Laser generating device with wavelength of 215-222nm

Abstract

This invention relates to a laser generating device with a wavelength of 215-222 nm, comprising: an excitation light source unit that converts laser light with a wavelength of 1030-1064 nm into a second harmonic to generate laser light with a wavelength of 515-532 nm; an optical parametric oscillation unit that uses the laser light with a wavelength of 515-532 nm as excitation light to generate signal light with a wavelength of 858-887 nm and idle light with a wavelength of 1288-1330 nm; a separation unit that separates the signal light and the idle light; a first wavelength conversion unit that generates a fourth harmonic from the signal light; a second wavelength conversion unit that generates deep ultraviolet light with a wavelength of 215-222 nm from the idle light by light summing with the second harmonic of the excitation light; and a coupling unit that couples the fourth harmonic from the first wavelength conversion unit with the deep ultraviolet light from the second wavelength conversion unit. This invention provides a laser generating device capable of efficiently and simply generating pulsed laser light with a wavelength of 215-222 nm, including a wavelength of 222 nm that inactivates microorganisms.

Description

Technical Field

[0001] This invention relates to a laser generating device with a wavelength of 215–222 nm. More specifically, this invention relates to an all-solid-state wavelength conversion laser generating device that efficiently generates deep ultraviolet lasers with wavelengths of 215–222 nm that do not affect the human body and have bactericidal effects (including virus inactivation, hereinafter the same).

[0002] Cross-references to related applications

[0003] This application claims priority to Japanese Patent Application No. 2021-027496, filed on February 24, 2021, the entire contents of which are hereby incorporated as public information. Background Technology

[0004] Deep ultraviolet radiation has been used since ancient times as a means of inactivating microorganisms such as bacteria and viruses. This is because deep ultraviolet light can induce photochemical reactions such as hydration, dimer formation, and decomposition within DNA, thereby disrupting the helical structure of DNA, forming cyclobutanepyrimidines, and killing bacterial cells.

[0005] Considering its impact on the human body, deep ultraviolet light has traditionally been avoided for human use. However, while deep ultraviolet light with a wavelength of 222nm has almost the same bactericidal effect as, or even higher depending on the type of bacteria, it has attracted attention because it is absorbed by the stratum corneum of human skin. Therefore, it has less impact on the human body compared to traditional ultraviolet light.

[0006] UV lamps, such as KrCl lamps, are known sources of light with a wavelength of 222 nm. However, the emission spectrum of UV lamps also includes deep ultraviolet light with wavelengths beyond 222 nm that are harmful to the human body, thus requiring filters to block this light (e.g., Patent Documents 1, 2, and 3). Therefore, highly efficient sterilization effects cannot be achieved. Furthermore, regarding light-emitting diodes (LEDs), which have attracted attention as alternative light sources to mercury lamps, only microwatt-level outputs are currently possible below wavelengths of 265 nm.

[0007] Generally, lasers have a narrower spectrum compared to UV lamps. A laser source that oscillates only deep ultraviolet light around 222nm, a wavelength conducive to sterilization, would be extremely useful. Due to the good directivity of lasers, energy can be concentrated on a narrow area, allowing more deep ultraviolet light to reach the DNA inside the cell wall or cell membrane of microorganisms, potentially resulting in a short-term sterilization effect. In recent years, semiconductor lasers have attracted attention as an alternative light source to mercury lamps. However, high-output oscillations below 270nm have not been reported, and laser sources oscillating only deep ultraviolet light around 222nm are unknown.

[0008] As a source of deep ultraviolet laser light, KrF laser devices are known, but their oscillation wavelength is 248 nm. Alternatively, deep ultraviolet light with a wavelength of 266 nm is also known, generated by the fourth harmonic of an Nd:YAG laser oscillating at a wavelength of 1064 nm, but not 222 nm. Furthermore, these wavelengths are deep ultraviolet light that can affect the human body.

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-220684

[0010] Patent Document 2: Japanese Patent Application Publication No. 2017-136145

[0011] Patent Document 3: Japanese Patent Application Publication No. 2018-114197

[0012] Patent Document 4: Japanese Patent Application Publication No. 2007-86101

[0013] Patent Document 5: Japanese Patent Application Publication No. 2003-5233

[0014] Patent Document 6: Japanese Patent Application Publication No. 2003-280055

[0015] All the contents of Patent Documents 1 to 6 are hereby introduced as public information. Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] Therefore, there is a need for a laser generating device that uses existing laser light sources and can efficiently utilize the light from the light source at a wavelength of 222 nm, and in particular, there is a desire for a laser generating device at a wavelength of 222 nm based on an all-solid-state system using nonlinear optical elements.

[0018] As a deep ultraviolet light source that efficiently generates deep ultraviolet light with a wavelength of 222nm, a small and well-maintainable all-solid-state laser is required, but sufficient performance has not been achieved in previous devices that used semiconductor lasers or excimer lasers.

[0019] For example, Patent Document 4 discloses a laser device that uses two semiconductor laser sources to generate laser light in the deep ultraviolet region with wavelengths of 190–270 nm. In this device, a 227 nm laser is obtained using nonlinear optical elements, but the generation of a 222 nm laser is not described.

[0020] Patent Document 5 describes a deep ultraviolet laser generating device using a semiconductor laser source and nonlinear optical elements, while Patent Document 6 describes a deep ultraviolet laser generating device using a semiconductor laser source, nonlinear optical elements, and an optical parametric oscillator. However, the target ultraviolet wavelength of the device described in Patent Document 5 is different; it is the fifth harmonic of the output light from a 788.145 nm Ti:sapphire laser generated based on a KBBF crystal. It is not a laser generating device with a wavelength of 222 nm.

[0021] The target ultraviolet wavelength of the device described in Patent Document 6 is also different; it is not a laser generating device with a wavelength of 222 nm. Furthermore, although it uses the output light of the second harmonic excitation optical parametric oscillation from an Nd:YAG laser, it does not use the idle light from the optical parametric oscillation, which differs from the present invention.

[0022] The present invention was made in view of the above background, and its object is to provide a laser generating device based on an all-solid-state system, which efficiently generates lasers with wavelengths of 215 to 222 nm, including wavelengths of 222 nm, that have no effect on the human body and have a bactericidal effect, such as pulsed lasers.

[0023] Methods for solving problems

[0024] The present invention is described below.

[0025] [1] A laser generating device with a wavelength of 215-222nm, comprising:

[0026] The excitation light source unit converts laser light with a wavelength of 1030-1064nm into a second harmonic to generate laser light with a wavelength of 515-532nm.

[0027] The optical parametric oscillation section uses a laser with a wavelength of 515–532 nm generated by the excitation source section as the excitation light to generate signal light with a wavelength of 858–887 nm and idle light with a wavelength of 1288–1330 nm.

[0028] The separation unit separates the signal light with a wavelength of 858–887 nm from the idle light with a wavelength of 1288–1330 nm.

[0029] The first wavelength conversion unit generates a fourth harmonic with a wavelength of 215-222nm from signal light with a wavelength of 858-887nm;

[0030] The second wavelength conversion section generates deep ultraviolet light with a wavelength of 215-222 nm by combining idle light with light of 258-266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1288-1330 nm; and

[0031] The coupling section couples the fourth harmonic wavelength (215–222 nm) from the first wavelength conversion section with the deep ultraviolet light (215–222 nm) from the second wavelength conversion section.

[0032] [2] A laser generating apparatus according to [1], which is a 222nm wavelength laser generating apparatus, comprising:

[0033] The excitation light source converts the 1064nm wavelength laser into a second harmonic, generating a 532nm wavelength laser.

[0034] The optical parametric oscillation unit uses a 532nm wavelength laser generated by the excitation source unit as the excitation light to produce a signal light with a wavelength of 887nm and an idle light with a wavelength of 1330nm.

[0035] The separation unit separates the signal light with a wavelength of 887nm from the idle light with a wavelength of 1330nm;

[0036] The first wavelength conversion unit generates a fourth harmonic with a wavelength of 222nm from a signal light with a wavelength of 887nm.

[0037] The second wavelength conversion unit generates deep ultraviolet light with a wavelength of 222 nm by combining idle light with light of 266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1330 nm; and

[0038] The coupling section couples the fourth harmonic of wavelength 222nm from the first wavelength conversion section with the deep ultraviolet light of wavelength 222nm from the second wavelength conversion section.

[0039] [3] According to the laser generating device described in [1] or [2], wherein,

[0040] It also includes an Nd:YAG laser oscillation device that generates laser light with wavelengths of 1030–1064 nm.

[0041] [4] The laser generating apparatus according to any one of [1] to [3], wherein,

[0042] The excitation light source section includes a nonlinear optical crystal that converts laser light with a wavelength of 1030–1064 nm into a second harmonic.

[0043] [5] The laser generating apparatus according to any one of [1] to [4], wherein,

[0044] The optical parametric oscillator is an optical parametric oscillator device that includes a nonlinear optical crystal and two mirrors.

[0045] [6] The laser generating apparatus according to any one of [1] to [5], wherein,

[0046] The first wavelength conversion section contains two or more nonlinear optical crystals.

[0047] [7] The laser generating apparatus according to any one of [1] to [6], wherein,

[0048] The second wavelength conversion section contains two or more nonlinear optical crystals.

[0049] [8] The laser generating apparatus according to any one of [1] to [7], wherein,

[0050] It also includes a dichroic mirror that reflects light with wavelengths of 1030–1064 nm from the excitation source between the excitation source and the optical parametric oscillation section, thereby obtaining laser light with wavelengths of 515–532 nm.

[0051] [9] The laser generating apparatus according to any one of [1] to [8], wherein,

[0052] The rear part of the coupling section also has a prism that separates light wavelengths other than 215-222nm.

[0053]

[10] The laser generating apparatus according to any one of [1] to [9], wherein,

[0054] Lasers with wavelengths of 1030–1064 nm are pulsed lasers, and the pulse duration is either nanoseconds or picoseconds.

[0055] The effects of the invention

[0056] According to the present invention, the following effects can be achieved: a laser generating device with excellent operability is provided that can efficiently and easily generate lasers (e.g., pulsed lasers) in the wavelength range of 215 to 222 nm, including 222 nm for sterilization.

[0057] By using the aforementioned laser device for sterilization, sterilization can be effectively performed in a short time while avoiding any impact on the human body. Regarding the laser generating device involved in this embodiment, since all necessary components are designed as solid-state systems, it is also a device that requires virtually no maintenance. Attached Figure Description

[0058] Figure 1 A schematic diagram illustrating the laser generating apparatus of the present invention is shown.

[0059] Figure 2 A schematic diagram illustrating one embodiment of the laser generating apparatus of the present invention is shown.

[0060] Figure 3 An embodiment of the laser generating apparatus of the present invention is shown.

[0061] Figure 4 The diagram illustrates that the wavelength of the fourth harmonic of the OPO signal light λs coincides with the wavelength of the light sum frequency generated by the OPO idle light λi and the second harmonic of the 532nm light used as excitation light, i.e., the 266nm light, at 222nm. Detailed Implementation

[0062] The laser generating device with a wavelength of 215-222nm of the present invention comprises:

[0063] The excitation light source unit converts laser light with a wavelength of 1030-1064nm into a second harmonic to generate laser light with a wavelength of 515-532nm.

[0064] The optical parametric oscillation section uses a laser with a wavelength of 515–532 nm generated by the excitation source section as the excitation light to generate signal light with a wavelength of 858–887 nm and idle light with a wavelength of 1288–1330 nm.

[0065] The separation unit separates the signal light with a wavelength of 858–887 nm from the idle light with a wavelength of 1288–1330 nm.

[0066] The first wavelength conversion unit generates a fourth harmonic with a wavelength of 215-222nm from signal light with a wavelength of 858-887nm;

[0067] The second wavelength conversion section generates deep ultraviolet light with a wavelength of 215-222 nm by combining idle light with light of 258-266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1288-1330 nm; and

[0068] The coupling section couples the fourth harmonic wavelength (215–222 nm) from the first wavelength conversion section with the deep ultraviolet light (215–222 nm) from the second wavelength conversion section.

[0069] As one embodiment of the laser generating apparatus of the present invention, a 222nm wavelength laser generating apparatus includes:

[0070] The excitation light source converts the 1064nm wavelength laser into a second harmonic, generating a 532nm wavelength laser.

[0071] The optical parametric oscillation unit uses a 532nm wavelength laser generated by the excitation source unit as the excitation light to produce a signal light with a wavelength of 887nm and an idle light with a wavelength of 1330nm.

[0072] The separation unit separates the signal light with a wavelength of 887nm from the idle light with a wavelength of 1330nm;

[0073] The first wavelength conversion unit generates a fourth harmonic with a wavelength of 222nm from a signal light with a wavelength of 887nm.

[0074] The second wavelength conversion unit generates deep ultraviolet light with a wavelength of 222 nm by combining idle light with light of 266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1330 nm; and

[0075] The coupling section couples the fourth harmonic of wavelength 222nm from the first wavelength conversion section with the deep ultraviolet light of wavelength 222nm from the second wavelength conversion section.

[0076] Figure 1 A schematic diagram illustrating the laser generating apparatus of the present invention is shown below, taking a 222nm wavelength laser generating apparatus as an example.

[0077] 10 is the excitation light source section, 20 is the optical parametric oscillation section, 30 is the separation section, 40 is the first wavelength conversion section, 50 is the second wavelength conversion section, and 60 is the coupling section.

[0078] Figure 2 This is a schematic diagram illustrating an example of a 222nm wavelength laser generating apparatus as one embodiment of the laser generating apparatus of the present invention, particularly showing the case where the first wavelength conversion unit 40 includes SHG 40a and SHG 40b, and the second wavelength conversion unit 50 includes SHG 50a and SFG 50b.

[0079] Figure 3 The diagram shows an example of a 222nm wavelength laser generating apparatus as one embodiment of the laser generating apparatus of the present invention.

[0080] In addition, the abbreviations used in this application have the following meanings.

[0081] SHG: Second Harmonic Generation

[0082] 4HG: Fourth Harmonic Generation

[0083] SFG: Sum Frequency Generation

[0084] OPO: Optical Parametric Oscillator

[0085] KTP: KTiOPO4

[0086] BBO: β-BaB2O4

[0087] LBO:LiB3O5

[0088] RTP: RbTiOPO4

[0089] KTA: KTiOAsO4

[0090] MgO:PPLT: Periodically Poled LiTaO3 with MgO

[0091] KBBF: KBe2BO3F2

[0092] The laser generating device of the present invention will be described below using a 222nm wavelength laser generating device as an example.

[0093] (Explanation of the excitation light source section)

[0094] The excitation source unit 10 is a section that converts a 1064nm wavelength laser into a second harmonic to generate a 532nm wavelength laser. The excitation source for generating the 1064nm wavelength laser can be, for example, Nd:YAG(Nd...) 3+ :Y3Al5O 12 Lasers. Lasers with a wavelength of 1064 nm are pulsed lasers, and the pulse duration can be nanoseconds or picoseconds. As a source that oscillates to produce lasers with wavelengths from 1030 to 1064 nm, besides Nd:YAG (Nd... 3+ :Y3Al5O 12 Besides lasers, other examples include Nd:YVO4 with a wavelength of 1064 nm, Nd:YLF (LiYF4) with wavelengths of 1053 nm and 1047 nm, Yb:YAG with a wavelength of 1030 nm, and Nd:GdVO4 with a wavelength of 1063 nm. Since the wavelength conversion of these laser sources utilizes a second-order nonlinear optical effect, they are essentially pulsed light sources that generate strong electric fields. However, if resonators are used in conjunction with each process, continuous light wavelength conversion can also be achieved.

[0095] The excitation source unit 10 may include, for example, an excitation source and a nonlinear optical crystal that converts its laser light into a 532nm laser as a second harmonic. The nonlinear optical crystal may, for example, be a KTP crystal. Figure 3 The image shows crystal 1. Besides KTP crystal, crystal 1 can also be any of BBO, LBO, MgO:PPLT, or PPKTP. Additionally, "PP + crystal name" stands for "Periodically Poled".

[0096] More specifically, in the case of using KTP crystals in nonlinear optical crystals, such as Figure 3As shown, the laser light from the excitation source is passed through a half-wave plate (λ / 2 plate) and its polarization direction is tilted at 45 degrees before passing through crystal 1, converting it into a 532nm laser as a second harmonic. The phase matching in the wavelength conversion is type 2. Furthermore, when crystal 1 uses an LBO or BBO crystal, the polarization direction is made perpendicular to the plane of the paper after passing through the λ / 2 plate, and then the light is converted into a 532nm laser as a second harmonic. Further, when crystal 1 uses MgO:PPLT or PPKTP, the λ / 2 plate is not needed. Crystal 1 is set so that the polarization direction of the 532nm laser is horizontal to the plane of the paper. Additionally, type 2 phase matching means that the second harmonic is generated from incident light of different rays (i.e., orthogonally polarized different rays), which is different from type 1 phase matching where the second harmonic is generated from incident light of the same ray (i.e., with the same polarization). Further, in this specification, phase matching where the direction of the incident light and the second harmonic are both the same (abnormal ray) is referred to as type 0.

[0097] Table 1 below lists the types of crystals that can be used in the excitation light source section, the optical parametric oscillation section, the first wavelength conversion section, and the second wavelength conversion section, along with their functions, phase matching types, and polarization characteristics. Table 1 uses a light source wavelength of 1064 nm as an example, but for light source wavelengths in the range of 1030–1064 nm, the usable crystals listed for crystals 1–6 have the functions, phase matching types, and polarization characteristics described in Table 1.

[0098] [Table 1]

[0099]

[0100] In Table 1, "o" in the polarization column refers to ordinary wave, and "e" refers to extraordinary wave.

[0101] (Dialect mirror M1)

[0102] A dichroic mirror can be installed between the excitation light source section 10 and the OPO 20. Figure 3 The dichroic mirror M1 reflects the 1064nm light contained in the light from the excitation source 10 to obtain a 532nm laser. Since the 1064nm light is not used in subsequent processes, separating it from the 532nm laser first avoids unnecessary damage to optical components or temperature load on the crystal when focusing other wavelengths of laser light in subsequent processes. The 532nm laser light transmitted through the dichroic mirror M1 is then incident on the OPO.

[0103] (Explanation of the Optical Parametric Oscillator (OPO))

[0104] OPO 20 is a section that uses a 532nm wavelength laser generated by the excitation source as the excitation light to produce an 887nm wavelength signal light and a 1330nm wavelength idler light, and separates the generated signal light. OPO includes a nonlinear optical crystal and two mirrors. The nonlinear optical crystal can be, for example, a KTP crystal or a similar crystal. Figure 3 Crystal 2 is shown in the diagram. Similar crystals to KTP crystals include RTP and KTA crystals, as well as BBO, MgO:PPLT, or PPKTP. Crystal 2 is cut to produce a phase-matching angle that generates a signal light λs with a wavelength of 887 nm and an idle light λi with a wavelength of 1330 nm. Furthermore, MgO:PPLT and PPKTP are adjusted to have a polarization reversal period length capable of generating the aforementioned signal and idle light wavelengths. The two wavelengths emitted from this crystal are amplified by a resonator containing two mirrors to obtain OPO oscillation. When crystal 2 constituting the optical parametric oscillator 20 is a similar crystal to KTP crystals, since the phase matching is type 2, the excitation light and idle light are polarized horizontally with respect to the paper surface, while the signal light is polarized in a direction perpendicular to the paper surface. When crystal 2 constituting the optical parametric oscillator 20 is a BBO crystal with type 1 phase matching, if the excitation light is polarized horizontally with respect to the paper surface, the signal light and idle light are polarized in a direction perpendicular to the paper surface. When the crystal 2 constituting the optical parametric oscillator 20 is set as an MgO:PPLT or PPKTP crystal, since it is a process with phase matching of type 0, the excitation light, signal light and idle light are polarized in the direction horizontal to the paper plane.

[0105] (Separation section 30)

[0106] A separation section 30 is provided between the OPO and the first and second wavelength conversion sections. This separation section 30 separates the signal light with a wavelength of 887 nm from the idle light with a wavelength of 1330 nm. Considering subsequent processes, the separation section 30 preferably allows the idle light of 1330 nm and the unconverted excitation light of 532 nm to pass through. The separation section 30 can be, for example, a dichroic mirror (…). Figure 3 (M2 in the diagram). At dichroic mirror M2, only the 887nm signal light from the OPO-converted signal light and the idle light is reflected, while the 1330nm idle light and the unconverted 532nm excitation light are transmitted. When the polarization directions of the signal light and the idle light are different (type 2 phase matching), a polarizer can be used as the separation unit 30. In this case, horizontally polarized light passes through the polarizer, and vertically polarized light is reflected.

[0107] (First wavelength conversion unit 40)

[0108] The first wavelength conversion unit 40 converts the signal light with a wavelength of 887nm to the 4HG section with a wavelength of 222nm. Specifically, as follows: Figure 2 As shown, it may include SHG 40a, which converts 887nm signal light into 444nm blue light, and SHG 40b, which converts 444nm light into 222nm deep ultraviolet light.

[0109] With the dichroic mirror M2 in the separation section 30, the SHG 40a converts the reflected 887nm signal light into 444nm blue light. The SHG 40a can be, for example, a nonlinear optical crystal such as an LBO or BBO crystal. Figure 3 Crystal 3 is shown in the diagram. This crystal 3 is cut to match the 887nm fundamental type 1 phase to the 444nm SHG at an angle. The polarization direction of the 444nm light is horizontal. When the crystal 2 constituting the optical parametric oscillator 20 is a MgO:PPLT or PPKTP crystal, the SHG40a is a MgO:PPLT crystal with a polarization reversal period length that generates an 888nm SHG. In this case, the polarization direction of the 444nm light is also horizontal to the plane of the paper.

[0110] SHG 40b converts 444nm light into 222nm deep ultraviolet light, and can be, for example, a nonlinear optical crystal such as BBO. Figure 3 In the diagram, crystal 4 is shown. 444nm light is incident on the BBO of crystal 4 and further converted by SHG, thereby obtaining deep ultraviolet light with a wavelength of 222nm. Besides BBO, crystal 4 can also be a nonlinear optical crystal such as KBBF, to cut the fundamental wave propagating at an angle matching the type 1 phase of the 444nm fundamental wave to the SHG of the 222nm wavelength, or to be held by a quartz prism. The polarization direction of the 222nm light is perpendicular to the plane of the paper. The generated 222nm light is combined with the 222nm light generated on the other side at the coupling part 60.

[0111] The first wavelength conversion unit 40 may include two or more crystals. When each of SHG 40a and SHG 40b includes one crystal, the first wavelength conversion unit 40 includes two crystals. SHG 40a and SHG 40b may also each be a device composed of two crystals of the same length and cut angle arranged in series, thereby improving conversion efficiency. In this case, the first wavelength conversion unit 40 may include three or more crystals.

[0112] (Second wavelength conversion unit 50)

[0113] The second wavelength conversion unit 50 is a section that generates deep ultraviolet light with a wavelength of 222nm by combining the idle light with a wavelength of 1330nm separated by the separation unit 30 with the second harmonic of 266nm light used as excitation light. Figure 2 As shown, the second wavelength conversion unit includes converting excitation light with a wavelength of 532 nm into SHG 50a with a wavelength of 266 nm, and re-intruding deep ultraviolet light with a wavelength of 266 nm and idle light with a wavelength of 1330 nm generated from OPO and generating SFG50b with a wavelength of 222 nm through light and frequency mixing.

[0114] SHG 50a can be, for example, a nonlinear optical crystal such as BBO or CLBO, in Figure 3 Crystal 5 is shown in the diagram. The excitation light with a wavelength of 532 nm, which has passed through the dichroic mirror M2 (serving as the separation section 30) and the idle light, is incident on crystal 5 and converted to a wavelength of 266 nm by a SHG. Crystal 5 is cut at an angle such that the fundamental type 1 phase of the 532 nm wavelength is matched to the SHG of the 266 nm wavelength. The polarization direction of the 266 nm light is perpendicular to the horizontal direction.

[0115] SFG 50b, for example, can use nonlinear optical crystals such as CLBO crystals, in... Figure 3 Crystal 6 is shown in the diagram. Deep ultraviolet light with a wavelength of 266 nm, obtained by conversion using crystal 5, and idle light with a wavelength of 1330 nm generated from the OPO are incident on crystal 6 again, generating 222 nm light through light and frequency mixing. Crystal 6 can be a nonlinear optical crystal such as a BBO, in addition to a CLBO, and is cut into two types of phase-matched crystals. The polarization direction of the generated 222 nm light is horizontal. When crystal 2, which constitutes the optical parametric oscillator 20, is set as a BBO with a type of phase matching, crystal 6 is cut into a type of phase-matched crystal.

[0116] The second wavelength conversion unit 50 may contain two or more crystals. If each of the SHG 50a and SFG 50b contains one crystal, the second wavelength conversion unit 50 contains two crystals. Alternatively, each of the SHG 50a and SFG 50b may be a device composed of two crystals of the same length and cut angle arranged in series, thereby improving conversion efficiency. In this case, the second wavelength conversion unit 50 may contain three or more crystals.

[0117] (Coupled section 60)

[0118] The coupling section 60 is combined with the first wavelength conversion section 40. Figure 2 The 222nm light generated by the SHG 40b and the second wavelength conversion section 50 ( Figure 2 The SFG 50b) generates 222nm light. The coupling part 60 can be, for example, a polarizer.

[0119] A separation section 70 can be provided at the rear of the coupling section 60. Figure 1 and Figure 2 (Not shown in the figure), the separation unit 70 is used to separate laser light of various wavelengths generated during wavelength conversion and extract 222nm light. The separation unit 70 can be, for example, a prism (see Figure 1). Figure 3 There are no particular restrictions as long as the laser light with wavelengths other than 222nm generated during the wavelength conversion process can be removed; for example, it can be a quartz prism, MgF2 prism, etc. The separation unit 70 separates the light with wavelengths other than 222nm to obtain a laser light with a wavelength of 222nm.

[0120] Figure 3 The example shown is for the case where the optical parametric oscillator is of type 2. Examples of combinations of crystals 2-6 in the cases of type 0 and type 1 are compared with... Figure 3 The two types of cases shown are illustrated together in Table 2 below. However, these examples are merely illustrative, and the present invention is not intended to be limited to these examples. In addition, the examples of combinations of crystals 2 to 6 described in Table 2 are based on the case where the light source wavelength is 1064 nm, but when the light source wavelength is in the range of 1030 to 1064 nm, the same combinations of crystals 2 to 6 described in Table 2 can be used.

[0121] [Table 2]

[0122]

[0123] (Mechanism for generating laser light with wavelengths of 215–222 nm)

[0124] The mechanism for generating laser light with wavelengths of 215 to 222 nm in the device of the present invention will be described below using 222 nm as an example.

[0125] In an optical parametric oscillator (OPO), when the excitation wavelength is λp, the signal wavelength is λs, and the idle wavelength is λi, the following relationship exists.

[0126] (Equation 1) 1 / λs + 1 / λi = 1 / λp

[0127] In addition, when the incident light wavelength is λ1, another incident light wavelength is λ2, and the light sum frequency wavelength is λ3, the SFG exhibits the following relationship.

[0128] (Equation 2) 1 / λ1 + 1 / λ2 = 1 / λ3

[0129] In wavelength-conversion-based ultraviolet laser generation methods, various combinations of (Equation 1) and (Equation 2) are used to generate coherent light of the desired wavelength through the aforementioned relationship. Typically, deep ultraviolet lasers are generated by using the output light of either the signal light or the idle light in (Equation 1) for wavelength conversion, while the output light of the other light is not used but is cut off by a filter. Therefore, there is a disadvantage of low conversion efficiency to deep ultraviolet light for the entire system.

[0130] In this invention, as described above, an 887nm signal light λs and a 1330nm idle light λi are generated by an OPO excited by the second harmonic of a 1064nm laser, i.e., 532nm. Figure 4 As shown, the following characteristic is utilized: the wavelength of the fourth harmonic generated from the 887nm signal light λs at the first wavelength conversion section, which is 222nm, coincides with the wavelength of the light generated by the sum of frequencies from the idle light λi (1330nm) and the excitation light (532nm), which is 266nm, at the subsequent second wavelength conversion section. This mechanism functions identically when using a laser source in the wavelength range of 1030–1064nm to generate deep ultraviolet light in the wavelength range of 215–222nm.

[0131] In this invention, the output light from both the signal light and idle light of the OPO can be used to generate deep ultraviolet light with a wavelength of 215–222 nm. Therefore, a more efficient deep ultraviolet laser generating device with a wavelength of 215–222 nm can be realized.

[0132] The 222nm wavelength laser generated in the apparatus of the present invention may vary depending on the specifications of each component and operating conditions, but the wavelength is generally in the range of 221.5 to 222.1nm. Similarly, for lasers with wavelengths other than 222nm, the wavelength has a width that converges to approximately ±0.5nm, depending on the specifications of each component and operating conditions.

[0133] Since the 222nm wavelength laser obtained by the device of the present invention is only deep ultraviolet light with a wavelength of 222nm that is conducive to sterilization, unlike the case where a KrCl lamp with a wider spectral width is used as the light source, there is no need for a bandpass filter to block the excess deep ultraviolet light that may affect the human body.

[0134] The laser generating apparatus of the present invention can also be configured to have a relatively high output, so it can irradiate a wide area with deep ultraviolet light with a wavelength of 222 nm or irradiate liquids such as water, which is useful for applications such as entrances and exits of facilities with unspecified access and for the sterilization of liquids. Furthermore, the generated laser can be directed to a target object via a laser conductor such as an optical fiber, as needed. Therefore, for example, ultraviolet irradiation of parts such as the back side of a structure becomes easy.

[0135] Industrial availability

[0136] This invention is effective not only in medical settings but also in disinfection operations at large facilities. Furthermore, it has minimal impact on human health because it does not use toxic gases such as ozone or ethylene oxide, making it easy to manage and handle. Additionally, since it does not use liquid disinfectants such as alcohol, it can also be used for disinfecting paper media that cannot be wetted, such as books.

[0137] Label Explanation

[0138] 10 Excitation Light Source Section

[0139] 20 Optical Parametric Oscillation Section

[0140] 30 Separation Section

[0141] 40 First Wavelength Conversion Section

[0142] 50 Second Wavelength Conversion Section

[0143] 60 Coupling section

Claims

1. A laser generating device with a wavelength of 215-222 nm, comprising: The excitation light source unit converts laser light with a wavelength of 1030-1064nm into a second harmonic to generate laser light with a wavelength of 515-532nm. The optical parametric oscillation section uses a laser with a wavelength of 515–532 nm generated by the excitation source section as the excitation light to generate signal light with a wavelength of 858–887 nm and idle light with a wavelength of 1288–1330 nm. The separation unit separates the signal light with a wavelength of 858–887 nm from the idle light with a wavelength of 1288–1330 nm. The first wavelength conversion unit generates a fourth harmonic with a wavelength of 215-222nm from signal light with a wavelength of 858-887nm; The second wavelength conversion section generates deep ultraviolet light with a wavelength of 215-222 nm by combining idle light with light of 258-266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1288-1330 nm; and The coupling section couples laser light with a wavelength of 215–222 nm from the first wavelength conversion section with deep ultraviolet light with a wavelength of 215–222 nm from the second wavelength conversion section.

2. The laser generating device according to claim 1, wherein it is a 222nm wavelength laser generating device, comprising: The excitation light source converts the 1064nm wavelength laser into a second harmonic, generating a 532nm wavelength laser. The optical parametric oscillation unit uses a 532nm wavelength laser generated by the excitation source unit as the excitation light to produce a signal light with a wavelength of 887nm and an idle light with a wavelength of 1330nm. The separation unit separates the signal light with a wavelength of 887nm from the idle light with a wavelength of 1330nm; The first wavelength conversion unit generates a fourth harmonic with a wavelength of 222nm from a signal light with a wavelength of 887nm. The second wavelength conversion unit generates deep ultraviolet light with a wavelength of 222 nm by combining idle light with light of 266 nm, which is the second harmonic of the excitation light, from idle light with a wavelength of 1330 nm; and The coupling unit couples a 222nm wavelength laser light from the first wavelength conversion unit with a 222nm wavelength deep ultraviolet light light from the second wavelength conversion unit.

3. The laser generating apparatus according to claim 1 or 2, wherein, It also includes an Nd:YAG laser oscillation device that generates laser light with wavelengths of 1030–1064 nm.

4. The laser generating apparatus according to claim 1 or 2, wherein, The excitation light source section includes a nonlinear optical crystal that converts laser light with a wavelength of 1030–1064 nm into a second harmonic.

5. The laser generating apparatus according to claim 1 or 2, wherein, The optical parametric oscillator is an optical parametric oscillator device that includes a nonlinear optical crystal and two mirrors.

6. The laser generating apparatus according to claim 1 or 2, wherein, The first wavelength conversion section contains two or more nonlinear optical crystals.

7. The laser generating apparatus according to claim 1 or 2, wherein, The second wavelength conversion section contains two or more nonlinear optical crystals.

8. The laser generating apparatus according to claim 1 or 2, wherein, It also includes a dichroic mirror, which reflects light with wavelengths of 1030 to 1064 nm from the excitation light source between the excitation light source and the optical parametric oscillation section to obtain laser light with wavelengths of 515 to 532 nm.

9. The laser generating apparatus according to claim 1 or 2, wherein, The rear part of the coupling section also has a prism that separates light wavelengths other than 215-222nm.

10. The laser generating apparatus according to claim 1 or 2, wherein, Lasers with wavelengths of 1030–1064 nm are pulsed lasers, and the pulse duration is either nanoseconds or picoseconds.

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