Laser element and laser device

Abstract

[Problem] To provide a laser element capable of stabilizing laser beam outputs. [Solution] A laser element according to the present disclosure comprises: an excitation light source having a first reflection layer having the highest reflectance with respect to excitation light having a first designed wavelength; a solid-state laser medium disposed on the emission direction side of the excitation light with respect to the excitation light source; a second reflection layer provided between the excitation light source and the solid-state laser medium and having the highest reflectance with respect to laser light having a second designed wavelength longer than the first designed wavelength; and a third reflection layer disposed on the emission direction side of the laser light with respect to the solid-state laser medium and having the highest reflectance with respect to the excitation light. An interval between the first reflection layer and the second reflection layer is designed such that wavelengths of plurality of longitudinal modes of excitation light including the first designed wavelength are present within the FWHM of the absorption spectrum of the solid-state laser medium.

Description

Laser element and laser device

[0001] The present disclosure relates to a laser element and a laser device.

[0002] Laser technology is applied in multiple fields, such as micromachining, medical equipment, and distance measurement. In particular, short-pulse laser technology is expected to be applied to high-precision processing technology and highly efficient wavelength conversion technology. Using solid-state lasers, peak power exceeding MW can be obtained.

[0003] A known laser element used in the above laser technology has a structure in which an excitation light source and a solid-state laser medium are stacked and integrated together, which makes it possible to make the laser element ultra-compact.

[0004] International Publication No. 2021 / 106757

[0005] In a laser device that integrates a pumping light source and a solid-state laser medium, the oscillation wavelength of the pumping light may shift due to variations in the cavity length caused by manufacturing variations in the pumping light source or changes in the environmental temperature. In this case, if the optical absorption spectrum width of the solid-state laser medium is very narrow, the pumping light is difficult to absorb by the solid-state laser medium. In this case, it becomes difficult for the solid-state laser medium to stabilize its laser oscillation.

[0006] The present disclosure provides a laser element capable of stabilizing the output of laser light.

[0007] A laser element according to one aspect of the present disclosure includes: an excitation light source having a first reflective layer with the highest reflectivity for excitation light having a first design wavelength; a solid-state laser medium arranged in an emission direction of the excitation light with respect to the excitation light source; a second reflective layer provided between the excitation light source and the solid-state laser medium and having the highest reflectivity for laser light having a second design wavelength longer than the first design wavelength; and a third reflective layer arranged in an emission direction of the laser light with respect to the solid-state laser medium and having the highest reflectivity for the excitation light. A spacing between the first reflective layer and the second reflective layer is designed such that wavelengths of multiple longitudinal modes of the excitation light, including the first design wavelength, exist within a half width of an absorption spectrum of the solid-state laser medium.

[0008] The laser element may further include a fourth reflective layer disposed on the side of the third reflective layer in the emission direction of the laser light, and a saturable absorber provided between the fourth reflective layer and the third reflective layer.

[0009] The excitation light source may further include a semiconductor substrate provided between the first reflective layer and the second reflective layer.

[0010] The excitation light source may further include a dielectric substrate provided between the first reflective layer and the second reflective layer.

[0011] The dielectric substrate may be a sapphire substrate.

[0012] The material of the saturable absorber may be YAG doped with Cr (chromium).

[0013] The material of the saturable absorber is Co (cobalt) doped spinel (MgAl ２ O ４ ) may also be used.

[0014] The laser element may further include a temperature regulator that adjusts the temperature of at least one of the excitation light source and the solid-state laser medium.

[0015] The excitation light source may further include a fifth reflective layer provided between the first reflective layer and the second reflective layer, and the fifth reflective layer may have a higher transmittance of the excitation light than the first reflective layer.

[0016] The excitation light source may further include an active layer provided between the first reflective layer and the second reflective layer.

[0017] A laser device according to one aspect of the present disclosure includes a plurality of the above laser elements.

[0018] The plurality of laser elements may be arranged in a one-dimensional array or a two-dimensional array.

[0019] The laser device may further include a drive circuit configured to supply an electric signal for driving at least one of the laser elements.

[0020] 17 is a cross-sectional view schematically showing a laser element according to a first embodiment. FIG. 18 is an exploded cross-sectional view of the laser element shown in FIG. 1. FIG. 19 is a diagram showing an example of an optical waveform generated by a resonance operation in the laser element according to the first embodiment. FIG. 19 is an exploded cross-sectional view of a laser element according to a comparative example. FIG. 19 is a diagram showing an example of an optical waveform generated by a resonance operation in the laser element according to the comparative example. FIG. 19 is a diagram showing an example of longitudinal mode characteristics of excitation light according to the comparative example. FIG. 20 is a diagram showing an example of an absorption spectrum of a solid-state laser medium. FIG. 21 is a diagram showing longitudinal mode characteristics and an absorption spectrum of the laser element according to the first embodiment. FIG. 21 is a diagram showing an example of the reflection characteristics of a reflective layer of the laser element according to the first embodiment. FIG. 22 is a diagram showing an example of the relationship between the light intensity and wavelength of excitation light according to the first embodiment. FIG. 22 is an exploded cross-sectional view of a laser element according to a second embodiment. FIG. 23 is an exploded cross-sectional view of a laser element according to a third embodiment. FIG. 24 is an exploded cross-sectional view of a laser element according to a fourth embodiment. FIG. 25 is a diagram showing a laser device according to a fifth embodiment. FIG. 26 is a diagram showing an example of a laser device according to a first modification. FIG. 27 is a diagram showing an example of a laser device according to a second modification.

[0021] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0022] First Embodiment FIG. 1 is a cross-sectional view schematically illustrating a laser device according to a first embodiment. The laser device 1 according to this embodiment includes an excitation light source 10, a solid-state laser medium 20, and a saturable absorber 30. In the laser device 1, the excitation light source 10, the solid-state laser medium 20, and the saturable absorber 30 are arranged so as to be stacked along the optical axis direction (Z-axis direction). The laser device 1 has a substantially cylindrical shape. Here, the term "substantially cylindrical" includes shapes such as a substantially parallelepiped, a substantially circular cylinder, a substantially elliptical cylinder, a substantially triangular cylinder, and a substantially polygonal cylinder, and the shape of the bottom surface is not limited. However, the laser device 1 may have other shapes.

[0023] Fig. 2 is an exploded cross-sectional view of the laser device 1 shown in Fig. 1. For the sake of explanation, Fig. 2 shows the laser device 1 divided into the pumping light source 10, the solid-state laser medium 20, and the saturable absorber 30. However, the actual laser device 1 may have a structure without gaps between layers, or may have a structure with gaps between components.

[0024] The excitation light source 10 has a semiconductor substrate 11, a contact layer 12, a reflective layer 13 (fifth reflective layer), a cladding layer 14, an active layer 15, a cladding layer 16, a reflective layer 17 (first reflective layer), and an electrode layer 18. These components are arranged along the optical axis direction.

[0025] The semiconductor substrate 11 is disposed at an end of the excitation light source 10 in the emission direction of the excitation light L1. The semiconductor substrate 11 is, for example, an n-type GaAs substrate. However, the semiconductor substrate 11 may be made of other types of compound semiconductors or silicon semiconductors.

[0026] A contact layer 12 is in contact with the surface of the semiconductor substrate 11 opposite to the emission direction of the excitation light L1. The contact layer 12 is made of, for example, an n-type semiconductor. This n-type semiconductor can be formed by doping silicon with, for example, P (phosphorus) or As (arsenic).

[0027] A reflective layer 13 is in contact with the surface of the contact layer 12 opposite to the emission direction of the excitation light L1. The reflective layer 13 is, for example, a DBR (Distributed Bragg Reflector) in which different semiconductor materials are alternately stacked with an optical film thickness of a quarter wavelength.

[0028] A cladding layer 14 is formed on the surface of the reflective layer 13 opposite to the emission direction of the pumping light L1. An active layer 15 is formed on the surface of the cladding layer 14 opposite to the emission direction of the pumping light L1. A cladding layer 16 is formed on the surface of the active layer 15 opposite to the emission direction of the pumping light L1.

[0029] The active layer 15 is made of a material, such as InGaN, AlGaN, InGaP, or AlGaInP, that has a smaller band gap and a larger refractive index than the cladding layers 14 and 16. The active layer 15 may also include a quantum well or multiple quantum wells.

[0030] A reflective layer 17 is formed on the surface of the cladding layer 16 opposite to the emission direction of the excitation light L1. The reflective layer 17 is, for example, a DBR (p-DBR) in which different p-type compound semiconductors are alternately stacked with an optical film thickness of ¼ wavelength. The reflective layer 17 can be made of, for example, AlAs or AlGaAs. However, the material of the reflective layer 17 is not limited to the above materials.

[0031] An electrode layer 18 is formed on the surface of the reflective layer 17 opposite to the emission direction of the excitation light L1. The electrode layer 18 is, for example, a p-type semiconductor. This p-type semiconductor can be formed by doping silicon with, for example, boron (B) or aluminum (Al).

[0032] Following the description of the pumping light source 10, the solid-state laser medium 20 will now be described. The solid-state laser medium 20 includes a solid-state material such as a YAG (yttrium aluminum garnet) crystal doped with Yb (ytterbium) as a laser medium. In this case, the oscillation wavelength of the solid-state laser medium 20 is 1030 nm. For example, the laser medium of the solid-state laser medium 20 can be made of at least one of Nd:YAG, Nd:YVO4, Nd:YLF, Nd:glass, Yb:YAG, Yb:YLF, Yb:FAP, Yb:SFAP, Yb:YVO, Yb:glass, Yb:KYW, Yb:BCBF, Yb:YCOB, Yb:GdCOB, and YB:YAB. The solid-state laser medium 20 may be a four-level laser medium or a three-level laser medium.

[0033] A reflective layer 21 (third reflective layer) is formed on a surface of the solid-state laser medium 20 facing the emission direction of the laser light L2. Also, a reflective layer 22 (second reflective layer) is formed on a surface of the solid-state laser medium 20 facing the excitation light source. The reflective layer 21 is a high reflector (HR) that has a high reflectance for the first design wavelength of the excitation light L1. On the other hand, the reflective layer 22 is a partial reflector (PR) that transmits the excitation light L1 while reflecting the laser light L2.

[0034] Following the solid-state laser medium 20 described above, the saturable absorber 30 will be described. The saturable absorber 30 is a passive Q-switching element. The saturable absorber 30 includes, for example, a YAG (Cr:YAG) crystal doped with Cr (chromium). The saturable absorber 30 exhibits saturable absorption characteristics with respect to the optical intensity of the laser light L2 passing through the saturable absorber 30. V:YAG can also be used as the saturable absorber 30. However, other types of saturable absorbers may also be used as the saturable absorber 30. An active Q-switching element may also be used as the saturable absorber 30.

[0035] A reflective layer 31 (fourth reflective layer) is provided on the surface of the saturable absorber 30 facing the emission direction of the laser light L2. The reflective layer 31 reflects the laser light L2. The reflective layer 31 may be a semi-transparent layer that transmits part of the laser light L2.

[0036] In the laser device 1 configured as described above, the components arranged from the reflective layer 17 to the reflective layer 22 form a first resonator 41. The reflective layer 22, the solid-state laser medium 20, and the reflective layer 21 form a second resonator 42. The first resonator 41 and the second resonator 42 constitute an excitation light resonator 43. The excitation light resonator 43 is capable of resonating an electromagnetic wave with a wavelength of, for example, 885 nm.

[0037] In the laser device 1 according to this embodiment, the components arranged from the reflective layer 22 to the reflective layer 31 form a solid-state laser resonator 44. The solid-state laser resonator 44 is capable of resonating an electromagnetic wave with a wavelength of, for example, 1030 nm.

[0038] In the laser device 1 according to this embodiment, in order to prevent the excitation light L1 from oscillating between the reflection layer 17 and the reflection layer 13, it is desirable that the reflectance of the reflection layer 13 with respect to electromagnetic waves of at least the design wavelength is lower than the reflectance of the reflection layer 17. In other words, it is desirable that the reflection layer 13 has a higher transmittance for the excitation light L1 than the reflection layer 17.

[0039] Next, the operation of the laser device 1 will be described with reference to FIGS.

[0040] 3 is a diagram showing an example of an optical waveform generated by a resonating operation in the laser device 1 according to the first embodiment. In this embodiment, the resonator length L ＯＲ１ That is, the distance between the reflective layer 17 and the reflective layer 12 is designed based on the design wavelength of 885 nm. As a result, the 885 nm wavelength component of the spontaneous emission light forms a standing wave between the reflective layer 17 and the reflective layer 21 and is amplified by the active layer 15.

[0041] The solid-state laser medium 20 exists in the optical path of the pumping light L1. The optical absorption wavelength band of the solid-state laser medium 20 includes the first design wavelength (oscillation wavelength) of 885 nm of the pumping light L1. Therefore, the solid-state laser medium 20 is excited, and a population inversion is formed in the solid-state laser medium 20. Since the pumping light L1 is amplified by stimulated emission, the pumping optical resonator 43 oscillates as a laser at a wavelength of 885 nm.

[0042] A portion of the light from the excitation light resonator 43 that passes through the reflective layer 21 enters the saturable absorber 30 in the solid-state laser resonator 44. The entered light begins to travel back and forth within the solid-state laser resonator 44, which includes the solid-state laser medium 20 and the saturable absorber 30. As the light intensity increases, the saturable absorber 30 absorbs the light and excites electrons in the ground level, temporarily suppressing oscillation within the solid-state laser resonator 44. In the solid-state laser medium 20, stimulated emission is suppressed, and the number of electrons in the excited level increases. After a certain period of time, the excited level of the saturable absorber 30 is filled with electrons, and the light absorption rate by the saturable absorber 30 decreases. Stimulated emission occurs in the solid-state laser medium 20, and the solid-state laser resonator 44 oscillates at a wavelength of 1030 nm. At this time, the energy stored in the excited level of the solid-state laser medium 20 is emitted from the reflective layer 31 to the outside of the laser device 1 as pulsed laser light L3.

[0043] When the pulsed laser beam L3 is emitted, the light intensity within the solid-state laser resonator 44 decreases. As a result, a vacancy is created in the excitation level of the saturable absorber 30, and the light absorption rate by the saturable absorber 30 increases again. The solid-state laser resonator 44 continues to be supplied with the pumping light L1 from the pumping light resonator 43 that has passed through the reflective layer 21. As a result, the light intensity within the solid-state laser resonator 44 increases again, and the above-mentioned process is repeated. As a result, the laser element 1 repeatedly emits pulsed laser beam L3.

[0044] As described above, the saturable absorber 30 functions as a passive Q switch that changes the optical loss due to absorption in accordance with the optical intensity within the resonator and generates pulsed laser light L3. When the saturable absorber 30 is used as a passive Q switch, the higher the gain of the solid-state laser medium 20, the smaller the pulse time width of the generated pulsed laser light L3 can be. Meanwhile, the pulse time width is proportional to the resonator length of the solid-state laser resonator 44.

[0045] Here, a laser device 100 to be compared with the laser device 1 according to the first embodiment will be described.

[0046] Fig. 4 is an exploded cross-sectional view of a laser device 100 according to a comparative example. In Fig. 4, components similar to those of the laser device 1 according to the first embodiment described above are denoted by the same reference numerals, and redundant explanations will be omitted. In the laser device 100 shown in Fig. 4, a first resonator 410 is composed of components arranged from the reflective layer 17 to the reflective layer 13. Furthermore, a second resonator 420 is composed of components arranged from the reflective layer 13 to the reflective layer 22.

[0047] 5 is a diagram showing an example of an optical waveform generated by the resonant operation in the laser device 100 according to the comparative example. As shown in FIG. 5, the resonator length L ＯＲ１ However, the resonator length L of the first resonator 41 according to the first embodiment ＯＲ１ is shorter than.

[0048] 6 is a diagram showing an example of longitudinal mode characteristics of the pump light L1 according to a comparative example. In FIG. 6, the horizontal axis indicates the wavelength of the light, and the vertical axis indicates the intensity of the light. Here, the longitudinal mode indicates a frequency that can be generated as the pump light L1 by the resonance of the first resonator 410 (or the first resonator 41). In this comparative example, the number of longitudinal modes present within a certain wavelength range is determined by the resonator length L of the first resonator 410. ＯＲ１ In the example shown in FIG. 6, the resonator length L of the first resonator 41 is set so that a longitudinal mode is generated at a wavelength of 885 nm. ＯＲ１ has been designed.

[0049] However, if the thickness of the semiconductor material varies when forming the components in the first resonator 410 by epitaxial growth, or if the environmental temperature of the excitation light source 10 changes, the resonator length L ＯＲ１ For example, the resonator length L ＯＲ１ When the cavity length L is increased by 0.2%, the longitudinal mode of the pump light L1 may shift by about 2 nm in the longer direction as shown in FIG. ＯＲ１ When the length of the excitation light L1 is reduced by 0.2%, the longitudinal mode of the excitation light L1 may shift by approximately 2 nm in the shorter direction.

[0050] FIG. 7 is a diagram showing an example of the absorption spectrum of the solid-state laser medium 20. In FIG. 7, the horizontal axis represents the wavelength of light, and the vertical axis represents the absorption coefficient of the solid-state laser medium 20. A higher absorption coefficient indicates a greater amount of light absorption. When the material of the solid-state laser medium 20 is, for example, Nd:YAG, the half-width of the wavelength is very narrow. Therefore, when the wavelength of the pumping light L1 deviates from the half-width specified by the relationship between the wavelength and the absorption coefficient of the solid-state laser medium 20, the amount of absorption of the pumping light L1 in the solid-state laser medium 20 decreases dramatically. As a result, in the solid-state laser resonator 44, the oscillation of the laser light L2 becomes unstable, resulting in a decrease in the output of the pulsed laser light L3.

[0051] Therefore, in this embodiment, the resonator length L of the first resonator 41 ＯＲ１ is the resonator length L of the first resonator 410 according to the comparative example. ＯＲ１ The resonator length L ＯＲ１ The relationship between the cavity length L and the longitudinal mode f can be expressed by the following formula (1). ＯＲ１ As the length of the longitudinal mode f increases, the number of longitudinal modes f within a certain wavelength range increases. In other words, the wavelength difference between multiple longitudinal modes becomes smaller. f = (c / 2nL ＯＲ１ ) × m (1) m: Mode order c: Speed ​​of light n: Refractive index

[0052] 8 is a diagram showing the longitudinal mode characteristics and absorption spectrum of the laser device 1 according to the first embodiment. In this embodiment, the cavity length L is set so that a plurality of longitudinal modes f exist within the full width at half maximum FWHM. ＯＲ１ This allows the resonator length L ＯＲ１ is extended by 0.2%, the wavelength of the longitudinal mode f is shifted by about 0.7 nm in the longer direction. ＯＲ１ is reduced by, for example, 0.2%, the wavelength of the longitudinal mode f shifts by approximately 0.7 nm in the shorter direction. In either case, the wavelength fluctuation width is smaller than in the comparative example, so the shifted wavelength is more likely to fall within the full width at half maximum (FWHM). Therefore, the pumping light L1 generated in the first resonator 41 is efficiently absorbed by the solid-state laser medium 20. As a result, the stability of laser oscillation is improved.

[0053] 9 is a diagram showing an example of the reflection characteristics of the reflective layers 17, 21, and 22 of the laser device 1 according to the first embodiment. In FIG. 9, the horizontal axis represents wavelength, and the vertical axis represents reflectance. As shown in FIG. 9, the reflectance of each reflective layer is designed to be highest at the design wavelength.

[0054] The design wavelength is designed in advance based on the longitudinal mode characteristics of the pumping light L1 and the absorption spectrum of the solid-state laser medium 20. The design wavelength of the reflective layer 17 and the reflective layer 21 is set to 885 nm, which is one of the oscillation wavelengths of the pumping light L1. The reflectance of the reflective layer 22 is designed to be highest at 1030 nm, which is the second design wavelength (oscillation wavelength) of the laser light L2.

[0055] FIG. 10 is a diagram showing an example of the relationship between the light intensity and wavelength of the pump light L1 according to the first embodiment. In FIG. 10, the horizontal axis represents wavelength, and the vertical axis represents light intensity. As described above, the reflectance of the reflective layers 17 and 22 is set to peak at the design wavelength and decrease as the wavelength deviates from the design wavelength. As a result, as shown in FIG. 10, the light intensity of the pump light L1 corresponding to the longitudinal mode f is highest at the design wavelength (885 nm). This encourages the pump light L1 to oscillate at the design wavelength, stabilizing the oscillation of the pump light L1. As a result, the oscillation of the laser light L2 is also stabilized, making it possible to further stabilize the output of the pulsed laser light L3.

[0056] Second Embodiment Fig. 11 is an exploded cross-sectional view of a laser device according to a second embodiment. In Fig. 11, the same components as those in the laser device 1 according to the first embodiment described above are denoted by the same reference numerals, and redundant explanations will be omitted.

[0057] 11, a dielectric substrate 19 is provided in place of the semiconductor substrate 11. The dielectric substrate 19 is made of, for example, a sapphire substrate. In this embodiment, the excitation light L1 passes through the dielectric substrate 19.

[0058] In the laser element 2 according to this embodiment, similarly to the first embodiment, the resonator length L of the first resonator 41 is set so that a plurality of wavelengths of the longitudinal mode of the pumping light L1 are present within the half-width FWHM of the solid-state laser medium 20. ＯＲ１Therefore, even if the oscillation wavelength of the pumping light L1, i.e., the wavelength of the longitudinal mode, shifts due to manufacturing variations in the pumping light source 10 or changes in the environmental temperature, the solid-state laser medium 20 can sufficiently absorb the pumping light L1. This stabilizes the oscillation of the laser light L2, thereby improving the stability of the output of the pulsed laser light L3.

[0059] Similarly to the first embodiment, the reflection characteristics of the reflective layers 17, 21, and 22 are designed so that the reflectivity is highest at the design wavelength. Furthermore, in this embodiment, a dielectric substrate 19 is provided within the first resonator 41. This reduces the amount of absorption of the pumping light L1, making it possible to suppress a decrease in the light intensity of the pumping light L1. This encourages the pumping light L1 to oscillate at the design wavelength, improving the stability of the oscillation of the pumping light L1. As a result, the oscillation of the laser light L2 is also stabilized, further improving the stability of the output of the pulsed laser light L3.

[0060] 12 is an exploded cross-sectional view of a laser device according to a third embodiment. In FIG. 12, the same components as those in the laser device 2 according to the second embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0061] The laser device 3 according to this embodiment includes a saturable absorber 30a instead of the saturable absorber 30. The material of the saturable absorber 30a is different from the material of the saturable absorber 30. The material of the saturable absorber 30 according to the second embodiment is YAG doped with Cr (chromium) (Cr:YAG). On the other hand, the material of the saturable absorber 30a according to this embodiment is spinel (MgAl ２ O ４ ) As with the saturable absorber 30, the saturable absorber 30a functions as a passive Q switch that changes the optical loss due to absorption in accordance with the optical intensity in the solid-state laser resonator 44 and generates pulsed laser light L3. When the material of the saturable absorber 30a is spinel, it can accommodate long wavelengths.

[0062] According to the laser element 3 according to the present embodiment described above, similarly to the second embodiment, the resonator length L of the first resonator 41 is set so that the wavelengths of the plurality of longitudinal modes are within the full width at half maximum FWHM of the solid-state laser medium 20. ＯＲ１ Therefore, even if the wavelength of the longitudinal mode of the pumping light L1 shifts due to manufacturing variations in the pumping light source 10 or changes in the environmental temperature, the solid-state laser medium 20 can sufficiently absorb the pumping light L1. This stabilizes the oscillation of the laser light L2, making it possible to stabilize the output of the pulsed laser light L3.

[0063] 13 is an exploded cross-sectional view of a laser device according to a fourth embodiment. In FIG. 13, the same components as those in the laser device 1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0064] 13, the laser device 4 according to this embodiment newly includes a temperature regulator 23 provided on the solid-state laser medium 20. The temperature regulator 23 is configured by a heater such as an electric heating wire. The temperature of the solid-state laser medium 20 can be adjusted by changing the current flowing through the temperature regulator 23.

[0065] The resonator length L of the second resonator 42 ＯＲ２ (see FIG. 3) can vary with temperature changes of the solid-state laser medium 20. ＯＲ２ The fluctuation of influences the oscillation of the pumping light L1 and the laser light L2.

[0066] Therefore, in this embodiment, the temperature of the solid-state laser medium 20 is adjusted by the temperature adjuster 23, thereby reducing the resonator length L of the second resonator 42. ＯＲ２ This controls the resonator length L ＯＲ２ As a result, the excitation light L1 and the laser light L2 can be oscillated more stably.

[0067] The temperature regulator 23 may be provided in the first resonator 41. In this case, the temperature regulator 23 adjusts the temperature of the first resonator 41, thereby adjusting the resonator length L of the first resonator 41. ＯＲ１ This allows the resonator length L ＯＲ１can be optimized, it becomes possible to oscillate the pump light L1 more stably.

[0068] Furthermore, the temperature adjuster 23 may be provided in both the first resonator 41 and the second resonator 42. In this case, each temperature adjuster 23 adjusts the resonator length L of the first resonator 41. ＯＲ１ and the resonator length L of the second resonator 42 ＯＲ２ This allows the excitation light L1 and the laser light L2 to be oscillated more stably.

[0069] 14 is a diagram showing a laser device according to a fifth embodiment. The laser device 5 shown in FIG. 13 is an example of a multi-beam laser device, and includes a plurality of laser elements 50, a support portion 51, and a drive circuit 52.

[0070] The plurality of laser elements 50 are arranged in a one-dimensional array. Each laser element 50 uses any of the laser elements 1 to 4 described in the first to fourth embodiments. In this embodiment, each laser element 50 can be wrapped in a material with high thermal conductivity, such as a metal sheet (metal foil), and housed in the support section 51.

[0071] The support portion 51 supports the plurality of laser elements 50. The support portion 51 is made of a material with excellent heat resistance, such as a thermosetting resin, ceramics, or metal. However, the support portion 51 may be made of other materials.

[0072] The drive circuit 52 is electrically connected to the plurality of laser elements 50. The drive circuit 52 is configured to supply electrical driving signals to the plurality of laser elements 50. This allows the plurality of laser elements 50 to emit light simultaneously. Note that in the laser device 5 of FIG. 14 , pulsed laser light L3 is emitted in the optical axis direction Z.

[0073] Fig. 15 shows an example of a laser device according to Modification 1. In Fig. 15, components similar to those of the laser device 5 according to the fifth embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

[0074] The laser device 5a according to this modification includes a plurality of laser elements 50, a support portion 51, a plurality of drive circuits 53, and a control circuit 54. In the laser device 5a, an individual drive circuit 53 is provided corresponding to each laser element 50. Each laser element 50 is electrically connected to its corresponding drive circuit 53. Each drive circuit 53 is configured to supply an electrical signal to its corresponding laser element 50.

[0075] The control circuit 54 controls the multiple laser elements 50 via the multiple drive circuits 53. The control circuit 54 is configured to send a control signal to at least one drive circuit 53. For example, the control circuit 54 can control at least one drive circuit 53 to cause the laser element 50 corresponding to the controlled drive circuit 53 to emit light. The control circuit 54 may also control the drive circuits 53 so that some of the multiple laser elements 50 selectively emit light. Furthermore, if the laser element 50 is the laser element 4 according to the fourth embodiment, the control signal sent from the control circuit 54 may include a control signal for the temperature regulator 23. In this case, the drive circuit 53 drives the temperature regulator 23 based on the control signal from the control circuit 54.

[0076] Fig. 16 shows an example of a laser device according to Modification 2. In Fig. 16, components similar to those of the laser device 5 according to the fifth embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

[0077] In the laser device 5b according to this modification, a plurality of laser elements 50 are arranged in a two-dimensional array. The plurality of laser elements 50 are supported by a support portion 55. The plurality of laser elements 50 of the laser device 5b may be connected to a common drive circuit (not shown), as in the laser device 5 (see FIG. 14). Alternatively, the plurality of laser elements 50 of the laser device 5b may be connected to individual drive circuits (not shown), as in the laser device 5a (see FIG. 15).

[0078] The laser devices illustrated in FIGS. 14 to 16 can be applied to multiple fields, including micromachining, lithography, and medicine. In particular, in the field of micromachining, using a laser device with an array of multiple laser elements makes it possible to achieve both high processing precision and high energy output. The arrangement of the multiple laser elements 50 illustrated in FIGS. 14 to 16 is merely an example. Therefore, a laser device may employ an arrangement of the laser elements 50 different from that described above. The multiple laser elements 50 may be periodically arranged in the same row or on the same plane. Furthermore, the multiple laser elements 50 may be arranged on the same plane with different densities depending on the location.

[0079] Modified examples of the laser element according to the present disclosure will be described below.

[0080] Fig. 17 is an exploded cross-sectional view of a laser element according to Modification 1. Fig. 18 is a diagram showing an example of an optical waveform generated by a resonant operation in the laser element shown in Fig. 17. In Figs. 17 and 18, the same components as those in the laser element 1 according to the first embodiment described above are denoted by the same reference numerals, and redundant explanations will be omitted.

[0081] 17 , the laser device 1a according to this modification does not include a saturable absorber 30. Therefore, the second resonator 42 functions as a solid-state laser resonator 44. In the second resonator 42, the excitation light L1 absorbed in the solid-state laser medium 20 undergoes laser oscillation, thereby generating laser light L2. The laser light L2 accumulated in the excitation level of the solid-state laser medium 20 is emitted from the reflective layer 21 as laser light L4.

[0082] The laser element 1a according to this modification does not include the saturable absorber 30 that functions as a passive Q switch. Therefore, the laser light L4 is not pulsed light whose output level alternates between high and low levels, but has a constant output level.

[0083] In the laser element 1a according to this modification, similarly to the first embodiment, the resonator length L of the first resonator 41 is set so that a plurality of wavelengths of the longitudinal mode of the pumping light L1 are present within the half-width FWHM of the solid-state laser medium 20. ＯＲ１Therefore, even if the wavelength of the longitudinal mode of the pumping light L1 shifts due to manufacturing variations in the pumping light source 10 or changes in the environmental temperature, the solid-state laser medium 20 can absorb the pumping light L1 purely. Therefore, the oscillation of the laser light L2 is stabilized, and the output of the laser light L2 can be stabilized.

[0084] The present technology can be configured as follows.

[0085] (1) A laser element comprising: an excitation light source having a first reflection layer with the highest reflectance for excitation light having a first design wavelength; a solid-state laser medium arranged on the excitation light source side in the emission direction of the excitation light; a second reflection layer provided between the excitation light source and the solid-state laser medium, the second reflection layer having the highest reflectance for laser light having a second design wavelength longer than the first design wavelength; and a third reflection layer arranged on the solid-state laser medium side in the emission direction of the laser light, the third reflection layer having the highest reflectance for the excitation light, wherein a distance between the first reflection layer and the third reflection layer is designed so that wavelengths of a plurality of longitudinal modes of the excitation light, including the first design wavelength, are present within a half width of an absorption spectrum of the solid-state laser medium.

[0086] (2) The laser element according to (1), further comprising: a fourth reflective layer disposed on the side of the third reflective layer in the direction in which the laser light is emitted; and a saturable absorber provided between the fourth reflective layer and the third reflective layer.

[0087] (3) The laser element according to (1) or (2), wherein the excitation light source further includes a semiconductor substrate provided between the first reflective layer and the second reflective layer.

[0088] (4) The laser element according to (1) or (2), wherein the excitation light source further includes a dielectric substrate provided between the first reflective layer and the second reflective layer.

[0089] (5) The laser device according to (4), wherein the dielectric substrate is a sapphire substrate.

[0090] (6) The laser element according to (2), wherein the material of the saturable absorber is YAG doped with Cr (chromium).

[0091] (7) The material of the saturable absorber is a spinel (MgAl ２ O ４ ) The laser element according to (2).

[0092] (8) The laser element according to any one of (1) to (7), further comprising a temperature regulator that adjusts the temperature of at least one of the excitation light source and the solid-state laser medium.

[0093] (9) The laser element according to any one of (1) to (8), wherein the excitation light source further includes a fifth reflective layer provided between the first reflective layer and the second reflective layer, and the fifth reflective layer has a higher transmittance of the excitation light than the first reflective layer.

[0094] (10) The laser element according to any one of (1) to (9), wherein the excitation light source further includes an active layer provided between the first reflective layer and the second reflective layer.

[0095] (11) A laser device comprising a plurality of laser elements according to any one of (1) to (10).

[0096] (12) The laser device according to (11), wherein the plurality of laser elements are arranged in a one-dimensional array or a two-dimensional array.

[0097] (13) The laser device according to (11) or (12), further comprising a drive circuit configured to supply an electric signal for driving at least any of the laser elements.

[0098] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0099] 1 to 4, 1a: laser element 5, 5a, 5b: laser device 10: excitation light source 11: semiconductor substrate 13: reflective layer (fifth reflective layer) 15: active layer 17: reflective layer (first reflective layer) 19: dielectric substrate 20: solid-state laser medium 21: reflective layer (third reflective layer) 22: reflective layer (second reflective layer) 23: temperature regulator 30, 30a: saturable absorber 50: laser element 52, 53: drive circuit

Claims

1. A laser element comprising: an excitation light source having a first reflective layer having the highest reflectance for excitation light having a first design wavelength; a solid-state laser medium arranged in the emission direction side of the excitation light source with respect to the excitation light; a second reflective layer provided between the excitation light source and the solid-state laser medium, having the highest reflectance for laser light having a second design wavelength longer than the first design wavelength; and a third reflective layer arranged in the emission direction side of the laser light with respect to the solid-state laser medium, having the highest reflectance for the excitation light, wherein the spacing between the first reflective layer and the second reflective layer is designed so that wavelengths of multiple longitudinal modes of the excitation light including the first design wavelength are present within the half-width of the absorption spectrum of the solid-state laser medium.

2. The laser element described in claim 1, further comprising: a fourth reflective layer arranged on the side of the third reflective layer in the emission direction of the laser light; and a saturable absorber provided between the fourth reflective layer and the third reflective layer.

3. The laser device according to claim 1, wherein the excitation light source further comprises a semiconductor substrate provided between the first reflective layer and the second reflective layer.

4. The laser device according to claim 1, wherein the excitation light source further comprises a dielectric substrate provided between the first reflective layer and the second reflective layer.

5. The laser device according to claim 4, wherein the dielectric substrate is a sapphire substrate.

6. The laser device according to claim 2, wherein the material of the saturable absorber is YAG doped with Cr (chromium).

7. The material of the saturable absorber is Co (cobalt) doped spinel (MgAl ２ O ４ 3. The laser device according to claim 2 .

8. The laser device according to claim 1, further comprising a temperature regulator for adjusting the temperature of at least one of said excitation light source and said solid-state laser medium.

9. The laser element described in claim 1, wherein the excitation light source further has a fifth reflective layer provided between the first reflective layer and the second reflective layer, and the fifth reflective layer has a higher transmittance of the excitation light than the first reflective layer.

10. The laser device according to claim 1, wherein the excitation light source further comprises an active layer provided between the first reflective layer and the second reflective layer.

11. A laser device comprising a plurality of laser elements according to claim 1.

12. The laser device according to claim 11, wherein the plurality of laser elements are arranged in a one-dimensional array or a two-dimensional array.

13. The laser device according to claim 11, further comprising a drive circuit configured to supply a drive electrical signal to at least any of said laser elements.

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