Optical resonator, optical resonator component, and laser device

Abstract

[Problem] To provide an optical resonator, a constituent of an optical resonator, and a laser device that can be downsized even when a wavelength band limiting element is provided in the optical resonator. [Solution] An optical resonator includes: a laser medium arranged between a pair of reflecting members and emitting emission light excited by predetermined excitation light; and a wavelength band limiting element arranged on an emission side of the emission light between the pair of reflecting members, the wavelength band limiting element including two reflecting planes orthogonal to an optical axis of the laser medium and limiting a wavelength band of the emission light. The wavelength band limiting element is provided at a position that prevents a reflection member on a laser beam emission side in the pair of reflecting members from generating a resonant component outside an intended wavelength range of the wavelength band limiting element.

Description

Technical Field

[0001] This disclosure relates to optical resonators, components of optical resonators, and laser devices. Background Technology

[0002] In recent years, various laser devices have been developed. For example, passive Q-switched pulsed laser devices, which use passive elements to change the Q value, have been actively developed. The size of such laser devices has been reduced.

[0003] Furthermore, etalon elements are used as wavelength band limiting elements to narrow the laser beam. However, etalon elements are arranged at an angle relative to the optical axis, making it difficult to reduce the size of the optical resonator itself or the laser device.

[0004] Reference List

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-84390 Summary of the Invention

[0007] The problem this disclosure aims to solve

[0008] One aspect of this disclosure provides an optical resonator that can be miniaturized even when a wavelength band limiting element is incorporated into the optical resonator, a component of the optical resonator, and a laser device.

[0009] Solution to the problem

[0010] To address the aforementioned problems, this disclosure includes: a laser medium disposed between a pair of reflective elements and emitting emitted light excited by a predetermined excitation light; and a wavelength band limiting element disposed on the emitting side of the emitted light between the pair of reflective elements, the wavelength band limiting element comprising two reflective surfaces orthogonal to the optical axis of the laser medium, and the wavelength band limiting element limiting the wavelength band of the emitted light; and the wavelength band limiting element being positioned to prevent the generation of resonant components outside the intended wavelength range of the wavelength band limiting element between the reflective element located on the laser beam emitting side of the pair of reflective elements and the wavelength band limiting element.

[0011] Wavelength band limiting elements and reflective elements on the laser beam emitting side can be adjacent to each other.

[0012] The distance between the wavelength band limiting element and the reflective component on the laser beam emitting side can be within 50 micrometers.

[0013] It may further include a saturable absorber disposed between the laser medium and the wavelength band limiting element, the transmittance of which increases according to the absorption of emitted light emitted from the laser medium.

[0014] A saturable absorber can be located in two reflective planes, and the transmittance of the saturable absorber increases as the emitted light from the laser medium is absorbed.

[0015] A spacer layer can be placed between the laser medium and the wavelength band limiting element.

[0016] The spacer layer can be placed between the saturable absorber and the wavelength band limiting element.

[0017] The saturable absorber may include: a crystal including a first to a third crystal axis orthogonal to each other; and the saturable absorber may be configured in an optical resonator to have correspondingly different transmittances relative to emitted light rays in two orthogonal polarization directions emitted from the laser medium.

[0018] The saturable absorber can be located in two reflecting planes. The transmittance of the saturable absorber increases with the absorption of the emitted light emitted from the laser medium. The saturable absorber can include a crystal including a first to a third crystal axis orthogonal to each other, and can be arranged in an optical resonator to have different transmittances relative to the emitted light emitted from the laser medium in two orthogonal polarization directions.

[0019] The saturable absorber can be located in two reflective planes. The transmittance of the saturable absorber increases according to the absorption of the emitted light emitted from the laser medium. The saturable absorber may include: a crystal including a first to a third crystal axis orthogonal to each other, and the saturable absorber may be arranged in an optical resonator to have correspondingly different transmittances relative to the emitted light emitted from the laser medium in two polarization directions orthogonal to each other; and a spacer layer may be provided between the laser medium and the wavelength band confinement element.

[0020] At least one of the pair of reflective elements may include a polarizing element, and the polarizing element may have a different reflectivity relative to the emitted light rays in polarization directions that are orthogonal to each other.

[0021] The plane located on the laser beam emitting side among two reflecting planes orthogonal to the optical axis can constitute the reflecting component on the laser beam emitting side of a pair of reflecting components.

[0022] It may further include a heat dissipation substrate disposed on the side opposite to the laser beam emitting side of the laser medium.

[0023] Polarizing elements may include photonic crystals with periodic structures made of inorganic materials.

[0024] It may include the optical resonator as described above; and an excitation source unit that emits excitation light into the laser medium.

[0025] To address the aforementioned problems, this disclosure provides a component of an optical resonator comprising: a saturable absorber having a transmittance increased by the absorption of emitted light already emitted from a laser medium; and two reflective planes parallel to each other and included on two sides of the saturable absorber.

[0026] To address the aforementioned problems, this disclosure provides a component of an optical resonator, comprising: a pair of reflective elements constituting an optical resonator; and a wavelength band limiting element disposed on the emission side of the emitted light between the pair of reflective elements. The wavelength band limiting element includes two reflective planes orthogonal to the optical axis of the optical resonator, and the wavelength band limiting element limits the wavelength band of the emitted light. The plane on the emission side of the two reflective planes orthogonal to the optical axis constitutes the reflective element on the emission side of the pair of reflective elements. Attached Figure Description

[0027] Figure 1 This is a diagram illustrating an example configuration of a laser device according to this embodiment.

[0028] Figure 2 This is a schematic diagram illustrating resonance in a resonator with a wavelength band-limiting element.

[0029] Figure 3 Is Figure 2 A diagram showing the spectrum of the laser measured in arrangement (a).

[0030] Figure 4 Is Figure 2 (b) is a diagram of the spectrum of the laser measured in the arrangement.

[0031] Figure 5 This is a diagram illustrating the configuration of the optical resonator according to the second embodiment.

[0032] Figure 6 This is a diagram illustrating an example of the configuration of the optical resonator in a variation of the second embodiment.

[0033] Figure 7 This is a diagram illustrating the configuration of an optical resonator according to a third embodiment.

[0034] Figure 8 This is a diagram illustrating an example of the configuration of the optical resonator in a first variation of the third embodiment.

[0035] Figure 9 This is a diagram illustrating an example of a heat dissipation substrate included in an optical resonator in a second variation of the third embodiment.

[0036] Figure 10This is a diagram illustrating the configuration of the optical resonator according to the fourth embodiment.

[0037] Figure 11 This is a diagram illustrating an example of the configuration of the optical resonator in a variation of the fourth embodiment.

[0038] Figure 12 This is a diagram illustrating the configuration of the optical resonator according to the fourth embodiment.

[0039] Figure 13 This is a diagram illustrating an example of the configuration of the optical resonator in a variation of the fifth embodiment.

[0040] Figure 14 This is a diagram showing the configuration of the optical resonator according to the sixth embodiment.

[0041] Figure 15 This is a diagram illustrating an example of the configuration of the optical resonator in a variation of the sixth embodiment. Detailed Implementation

[0042] Hereinafter, embodiments of an optical resonator, its constituent parts, and a laser device will be described with reference to the accompanying drawings. In the following description, focus is placed on the main constituent parts of the optical resonator, its constituent parts, and the laser device; however, the optical resonator, its constituent parts, and the laser device may include constituent parts or functions that are omitted from the illustrations or descriptions. The following description does not exclude constituent parts or functions that are not shown or described.

[0043] (First Embodiment)

[0044] Reference Figure 1 The configuration of the laser device according to this embodiment is described. Figure 1 This is a diagram illustrating an example configuration of a laser device according to this embodiment. The laser device 1 is, for example, a passive Q-switched pulsed laser device, and includes an excitation source unit 2 and an optical resonator 4.

[0045] Excitation source unit 2 emits excitation light 22 that excites the laser medium in optical resonator 4. More specifically, excitation source unit 2 emits excitation light 22 with a wavelength close to 808 nm, which excites, for example, an Nd:YAG crystal serving as the laser medium. Furthermore, if excitation source unit 2 allows the excitation light 22 to be incident on the laser medium in optical resonator 4, then excitation source unit 2 does not need to include an optical system such as a lens.

[0046] The optical resonator 4 emits a laser beam excited by the excitation light 22 emitted by the excitation light source unit 2. The optical resonator 4 includes a laser medium 11, a pair of reflective components 12, a saturable absorber 14, and a wavelength band limiting element 15. It should be noted that in this embodiment, it is assumed that the excitation light input side is the "upstream side" and the oscillating laser output side is the "downstream side".

[0047] The laser medium 11, for example, is an Nd:YAG crystal, disposed between a pair of reflective elements 12 constituting the optical resonator 4, and emits emitted light excited by a predetermined excitation light. More specifically, the laser medium 11 is excited by excitation light 22 having a wavelength of approximately 808 nm. The laser medium 11 then emits light with a wavelength of approximately 1064 nm, which transitions from an upper energy level to a lower energy level. Note that in the following description, the light emitted by the laser medium 11 is referred to as emitted light 21.

[0048] Reflector 12A and output reflector 12B constitute a pair of reflecting components 12. Reflector 12A is, for example, a reflector that transmits excitation light 22 having a wavelength of approximately 808 nm emitted from excitation source unit 2 and reflects emitted light 21 having a wavelength of approximately 1064 nm emitted from laser medium 11 with a predetermined reflectivity. The use of a reflector as reflector 12A is merely an example and can be appropriately modified. For example, an element comprising multiple dielectric layers can be used as reflector 12A. Note that the above is illustrative and the example is not limited thereto.

[0049] Mirror 12B transmits a portion of light with a wavelength of approximately 1064 nm and reflects the remainder. Note that mirror 12A may be a dielectric multilayer formed on the end face of Nd:YAG crystal 11.

[0050] The transmittance of the saturable absorber 14 increases with the absorption of the emitted light from the laser medium. The saturable absorber 14 comprises, for example, Cr... 4+ The YAG crystal element has the characteristic that its light absorption rate decreases due to light absorption saturation, and it is used as a passive Q-switch in the case of a passive Q-switch pulsed laser device. In other words, if emitted light 21 from the laser medium 11 has entered, the saturable absorber 14 absorbs the emitted light 21, and the transmittance of the saturable absorber 14 increases with absorption. Then, with the increase of electron density in the excitation level and the excitation level being satisfied, the saturable absorber 14 becomes transparent, therefore, the Q value of the optical resonator increases, and laser oscillation occurs.

[0051] For example, the wavelength band limiting element 15 is an etalon element disposed downstream of the saturable absorber 14 and limits the wavelength band of the emitted light 21. The wavelength band limiting element 15 includes two reflective planes orthogonal to the optical axis L of the optical resonator (i.e., the optical axis L of the laser medium 11) and limits the wavelength band of the emitted light 21. For example, emitted light 21 with a wavelength of approximately 1064 nm is transmitted. Note that the etalon element may be uncoated. Alternatively, the etalon element may be partially coated with a reflective film. Additionally, the elements 11, 12, 14, and 15 of the optical resonator 4 may be connected together.

[0052] Next, the operation of the laser device 1 will be described. For example... Figure 1 As shown, if excitation light 22 with a wavelength of approximately 808 nm has been output from excitation source unit 2, the excitation light 22 passes through reflector 12A and enters laser medium 11, exciting laser medium 11 and causing population inversion. Next, if emission light 21 with a wavelength of approximately 1064 nm has been emitted in the excited laser medium 11 due to a transition from an upper energy level to a lower energy level, the emission light 21 enters saturable absorber 14 and is absorbed. If the electron density of the excitation level of saturable absorber 14 has increased due to this absorption and has become saturated, saturable absorber 14 is made transparent. As a result, the Q value of optical resonator 4 increases, generating laser oscillation. Then, wavelength band limiting element 15 limits the band of the laser beam to a wavelength of approximately 1064 nm, and laser 23 is output from reflector 12B.

[0053] Here, for reference Figures 2 to 4 The resonance in the resonator 4 describes the wavelength band-limiting element 15. Figure 2 This is a schematic diagram illustrating the resonance in the resonator 4 of the wavelength band-limiting element 15. As described later, in some cases, the saturable absorber 14 is configured as the wavelength band-limiting element 15. In these cases, the element upstream of the wavelength band-limiting element 15 is the laser medium 11. Therefore, in Figure 2 In the image, the element upstream of the wavelength band limiting element 15 is shown as a laser medium 11 or a saturable absorber 14.

[0054] Figure 2 (a) is a diagram showing the relationship between the first distance R1 between the wavelength band limiting element 15 and the reflector 12B of the pair of reflective components 12 and the second distance R2 between the output side of the laser medium 11 and the wavelength band limiting element 15. Figure 2(b) is a diagram illustrating an example of the wavelength band confinement element 15 being adjacent to the reflector 12B. Here, "adjacent" means, for example, a first distance R1 within 50 micrometers. In other words, "adjacent" means that the wavelength band confinement element 15 and the reflector 12B may or may not be in contact with each other.

[0055] Figure 2 (c) and Figure 2 (d) shows the wavelength of the laser 23 that has been output from the reflector 12B. The horizontal axis represents wavelength, and the vertical axis represents intensity.

[0056] like Figure 2 As shown in (c), resonance occurs between the wavelength band limiting element 15 and the reflector 12B, and transmitted light with an intensity of 0.8 or greater occurs randomly. To prevent this resonance, in conventional methods, an inclined arrangement relative to the optical axis L is used, so that no other resonance occurs with the other reflector in the resonator 4. Therefore, the inclined arrangement relative to the optical axis L makes the structure complex and requires more space. Consequently, it is difficult to use in conjunction with other components, which has a negative impact on the miniaturization of the resonator 4.

[0057] Therefore, in this embodiment, as Figure 2 As shown in (b), the wavelength band limiting element 15 and the reflector 12B are positioned adjacent to each other. In this case, as Figure 2 As shown in (d), resonance between the wavelength band limiting element 15 and the reflector 12B is further prevented, and thus a laser 23 with a frequency band limited by the wavelength band limiting element 15 and having a desired wavelength is output. As described above, resonance between the wavelength band limiting element 15 and the reflector 12B is prevented as the distance R1 decreases. In particular, resonance between the wavelength band limiting element 15 and the reflector 12B is further prevented when the wavelength band limiting element 15 and the reflector 12B are positioned close to each other.

[0058] Figure 3 It is one of them Figure 2 A diagram showing the spectrum of laser 23 measured in arrangement (a). Figure 3 (a) is a diagram in which the horizontal axis represents the average excitation power and the vertical axis represents the average output. Figure 3 (b) is shown in Figure 3 Figure (a) shows a diagram of the spectrum of laser 23 at three points represented by circles. In the figure, the horizontal axis represents wavelength, and the vertical axis represents power. Figure 3 As shown, the spectrum exhibits multiple modes.

[0059] on the contrary, Figure 4 It is one of them Figure 2 A diagram showing the spectrum of laser 23 measured in arrangement (b). Figure 4 (a) is a diagram in which the horizontal axis represents the average excitation power and the vertical axis represents the average output. Figure 4 (b) is shown in Figure 4 Figure (a) shows a plot of the spectrum of laser 23 at a circular point. In the figure, the horizontal axis represents wavelength, and the vertical axis represents power. Figure 4 As shown, preventing resonance allows the spectrum to have a single mode.

[0060] As described above, the wavelength band limiting element 15 is positioned such that, while maintaining the relationship between the two reflecting planes orthogonal to the optical axis L, resonance with the reflector 12B of the reflecting component 12 is prevented. By doing so, resonance is prevented, and laser light 23 with the desired wavelength band can be output from the reflector 12B. Specifically, resonance is further prevented by arranging the wavelength band limiting element 15 adjacent to the reflector 12B. Furthermore, by positioning the wavelength band limiting element 15 in a state where the relationship between the two reflecting planes orthogonal to the optical axis L is maintained, the wavelength band limiting element 15 can be adjacent to or joined to the reflector 12B and the saturable absorber 14, and the size of the optical resonator 4 can be further reduced.

[0061] (Modifications of the first embodiment)

[0062] In the first embodiment, the case where an Nd:YAG crystal is used as the laser medium 11 and a Cr4+:YAG crystal is used as the saturable absorber 14 has been described. However, this is only an example, and the combination of the laser medium 11 and the saturable absorber 14 can be appropriately changed.

[0063] Therefore, in a variation of the first embodiment, for example, Nd can be used. 3+ The laser medium 11 is YAG ceramic (emitting light with a wavelength close to 1064 nm), Nd:YVO4 (emitting light with a wavelength close to 1064 nm), or Yb:YAG (emitting light with a wavelength close to 1030 nm or 1050 nm) instead of Nd:YAG crystal. Furthermore, when using different laser media, an excitation light with the optimal wavelength for excitation is appropriately selected.

[0064] It should be noted that when Nd:YAG, Nd:YVO4 or Yb:YAG is used as the laser medium 11, Cr:YAG, semiconductor saturable absorber mirror (SESAM) and the like are used as saturable absorbers 14.

[0065] Alternatively, Er glass (emitting light 21 with a wavelength close to 1540 nm) can be used as the laser medium 11. It should be noted that when Er glass is used as the laser medium 11, Co... 2+MALO, Co 2+ :LaMgAl, U 2+ CaF2, Er 3+ CaF2 and other substances are used as saturable absorbers 14.

[0066] (Second Embodiment)

[0067] The laser source 1 according to the second embodiment differs from the laser source 1 according to the first embodiment in that at least one of the reflectors 12A or 12B has a polarization function. The differences from the laser source 1 according to the first embodiment are described below.

[0068] Figure 5 This is a diagram showing the configuration of the optical resonator 4 according to the second embodiment. (See diagram for example.) Figure 5 As shown, reflector 12C has a polarization function. Reflector 12A can be a polarizing element, or both reflector 12A and reflector 12C can be polarizing elements. In the optical resonator 4 according to this embodiment, the case where reflector 12C is a polarizing element is described as an example.

[0069] More specifically, the reflector 12C includes a polarization element with polarization selection functionality. The polarization element is an element with different reflectivities relative to the emitted light 21 based on its polarization direction. The reflectivity changes with respect to the emitted light in each orthogonal polarization direction, thus causing laser oscillation in response to the emitted light in the polarization direction that results in higher reflectivity. In other words, the polarization direction of the emitted light is controlled by the polarization element, thereby generating a laser beam with a stable polarization direction.

[0070] There are no particular limitations on the components used as polarizing elements. For example, as the polarizing element according to this embodiment, a photonic crystal polarizing element using a photonic crystal, a wire grid polarizing element using a wire grid, or an orientation polarizing element using a resin material can be used.

[0071] When the output of the laser beam emitted by the laser device 1 is high, the amplitude of the electric field within the optical resonator 4 increases. In other words, the load applied to the polarization element increases, and therefore, it is more preferable to use a polarization element that can withstand the desired output. In this respect, depending on the material, structure, etc., photonic crystals can exhibit higher tolerance to the load applied due to laser oscillation. Furthermore, wire gratings have the characteristic of absorbing emitted light 21, but photonic crystals do not have this characteristic, and therefore photonic crystal polarization elements are likely to achieve a higher oscillation efficiency than wire grating polarization elements. In view of this, the case of using a photonic crystal polarization element as a polarization element according to this embodiment is described as an example. It should be noted that in order for the laser to oscillate more effectively in response to emitted light 21 in the desired polarization direction, it is preferable that the reflectivity difference of the photonic crystal polarization element relative to the light emitted light 21 in mutually orthogonal polarization directions is 1% or greater. However, this is not limiting, and the difference in reflectivity of the photonic crystal polarization element relative to the light emitted light 21 in mutually orthogonal polarization directions can be appropriately varied.

[0072] Furthermore, to enable more efficient laser oscillation and increase impedance, it is preferable that the thickness of each photonic crystal layer included in the photonic crystal polarization element is approximately the same as the wavelength of the emitted light 21. However, this is not limiting, and the thickness of each photonic crystal layer can be appropriately varied. For example, the thickness of each photonic crystal layer can be smaller (or larger) than the wavelength of the emitted light 21 by a predetermined value. Furthermore, as the material of the photonic crystal, for example, SiO2, SiN, Ta2O5, etc., can be used. However, this is not limiting, and the material of the photonic crystal can be appropriately varied.

[0073] As described above, in the laser device 1 according to this embodiment, one of the pair of reflecting components 12 is a polarizing element. By doing so, the length of the optical resonator is reduced compared to the case where the polarizing element is inserted between the pair of reflecting components 12. Therefore, the laser device 1 according to this embodiment can not only generate pulsed laser with a stable polarization direction, but also prevent the increase in pulse width and the decrease in peak intensity due to the increase in the length of the optical resonator, and can achieve miniaturization of the optical resonator 4 and the laser device 1.

[0074] (A variation of the second embodiment)

[0075] Figure 6 This is a diagram illustrating an example configuration of the optical resonator 4 in a variation of the second embodiment. (See diagram for example.) Figure 6As shown, the spacer layer s1 may be included in the optical resonator 4. For example, the spacer layer s1 may include an air layer or a dielectric layer. The spacer layer s1 may be used, for example, to adjust the pulse width and peak intensity of the laser beam 23. Furthermore, the spacer layer s1 may be included between the laser medium 11 and the saturable absorber 14.

[0076] (Third Embodiment)

[0077] The laser source 1 according to the third embodiment differs from the laser source 1 according to the second embodiment in that the saturable absorber is included in two reflective planes within the wavelength band limiting element. The differences from the laser source 1 according to the second embodiment are described below.

[0078] Figure 7 This is a diagram showing the configuration of the optical resonator 4 according to the third embodiment. Figure 7 As shown, the wavelength band limiting element 16 includes saturable absorbers in two reflective planes within the wavelength band limiting element. More specifically, the wavelength band limiting element 16 includes: a saturable absorber, wherein the transmittance increases according to the absorption of emitted light emitted from the laser medium; and two reflective plane portions, parallel to each other and included in two sides of the saturable absorber.

[0079] As described above, in the laser device 1 according to this embodiment, the saturable absorber is included in two reflective planes within the wavelength band limiting element 16. By doing so, the length of the optical resonator can be further reduced compared to the case where only the saturable absorber 14 and the wavelength band limiting element 15 are included. Therefore, the laser device 1 according to this embodiment can further prevent the increase in pulse width and the decrease in peak intensity caused by the increase in the length of the optical resonator, and can further miniaturize the optical resonator 4 and the laser device 1.

[0080] (First variation of the third embodiment)

[0081] Figure 8 This is a diagram illustrating an example of the configuration of the optical resonator 4 in a first variation of the third embodiment. (See diagram for example.) Figure 8 As shown, the spacer layer s2 may be included in the optical resonator 4. For example, the spacer layer s2 may include an air layer or a dielectric layer. The spacer layer s2 may be used, for example, to adjust the pulse width and peak intensity of the laser beam 23.

[0082] (Second variation of the third embodiment)

[0083] Figure 9 This is a diagram illustrating an example in a second variation of the third embodiment where a heat dissipation substrate el is included within the optical resonator 4. (See diagram for example.) Figure 9As shown, the optical resonator 4 may also include a heat dissipation substrate el. For example, the heat dissipation substrate el is made of sapphire. This prevents temperature rise within the optical resonator 4. Furthermore, the optical resonator 4 in the third embodiment includes a heat dissipation substrate el, but is not limited thereto. For example, all optical resonators 4 disclosed in this embodiment (such as those described above) may also be used. Figure 1 , Figure 5 , Figure 6 , Figure 7 , Figure 8 The optical resonator 4 shown below, and the one described later. Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 The optical resonator 4) shown contains a heat dissipation substrate el.

[0084] (Fourth Embodiment)

[0085] The laser source 1 according to the fourth embodiment differs from the laser source 1 according to the first embodiment in that the saturable absorber includes a saturable absorber having a specific crystal orientation. The differences from the laser source 1 according to the first embodiment are described below.

[0086] Figure 10 This is a diagram showing the configuration of the optical resonator 4 according to the fourth embodiment. (See diagram for example.) Figure 10 As shown, the saturable absorber 17 includes a saturable absorber with a specific crystal orientation. This saturable absorber 17 is, for example, a Cr... 4+ YAG crystal. Cr 4+ YAG crystals are anisotropic, and their transmittance for emitted light in mutually orthogonal polarization directions varies depending on the crystal orientation. As a result, laser beams with stable polarization directions can be output. Specifically, in terms of orientation... <110> When used in this context, the difference in transmittance of emitted light rays relative to mutually orthogonal polarization directions may become the greatest, and the polarization direction of the laser beam output from the passive Q-switched laser device can be further stabilized.

[0087] As described above, the laser device 1 according to this embodiment includes a saturable absorber 17 with a specific crystal orientation. Therefore, compared to the case where a polarizing element is inserted between a pair of reflecting components 12, the length of the optical resonator 4 can be further shortened. Thus, the laser device 1 of this embodiment can not only generate pulsed laser with a stable polarization direction, but also prevent the increase in pulse width and decrease in peak intensity due to the increase in the length of the optical resonator 4, and can achieve miniaturization of the optical resonator 4 and the laser device 1.

[0088] (Modifications of the fourth embodiment)

[0089] Figure 11 This is a diagram illustrating an example configuration of the optical resonator 4 in a variation of the fourth embodiment. (See diagram for example.) Figure 11 As shown, a spacer layer s3 may also be included within the optical resonator 4. For example, the spacer layer s3 may include an air layer or a dielectric layer. The spacer layer s3 may be used, for example, to adjust the pulse width and peak intensity of the laser beam 23. Furthermore, the spacer layer may be included between the laser medium 11 and the saturable absorber 17.

[0090] (Fifth Embodiment)

[0091] The laser source 1 according to the fifth embodiment differs from the laser source 1 according to the fourth embodiment in that the saturable absorber having a specified crystal orientation is included in two reflective planes within the wavelength band confinement element. The differences from the laser source 1 according to the fourth embodiment are described below.

[0092] Figure 12 This is a diagram showing the configuration of the optical resonator 4 according to the fifth embodiment. (See diagram for example.) Figure 12 As shown, the wavelength band confinement element 18 includes a saturable absorber having a specified crystal orientation in two reflective planes within the wavelength band confinement element. More specifically, the wavelength band confinement element 18 includes: a saturable absorber having a specified crystal orientation, wherein the transmittance increases according to the absorption of emitted light emitted from the laser medium; and two reflective plane portions, parallel to each other and included on opposite sides of the saturable absorber.

[0093] As described above, in the laser device 1 according to this embodiment, a saturable absorber with a specified crystal orientation is included in two reflecting planes of the wavelength band confinement element 18. By doing so, compared to the case where the saturable absorber 14 and the wavelength band confinement element 15 are included separately, the laser device 1 according to this embodiment is not only able to generate pulsed laser light with a stable polarization direction, but also able to further reduce the length of the optical resonator. Therefore, the laser device 1 according to this embodiment can further prevent the increase in pulse width and the decrease in peak intensity caused by the increase in the length of the optical resonator, and can further miniaturize the optical resonator 4 and the laser device 1.

[0094] (Modifications of the fifth embodiment)

[0095] Figure 13 This is a diagram illustrating an example configuration of the optical resonator 4 in a modified embodiment of the fifth embodiment. (See diagram for example.) Figure 13 As shown, the spacer layer s4 may be included in the optical resonator 4. For example, the spacer layer s4 may include an air layer or a dielectric layer. The spacer layer s4 may be used, for example, to adjust the pulse width and peak intensity of the laser beam 23.

[0096] (Sixth Embodiment)

[0097] The laser source 1 according to the sixth embodiment differs from the laser source 1 according to the second embodiment in that the polarizing mirror and the wavelength band limiting element 15 are arranged as a single unit. The differences from the laser source 1 according to the first embodiment are described below.

[0098] Figure 14 This is a diagram showing the configuration of the optical resonator 4 according to the sixth embodiment. (See diagram for example.) Figure 14 As shown, the output reflector 12D has both etalon function and polarization function. Specifically, the downstream planes of the two reflection planes orthogonal to the optical axis constitute the downstream reflection components of a pair of reflection components 12. Furthermore, the output reflector 12D includes a polarization element with polarization selection function. The polarization element is an element that has different reflectivities and transmittances for the emitted light 21 depending on the polarization direction. The reflectivity changes relative to the emitted light in each orthogonal polarization direction; therefore, laser oscillation occurs in response to the emitted light in the polarization direction that causes higher reflectivity. In other words, the polarization direction of the emitted light is controlled by the polarization element, thus generating a laser beam with a stable polarization direction.

[0099] As described above, in the laser device 1 according to this embodiment, the output reflector 12D is configured as a reflector with polarization function and an element with etalon function. By doing so, the laser device 1 according to this embodiment not only generates pulsed laser with a stable polarization direction, but also further reduces the length of the optical resonator compared to the case where only the reflector 12C and the wavelength band limiting element 15 are included. Therefore, the laser device 1 according to this embodiment can further prevent the increase in pulse width and the decrease in peak intensity caused by the increase in the length of the optical resonator, and can further miniaturize the optical resonator 4 and the laser device 1.

[0100] (A variation of the sixth embodiment)

[0101] Figure 15 This is a diagram illustrating an example configuration of the optical resonator 4 in a variation of the sixth embodiment. (See diagram for example.) Figure 15 As shown, the spacer layer s5 may be included in the optical resonator 4. For example, the spacer layer s5 may include an air layer or a dielectric layer. The spacer layer s5 may be used, for example, to adjust the pulse width and peak intensity of the laser beam 23.

[0102] It should be noted that the laser device 1 according to this embodiment can be applied to various devices, systems, etc. For example, the laser device 1 according to this embodiment can be applied to devices for processing metals, semiconductors, dielectrics, resins, organisms, etc.; distance measurement devices for distance measurement (e.g., optical detection and ranging or laser imaging detection and ranging (LiDAR)); devices for laser-induced breakdown spectroscopy (LIBS); devices for eye refractive index correction operations (e.g., LASIK); devices for depth sensing; or LiDAR for atmospheric observation of aerosols, etc. It should be noted that the devices to which the laser device 1 according to this embodiment is applied are not limited to the above.

[0103] It should be noted that this technology can be implemented using the configuration described below.

[0104] (1) An optical resonator, comprising:

[0105] A laser medium, arranged between a pair of reflective elements, emits light that has been excited by a predetermined excitation light; and

[0106] A wavelength band limiting element is arranged between a pair of reflective elements on the emitting side of the emitted light. The wavelength band limiting element includes two reflective planes orthogonal to the optical axis of the laser medium, and the wavelength band limiting element restricts the wavelength band of the emitted light.

[0107] In this configuration, while maintaining its relationship with the optical axis, the wavelength band limiting element is positioned to prevent resonance with the reflective component located on the emitting side of the laser beam in one of a pair of reflective components.

[0108] (2) The optical resonator according to (1), wherein the wavelength band limiting element and the reflective element on the emitting side of the laser beam are adjacent to each other.

[0109] (3) The optical resonator according to (1) or (2), wherein the distance between the wavelength band limiting element and the reflective element on the laser beam emitting side is within 50 micrometers.

[0110] (4) The optical resonator according to any one of (1) to (3) further includes a saturable absorber disposed between the laser medium and the wavelength band limiting element, the transmittance of the saturable absorber increasing according to the absorption of emitted light emitted from the laser medium.

[0111] (5) An optical resonator according to any one of (1) to (3), wherein the saturable absorber is located in two reflective planes and the transmittance of the saturable absorber increases according to the absorption of the emitted light already emitted from the laser medium.

[0112] (6) The optical resonator according to (5), wherein the spacer layer is disposed between the laser medium and the wavelength band limiting element.

[0113] (7) The optical resonator according to (4), wherein the spacer layer is disposed between the saturable absorber and the wavelength band limiting element.

[0114] (8) An optical resonator according to any one of (4) to (7), wherein the saturable absorber comprises a crystal comprising a first to a third crystal axis orthogonal to each other, and the saturable absorber in the optical resonator is configured to have different transmittances relative to the emitted light rays in two orthogonal polarization directions emitted from the laser medium.

[0115] (9) The optical resonator according to (8), wherein the spacer layer is disposed between the saturable absorber and the wavelength band limiting element.

[0116] (10) The optical resonator according to (1), wherein the saturable absorber is located in two reflecting planes, the transmittance of the saturable absorber increases according to the absorption of the emitted light emitted from the laser medium, and the saturable absorber comprises: a crystal including a first crystal axis to a third crystal axis orthogonal to each other, and the saturable absorber in the optical resonator is configured to have correspondingly different transmittances relative to the rays of the emitted light with two orthogonal polarization directions emitted from the laser medium.

[0117] (11) The optical resonator according to (1), wherein the saturable absorber is located in two reflecting planes, the transmittance of the saturable absorber increases according to the absorption of the emitted light emitted from the laser medium, the saturable absorber comprising: a crystal including a first to a third crystal axis orthogonal to each other, and configured in the optical resonator to have different transmittances relative to the emitted light rays in two orthogonal polarization directions emitted from the laser medium, and a spacer layer is provided between the laser medium and the wavelength band confinement element.

[0118] (12) An optical resonator according to any one of (1) to (11), wherein at least one of the pair of reflective elements includes a polarizing element, and the polarizing element has a different reflectivity relative to the rays of emitted light in polarization directions that are orthogonal to each other.

[0119] (13) An optical resonator according to any one of (1) to (12), wherein the planes on the laser beam emitting side of two reflecting planes orthogonal to the optical axis constitute a pair of reflecting components on the laser beam emitting side.

[0120] (14) The optical resonator according to any one of (1) to (13) further includes a heat dissipation substrate disposed on the side opposite to the emitting side of the laser beam of the laser medium.

[0121] (15) The optical resonator according to (12), wherein the polarization element comprises a photonic crystal having a periodic structure of inorganic material.

[0122] (16) A laser device, comprising:

[0123] An optical resonator based on any one of (1) to (15); and

[0124] The excitation light source unit is activated so that the excitation light is emitted into the laser medium.

[0125] (17) A component of an optical resonator, the component comprising:

[0126] A saturable absorber has an increased transmittance based on the absorption of emitted light already emitted from the laser medium; and two reflective plane portions, parallel to each other and included on both sides of the saturable absorber.

[0127] (18) A component of an optical resonator, the component comprising:

[0128] A pair of reflective components constitute an optical resonator; and

[0129] A wavelength band limiting element is arranged on the emitting side of the emitted light between a pair of reflective elements. The wavelength band limiting element includes two reflective planes orthogonal to the optical axis of the optical resonator, and the wavelength band limiting element limits the wavelength band of the emitted light.

[0130] Among them, the plane located on the emitting side of the emitted light in the two reflecting planes orthogonal to the optical axis constitutes the emitting side of the emitting light in a pair of reflecting components.

[0131] This disclosure is not limited to the embodiments described above, but also includes various modifications that can be conceived by those skilled in the art, and the effects of this disclosure are not limited to the foregoing. In other words, various additions, changes, and partial deletions can be made without departing from the conceptual idea and spirit of this disclosure as defined by the claims and their equivalents.

[0132] List of reference numerals

[0133] 1. Laser equipment; 2. Excitation source unit; 4. Optical resonator; 11. Laser medium; 12A. A pair of reflecting components; 12A. Reflector; 12B, 12C, 12D. Output reflectors; 14. Saturable absorber; 15, 16. Wavelength band limiting element; 17. Saturable absorber; 18. Wavelength band limiting element; s1 to s5. Spacer layer; e1. Heat dissipation substrate.

Claims

1. An optical resonator, comprising: A laser medium is arranged between a pair of reflective components and emits emitted light that has been excited by a predetermined excitation light; as well as A wavelength band limiting element is disposed on the emitting side of the emitted light between the pair of reflective components. The wavelength band limiting element includes two reflective planes orthogonal to the optical axis of the laser medium and limits the wavelength band of the emitted light. The wavelength band limiting element contacts the incident surface of the reflective component located on the laser beam emission side of the pair of reflective components to prevent resonance between the reflective component located on the laser beam emission side of the pair of reflective components and the wavelength band limiting element, thereby outputting the resonant component of the expected wavelength range of the wavelength band limiting element.

2. The optical resonator according to claim 1, further comprising a saturable absorber. The saturable absorber is disposed between the laser medium and the wavelength band confinement element, and the transmittance of the saturable absorber increases with the absorption of the emitted light emitted from the laser medium.

3. The optical resonator according to claim 2, wherein, A spacer layer is disposed between the saturable absorber and the laser medium or the wavelength band limiting element.

4. The optical resonator according to claim 1, wherein, The saturable absorber is located in the two reflective planes, and the transmittance of the saturable absorber increases with the absorption of the emitted light emitted from the laser medium.

5. The optical resonator according to claim 4, wherein, A spacer layer is disposed between the laser medium and the wavelength band limiting element.

6. The optical resonator according to claim 2, wherein, The saturable absorber includes a crystal comprising a first to a third crystal axis orthogonal to each other, and the saturable absorber is configured in the optical resonator to have different transmittances for the emitted light rays in two orthogonal polarization directions emitted from the laser medium.

7. The optical resonator according to claim 6, wherein, A spacer layer is disposed between the saturable absorber and the laser medium or the wavelength band limiting element.

8. The optical resonator according to claim 1, wherein, A saturable absorber is located in the two reflecting planes, the transmittance of the saturable absorber increases with the absorption of the emitted light emitted from the laser medium, and the saturable absorber comprises a crystal including a first to a third crystal axis orthogonal to each other, and the saturable absorber is configured in the optical resonator to have different transmittances for the emitted light rays with two orthogonal polarization directions emitted from the laser medium.

9. The optical resonator according to claim 1, wherein, A saturable absorber is located in the two reflecting planes, and the transmittance of the saturable absorber increases with the absorption of the emitted light emitted from the laser medium. The saturable absorber includes a crystal comprising a first to a third crystal axis orthogonal to each other, and is configured in the optical resonator to have different transmittances for the emitted light rays in two orthogonal polarization directions emitted from the laser medium. A spacer layer is disposed between the laser medium and the wavelength band confinement element.

10. The optical resonator according to claim 1, wherein, At least one of the pair of reflective elements includes a polarizing element, and the polarizing element has a different reflectivity for the emitted light rays in polarization directions that are orthogonal to each other.

11. The optical resonator according to claim 1, wherein, The plane on the emitting side of the laser beam in one of the two reflecting planes orthogonal to the optical axis is integrally configured with the reflecting component on the emitting side of the laser beam in one of the pair of reflecting components.

12. The optical resonator according to claim 10, wherein, The polarization element includes a photonic crystal with a periodic structure made of inorganic material.

13. The optical resonator according to claim 1, further comprising a heat dissipation substrate, The heat dissipation substrate is disposed on the side opposite to the laser beam emitting side of the laser medium.

14. A laser device, comprising: The optical resonator according to claim 1; as well as The excitation light source unit is activated so that the excitation light is emitted into the laser medium.

15. A component of an optical resonator, the component comprising: A pair of reflective components constitute the optical resonator; A laser medium is disposed between the pair of reflective components, and A wavelength band limiting element is disposed between the pair of reflective elements on the emitting side of the emitted light and limits the wavelength band of the emitted light, the wavelength band limiting element comprising: A saturable absorber having a transmittance that increases according to the absorption of emitted light emitted from the laser medium; as well as Two reflective plane portions are parallel to each other and orthogonal to the optical axis of the laser medium, and the two reflective plane portions are included on two sides of the saturable absorber to prevent resonance between the reflective component on the emitting side of the pair of reflective components and the wavelength band limiting element, thereby outputting the resonant component of the expected wavelength range of the wavelength band limiting element.

16. A component of an optical resonator, the component comprising: A pair of reflective components constitute the optical resonator; as well as A wavelength band limiting element is arranged between the pair of reflective components on the emitting side of the emitted light. The wavelength band limiting element includes two reflective planes orthogonal to the optical axis of the optical resonator and limits the wavelength band of the emitted light. Among the two reflecting planes orthogonal to the optical axis, the plane located on the emission side of the emitted light constitutes the reflecting component on the emission side of the emitted light in the pair of reflecting components. The wavelength band limiting element prevents resonance between the reflective component on the emitting side of the pair of reflective components and the wavelength band limiting element, thereby outputting the resonant component of the expected wavelength range of the wavelength band limiting element.

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