). <13> The first prism (143) has a first end face (S1) to which the second prism (124) is fixed, a second end face (S2) parallel to the first end face (S1), and a third end face (S3) and a fourth end face (S4) perpendicular to the first end face (S1). In the first prism (143), a first rectangular prism-shaped protrusion (142a) having three end faces that cause total internal reflection of the transmitted light is provided on a part of the second end face (S2), the third end face (S3), or the fourth end face (S4), and a second rectangular prism-shaped protrusion (143a) having three end faces that cause total internal reflection of the transmitted light is provided on a part of the second end face (S2), the third end face (S3), or the fourth end face (S4), The composite prism (120) is capable of generating the time-resolved pulsed laser light (L2) through partial reflection and partial transmission at the first partial reflective film (123a), total reflection at the first rectangular prism-shaped protrusion (142a), total reflection at the second rectangular prism-shaped protrusion (143a), and total reflection at the end faces of the second end face (S2), third end face (S3), and fourth end face (S4) where the first rectangular prism-shaped protrusion (142a) and the second rectangular prism-shaped protrusion (143a) are not formed. <2> The light source device described in (a device composed of 110 and 120). <14> The first prism (142, 144) has a first end face (S1) to which the second prism (124) is fixed, a second end face (S2) parallel to the first end face (S1), and a third end face (S3) and a fourth end face (S4) perpendicular to the first end face (S1). In the first prism (142, 144), a first rectangular prism-shaped protrusion (142a) having three end faces that cause total internal reflection of the transmitted light is provided on a part of the second end face (S2), the third end face (S3), or the fourth end face (S4). The composite prism (120) is capable of generating the time-resolved pulsed laser light (L2) through partial reflection and partial transmission at the one or more partial reflective films (123a, 123e), total reflection at the first rectangular prism-shaped protrusion (141c), and total reflection at the end face among the second end face (S2), third end face (S3), and fourth end face (S4) where the first rectangular prism-shaped protrusion (142a) is not formed. <2> The light source device described in (a device composed of 110 and 120). <15> The pulsed laser light (L1) has a peak wavelength in the ultraviolet region. <1> or <14> A light source device described in any one of the items (a device composed of 110, 120). <16> The pulsed laser light (L1) is either unpolarized or circularly polarized light. The one or more partial reflective films (123a, 123d, 123e) have a film structure such that when the pulsed laser light (L1) is incident at an incident angle of 45°, the transmittance of the pulsed laser light (L1) is greater than the reflectance of the pulsed laser light (L1). <1> or <15> A light source device described in any one of the items (a device composed of 110, 120). <17> The pulsed laser light (L1) is linearly polarized light, The one or more partial reflective films (123a, 123d, 123e) have a film structure such that when the pulsed laser light (L1) is incident as p-polarized or s-polarized light at an incident angle of 45°, the transmittance of the pulsed laser light (L1) is greater than the reflectance of the pulsed laser light (L1). <1> or <15> A light source device described in any one of the items (a device composed of 110, 120). <18> A light source device (110, 120) capable of outputting inspection light (L2) to the object to be inspected (TG), A processing device (130) capable of inspecting the inspection target (TG) based on the reflected light (L4) or transmitted light (L3) from the inspection target (L2) of the inspection light (L2), and Equipped with, The light source device (110, 120) is the light source device (110, 120) described in any one of claims 1 to 17, and is capable of outputting the time-resolved pulsed laser light (L2) as the inspection light (L2) to the object to be inspected (TG). Inspection device (100). [Explanation of symbols]

[0174] 100...Inspection device, 110...Pulsed laser light source, 120...Time-division device, 130...Processing device, 121...Main prism, 122,124,125,126,127,128,129...Sub-prisms, 123a,123d,123e...Partial reflective film, 123b,123c...Anti-reflective film, 140...Prism, 141a,141b,142a,143a...Convex part, L1...Pulsed laser light, L2...Time-division pulsed laser light, L3,L11t,L12t,L13t,L14t,L15t,L16t,L17t,L18t,L19t ,L20t,L21t,L22t,L111t,L112t,L121t,L122t...Transmitted light, L4,L11r,L12r,L13r,L14r,L15r,L16r,L17r,L18r,L19r,L20r,L21r,L22r,L111r, L112r,L121r,L122r,L1111r,L1121r,L1211r,L1222r…Reflected light, 141,142,143,144…Prism, S1,S2,S3,S4,S5,S6,S7,S8,S9,S10…End face, TG…Inspection target.

Claims

1. A light source capable of outputting pulsed laser light, A composite prism in which multiple prisms and one or more partial reflective films are integrated. Equipped with, The composite prism divides the incident pulsed laser light in time within the composite prism by total internal reflection in the plurality of prisms and partial reflection and partial transmission in the one or more partial reflective films, thereby generating and outputting time-resolved pulsed laser light in which the pulsed light contained in the pulsed laser light is divided in time. Light source device.

2. The composite prism includes, as the plurality of prisms, a first prism and a second prism fixed to the first prism. The first partial reflective film in the one or more partial reflective films is provided between the first prism and the second prism, and is capable of splitting the pulsed laser light into transmitted light and reflected light. The light source device according to claim 1.

3. The first prism is a first rectangular prism having a first end face to which the second prism is fixed, a second end face parallel to the first end face, and third and fourth end faces perpendicular to the first end face. The composite prism is capable of generating the time-resolved pulsed laser light through partial reflection and partial transmission at the one or more partial reflective films, and total reflection at the second, third, and fourth end faces. The light source device according to claim 2.

4. The second prism is a right-angle prism, The right-angle prism has a fifth end face and a sixth end face that are perpendicular to each other, and a seventh end face connected to the fifth end face. The first partial reflective film is in contact with the first end face and the seventh end face. The fifth end face is the incident surface of the pulsed laser light, The sixth end face is the emission surface of the time-resolved pulsed laser light. The light source device according to claim 3.

5. The second prism is an isosceles trapezoidal prism, The isosceles trapezoidal prism has an eighth end face corresponding to the upper base of the trapezoid, a ninth end face corresponding to the lower base of the trapezoid, and tenth and eleventh end faces corresponding to the legs of the trapezoid, The first partial reflective film is in contact with the first end face and the ninth end face, The tenth end face is the incident surface of the pulsed laser light, The 11th end face is the emission surface of the time-resolved pulsed laser light. The light source device according to claim 3.

6. The composite prism includes, as the plurality of prisms, the first prism, the second prism, and one or more second rectangular prism-shaped prisms fixed to the first prism or the second prism and providing a time delay. The light source device according to claim 5.

7. The composite prism includes, as the plurality of second rectangular prism-shaped prisms, a third prism fixed to the second end face and having an end face that totally reflects the transmitted light, and a fourth prism fixed to the third end face and having an end face that totally reflects the transmitted light. The light source device according to claim 6.

8. The composite prism includes a fifth prism, which is fixed to the second, third, or fourth end face of the single second rectangular prism and has three end faces that cause total internal reflection of the transmitted light. The light source device according to claim 6.

9. The composite prism includes, as the plurality of second rectangular prism-shaped prisms, a fifth prism fixed to the second, third, or fourth end face and having three end faces that cause total internal reflection of the transmitted light, and a sixth prism fixed to the second, third, or fourth end face and having three end faces that cause total internal reflection of the transmitted light. The light source device according to claim 6.

10. The composite prism includes, as the plurality of second rectangular prism-shaped prisms, a seventh prism fixed to the eighth end face and having three end faces that cause total internal reflection of the transmitted light, and a fifth prism fixed to the second end face, the third end face, or the fourth end face and having three end faces that cause total internal reflection of the transmitted light. The second partial reflective film in the plurality of partial reflective films is provided between the second prism and the seventh prism, and is capable of splitting the pulsed laser light into transmitted light and reflected light. The light source device according to claim 6.

11. The composite prism includes, as the plurality of prisms, the first prism, the second prism, and a second rectangular prism fixed to the first prism and providing a time delay. The second partial reflective film in the plurality of partial reflective films is provided between the first prism and the second rectangular prism-shaped prism, and is capable of splitting the pulsed laser light into transmitted light and reflected light. The light source device according to claim 4.

12. The first prism has a first end face to which the second prism is fixed, a second end face parallel to the first end face, and a third and fourth end face perpendicular to the first end face. In the first prism, a first square prism-shaped protrusion having an end face that totally reflects the transmitted light is provided on a part of the second end face, and a second square prism-shaped protrusion having an end face that totally reflects the transmitted light is provided on a part of the third end face. The composite prism is capable of generating the time-resolved pulsed laser light through partial reflection and partial transmission at the first partial reflective film, and total reflection at the first rectangular prism-shaped protrusion, the second rectangular prism-shaped protrusion, and the fourth end face. The light source device according to claim 2.

13. The first prism has a first end face to which the second prism is fixed, a second end face parallel to the first end face, and a third and fourth end face perpendicular to the first end face. In the first prism, a first quadrangular prism-shaped protrusion having three end faces that cause total internal reflection of the transmitted light is provided on the second end face, the third end face, or a part of the fourth end face, and a second quadrangular prism-shaped protrusion having three end faces that cause total internal reflection of the transmitted light is provided on the second end face, the third end face, or a part of the fourth end face, The composite prism is capable of generating the time-resolved pulsed laser light through partial reflection and partial transmission at the first partial reflective film, total reflection at the first rectangular prism-shaped protrusion, total reflection at the second rectangular prism-shaped protrusion, and total reflection at the end faces of the second, third, and fourth end faces where the first and second rectangular prism-shaped protrusions are not formed. The light source device according to claim 2.

14. The first prism has a first end face to which the second prism is fixed, a second end face parallel to the first end face, and a third and fourth end face perpendicular to the first end face. In the first prism, a first rectangular prism-shaped protrusion is provided on the second end face, the third end face, or a part of the fourth end face, having three end faces that cause total internal reflection of the transmitted light. The composite prism is capable of generating the time-resolved pulsed laser light through partial reflection and partial transmission at the one or more partial reflective films, total reflection at the first rectangular prism-shaped protrusion, and total reflection at the end faces of the second, third, and fourth end faces where the first rectangular prism-shaped protrusion is not formed. The light source device according to claim 2.

15. The pulsed laser light has a peak wavelength in the ultraviolet region. A light source device according to any one of claims 1 to 14.

16. The pulsed laser light is either unpolarized or circularly polarized light. The one or more partial reflective films have a film structure in which the transmittance of the pulsed laser light is greater than the reflectance of the pulsed laser light when the pulsed laser light is incident at an incident angle of 45°. A light source device according to any one of claims 1 to 14.

17. The pulsed laser light is linearly polarized light, The one or more partial reflective films have a film structure such that when the pulsed laser light is incident as p-polarized or s-polarized light at an incident angle of 45°, the transmittance of the pulsed laser light is greater than the reflectance of the pulsed laser light. A light source device according to any one of claims 1 to 14.

18. A light source device capable of outputting inspection light to the object to be inspected, A processing apparatus capable of inspecting the object to be inspected based on the reflected light from the object to be inspected or the transmitted light from the object to be inspected, among the inspection light, Equipped with, The light source device is the light source device described in any one of claims 1 to 17, and is capable of outputting the time-resolved pulsed laser light as the inspection light to the object to be inspected. Inspection equipment.

Images