Laser element and laser device

Abstract

[Problem] To provide a laser element capable of stable laser beam output. [Solution] The laser element according to this disclosure includes: an excitation source having a first reflective layer having the highest reflectivity relative to excitation light having a first designed wavelength; a solid-state laser medium disposed on the emission direction side of the excitation light relative to the excitation source; a second reflective layer disposed between the excitation source and the solid-state laser medium and having the highest reflectivity relative to a laser having a second designed wavelength longer than the first designed wavelength; and a third reflective layer disposed on the emission direction side of the laser relative to the solid-state laser medium and having the highest reflectivity relative to the excitation light. The spacing between the first reflective layer and the second reflective layer is designed such that wavelengths including multiple longitudinal modes of the excitation light having the first designed wavelength exist within the FWHM of the absorption spectrum of the solid-state laser medium.

Description

Technical Field

[0001] This disclosure relates to laser elements and laser devices. Background Technology

[0002] Laser technology has been applied in various fields such as micromachining, medical devices, and ranging. In particular, short-pulse laser technology is expected to achieve high-precision machining or high-efficiency wavelength conversion. Peak power exceeding MW can be achieved by using solid-state lasers.

[0003] As described above, laser elements used in laser technology are known to have structures in which the excitation source and a solid-state laser medium are stacked and integrated. This structure allows the laser element to be miniaturized.

[0004] Reference List

[0005] Patent documents

[0006] Patent document 1: WO 2021 / 106757 A Summary of the Invention

[0007] The problem to be solved by the present invention

[0008] In laser elements where the excitation source and solid-state laser medium are integrated, in some cases, the oscillation wavelength of the excitation light shifts due to variations in the resonator length caused by manufacturing changes or changes in the ambient temperature of the excitation source. In such cases, if the optical absorption spectral width of the solid-state laser medium is very small, the excitation light is unlikely to be absorbed by the solid-state laser medium. Therefore, the laser oscillation of the solid-state laser medium is unlikely to be stabilized.

[0009] This disclosure provides a laser element capable of stabilizing the output of a laser beam.

[0010] Solution to the problem

[0011] The laser element of one aspect of this disclosure includes: an excitation source including a first reflective layer having the highest reflectivity relative to an excitation light having a first designed wavelength; a solid-state laser medium disposed on one side relative to the excitation source in the emission direction of the excitation light; a second reflective layer disposed between the excitation source and the solid-state laser medium, the second reflective layer having the highest reflectivity relative to a laser beam having a second designed wavelength longer than the first designed wavelength; and a third reflective layer disposed on one side relative to the solid-state laser medium in the emission direction of the laser beam, the third reflective layer having the highest reflectivity relative to the excitation light. The spacing between the first and second reflective layers is designed such that multiple wavelengths of a longitudinal mode of the excitation light exist within the full width at half maximum (FWHM) of the absorption spectrum of the solid-state laser medium, the multiple wavelengths of the longitudinal mode including the first designed wavelength.

[0012] The laser element may further include: The fourth reflective layer is arranged on one side of the laser beam emission direction relative to the third reflective layer; and A saturable absorber is disposed between the fourth reflective layer and the third reflective layer.

[0013] The excitation light source may further include a semiconductor substrate disposed between the first reflective layer and the second reflective layer.

[0014] The excitation light source may further include a dielectric substrate disposed between the first reflective layer and the second reflective layer.

[0015] The dielectric substrate may include a sapphire substrate.

[0016] The material for saturable absorbers can include chromium (Cr)-doped YAG.

[0017] The material for a saturable absorber may include cobalt (Co)-doped spinel (MgAl2O4).

[0018] The laser element may further include a temperature regulator that adjusts the temperature of at least one of the excitation source and the solid-state laser medium.

[0019] The excitation light source may further include a fifth reflective layer disposed between the first reflective layer and the second reflective layer, and

[0020] The fifth reflective layer may have a higher transmittance of excitation light than the first reflective layer.

[0021] The excitation source may further include an active layer disposed between the first reflective layer and the second reflective layer.

[0022] The laser device in this invention includes a plurality of the laser elements described above.

[0023] Multiple laser elements can be arranged in a one-dimensional array or a two-dimensional array.

[0024] The laser device may further include a driving circuit configured to provide an electrical signal for driving to at least one of a plurality of laser elements. Attached Figure Description

[0025] Figure 1 This is a schematic cross-sectional view of the laser element according to the first embodiment.

[0026] Figure 2 yes Figure 1 The image shows an exploded cross-sectional view of the laser element.

[0027] Figure 3This is a diagram illustrating an example of an optical waveform generated during resonant operation in a laser element according to the first embodiment.

[0028] Figure 4 This is an exploded cross-sectional view of the laser element based on the comparative example.

[0029] Figure 5 This is a diagram illustrating an example of the optical waveform generated during resonant operation in a laser element according to a comparative example.

[0030] Figure 6 This is a diagram illustrating an example of the longitudinal mode characteristics of the excitation light according to a comparative example.

[0031] Figure 7 This is a diagram illustrating an example of the absorption spectrum of a solid-state laser medium.

[0032] Figure 8 This is a diagram showing the longitudinal mode characteristics and absorption spectrum of the laser element according to the first embodiment.

[0033] Figure 9 This is a diagram illustrating an example of the reflective characteristics of the reflective layer of a laser element according to the first embodiment.

[0034] Figure 10 This is a diagram illustrating an example of the relationship between the light intensity and wavelength of the excitation light according to the first embodiment.

[0035] Figure 11 This is an exploded cross-sectional view of the laser element according to the second embodiment.

[0036] Figure 12 This is an exploded cross-sectional view of the laser element according to the third embodiment.

[0037] Figure 13 This is an exploded cross-sectional view of the laser element according to the fourth embodiment.

[0038] Figure 14 This is a diagram showing a laser device according to the fifth embodiment.

[0039] Figure 15 This is a diagram showing an example of a laser device according to Modification 1.

[0040] Figure 16 This is a diagram showing an example of a laser device according to Modification 2.

[0041] Figure 17 It is an exploded cross-sectional view of the laser element based on Modified Example 1.

[0042] Figure 18 It is shown in Figure 17The diagram shows an example of the optical waveform generated during resonant operation in a laser element. Detailed Implementation

[0043] In the following, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that components having substantially the same functional configuration are denoted by the same reference numerals in this document and in the drawings; therefore, repeated descriptions are omitted.

[0044] (First Implementation)

[0045] Figure 1 This is a schematic cross-sectional view of a laser element according to a first embodiment. The laser element 1 according to this embodiment includes an excitation source 10, a solid-state laser medium 20, and a saturable absorber 30. In the laser element 1, the excitation source 10, the solid-state laser medium 20, and the saturable absorber 30 are arranged to be stacked in the optical axis direction (Z-axis direction). The laser element 1 has a generally cylindrical shape. Here, the generally cylindrical shape includes, for example, a generally parallelepiped shape, a generally cylindrical shape, a generally elliptical cylinder shape, a generally triangular prism shape, a generally polygonal prism shape, etc., and the shape of the base is not limited. However, the laser element 1 may have another shape.

[0046] Figure 2 yes Figure 1 An exploded cross-sectional view of laser element 1 is shown in the figure. Figure 2 For the sake of description, the laser element 1 is shown as being divided into an excitation source 10, a solid-state laser medium 20, and a saturable absorber 30. However, the actual laser element 1 may have a structure without gaps between layers, or it may have a structure with gaps between components.

[0047] The excitation light source 10 includes 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.

[0048] The semiconductor substrate 11 is disposed at the end of the excitation light L1 emitted from the excitation light source 10 in the direction of emission. The semiconductor substrate 11 is, for example, an n-type GaAs substrate. However, the semiconductor substrate 11 can be another type of compound semiconductor or silicon semiconductor.

[0049] The contact layer 12 is in contact with the surface on the opposite side of the semiconductor substrate 11 in the emission direction of the excitation light L1. The contact layer 12 comprises, for example, an n-type semiconductor. This n-type semiconductor can be formed by doping silicon with, for example, phosphorus (P) or arsenic (As).

[0050] The reflective layer 13 is in surface contact with the opposite side of the contact layer 12 in the direction of emission of the excitation light L1. The reflective layer 13 is, for example, a distributed Bragg reflector (DBR), in which different semiconductor materials have been alternately stacked to form an optical film thickness of one-quarter wavelength.

[0051] A cladding layer 14 is formed on the surface of the reflective layer 13 on the opposite side in the emission direction of the excitation light L1. Furthermore, an active layer 15 is formed on the surface of the cladding layer 14 on the opposite side in the emission direction of the excitation light L1. Additionally, a cladding layer 16 is formed on the surface of the active layer 15 on the opposite side in the emission direction of the excitation light L1.

[0052] The active layer 15 is formed, for example, by using materials such as InGaN, AlGaN, InGaP, and AlGaInP, which have a smaller band gap and a larger refractive index compared to cladding layers 14 and 16. Furthermore, the active layer 15 may include quantum wells or multiple quantum wells.

[0053] A reflective layer 17 is formed on the surface of the cladding layer 16 on the opposite side of 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 have been alternately stacked with an optical film thickness of one-quarter wavelength. The reflective layer 17 can be formed, for example, from AlAs or AlGaAs. However, the material of the reflective layer 17 is not limited to the materials described above.

[0054] Electrode layer 18 is formed on the surface of the reflective layer 17 on the opposite side of the emission direction of the excitation light L1. Electrode layer 18 is, for example, a P-type semiconductor. This P-type semiconductor can be formed, for example, by doping silicon with boron (B) or aluminum (Al).

[0055] Following the excitation source 10 described above, the solid-state laser medium 20 will be described. The solid-state laser medium 20 comprises a solid material such as yttrium aluminum garnet (YAG) crystal doped with yttrium (Yb) as the laser medium. In this case, the oscillation wavelength of the solid-state laser medium 20 is 1030 nm. For example, as the laser medium of the solid-state laser medium 20, at least any material selected from 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, or YB:YAB can be used. The solid-state laser medium 20 can be a quaternary laser medium or a tertiary laser medium.

[0056] A reflective layer 21 (third reflective layer) is formed on the surface of the solid-state laser medium 20 on the side facing the emission direction of the laser beam L2. Furthermore, a reflective layer 22 (second reflective layer) is formed on the surface facing the excitation source of the solid-state laser medium 20. The reflective layer 21 is a high reflector (HR) with high reflectivity relative to the first designed 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 and reflects the laser beam L2.

[0057] Following the description of the solid-state laser medium 20, the saturable absorber 30 will be described. The saturable absorber 30 is a passive Q-switching element. The saturable absorber 30 comprises, for example, a chromium (Cr)-doped YAG (Cr:YAG) crystal. The saturable absorber 30 exhibits saturable absorption characteristics relative to the intensity of the laser beam L2 passing through it. Furthermore, V:YAG can also be used as the saturable absorber of the saturable absorber 30. However, another type of saturable absorber can be used as the saturable absorber 30. Additionally, an active Q-switching element can be used as the saturable absorber 30.

[0058] A reflective layer 31 (fourth reflective layer) is disposed on the surface of the saturable absorber 30 on the side of the emission direction of the laser beam L2. The reflective layer 31 reflects the laser beam L2. It should be noted that the reflective layer 31 may be a semi-transparent layer that is part of the transmitted laser beam L2.

[0059] In the laser element 1 configured as described above, the first resonator 41 is formed from components from the reflective layer 17 to the reflective layer 22. Furthermore, the second resonator 42 is formed from the reflective layer 22, the solid-state laser medium 20, and the reflective layer 21. The first resonator 41 and the second resonator 42 constitute an excitation light resonator 43. The excitation light resonator 43 can resonate with electromagnetic waves having a wavelength of, for example, 885 nm.

[0060] Furthermore, in the laser element 1 according to this embodiment, the solid-state laser resonator 44 is formed from components from the reflective layer 22 to the reflective layer 31. The solid-state laser resonator 44 can resonate with electromagnetic waves having a wavelength of, for example, 1030 nm.

[0061] Note that in the laser element 1 according to this embodiment, in order to prevent the excitation light L1 from oscillating between the reflective layer 17 and the reflective layer 13, it is desirable that the reflectivity of the reflective layer 13 is lower than that of the reflective layer 17, at least relative to electromagnetic waves having a designed wavelength. In other words, it is desirable that the transmittance of the excitation light L1 in the reflective layer 13 is higher than that in the reflective layer 17.

[0062] Next, we will refer to Figure 2 and Figure 3 Describe the operation of laser element 1.

[0063] Figure 3This is a diagram illustrating an example of the optical waveform generated during resonant operation in the laser element 1 according to the first embodiment. In this embodiment, the resonator length L of the first resonator 41 has been designed based on 885 nm as the design wavelength. OR1 That is, the spacing between reflective layer 17 and reflective layer 12. Therefore, the 885-nm wavelength component of the self-emitted light forms a standing wave between reflective layer 17 and reflective layer 21, and is amplified by active layer 15.

[0064] A solid-state laser medium 20 exists in the optical path of the excitation light L1. The optical absorption wavelength band of the solid-state laser medium 20 includes the first design wavelength (oscillation wavelength) of 885 nm for the excitation light L1. Therefore, the solid-state laser medium 20 is excited, and a total inversion is formed within it. The excitation light L1 is amplified due to stimulated emission, and thus, the excitation resonator 43 oscillates with a wavelength of 885 nm.

[0065] A portion of the light that has passed through the excitation resonator 43 of the reflective layer 21 enters the saturable absorber 30 in the solid-state laser resonator 44. The light that has entered begins to oscillate back and forth in the solid-state laser resonator 44, which includes the solid-state laser medium 20 and the saturable absorber 30. If the light intensity has increased, the saturable absorber 30 absorbs the light and excites electrons at the ground level, thus temporarily preventing oscillation in the solid-state laser resonator 44. In the solid-state laser medium 20, stimulated emission is prevented, and the number of electrons in the excited energy level increases. After a certain period of time, the excitation level of the saturable absorber 30 is filled with electrons, and the light absorption rate of the saturable absorber 30 decreases. Excitation emission occurs in the solid-state laser medium 20, and the solid-state laser resonator 44 performs laser oscillation at a wavelength of 1030 nm. At this time, the energy accumulated in the excited energy level of the solid-state laser medium 20 is emitted as a pulsed laser beam L3 from the reflective layer 31 to the outside of the laser element 1.

[0066] If the pulsed laser beam L3 has been emitted, the light intensity in the solid-state laser resonator 44 decreases. Therefore, there is room for the excitation level of the saturable absorber 30, and the light absorption rate of the saturable absorber 30 increases again. Excitation light L1, which has already passed through the reflective layer 21, is continuously supplied to the solid-state laser resonator 44 from the excitation light resonator 43. Therefore, the light intensity in the solid-state laser resonator 44 increases again, and the above process repeats. Therefore, the laser element 1 repeatedly emits the pulsed laser beam L3.

[0067] As described above, the saturable absorber 30 functions as a passive Q-switch, which changes the optical loss caused by absorption according to the light intensity in the resonator and generates a pulsed laser beam 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 duration of the generated pulsed laser beam L3. On the other hand, the pulse duration is proportional to the resonator length of the solid-state laser resonator 44.

[0068] Here, a laser element 100 will be described in comparison with the laser element 1 according to the first embodiment described above.

[0069] Figure 4 This is an exploded cross-sectional view based on the laser element 100 of the comparative example. Figure 4 In this text, components similar to those of the laser element 1 according to the first embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted. Figure 4 In the laser element 100 shown, the first resonator 410 includes components from the reflective layer 17 to the reflective layer 13. Furthermore, the second resonator 420 includes components from the reflective layer 13 to the reflective layer 22.

[0070] Figure 5 This is a diagram illustrating an example of the optical waveform generated during resonant operation in the laser element 100 according to the comparative example. (See diagram for example.) Figure 5 As shown, the resonator length L of the first resonator 410 according to this comparative example OR1 The resonator length L is smaller than that of the first resonator 41 according to the first embodiment. OR1 .

[0071] Figure 6 This is a diagram illustrating an example of the longitudinal mode characteristics of the excitation light L1 according to the comparative example. Figure 6 In the diagram, the horizontal axis represents the wavelength of light, and the vertical axis represents the intensity of light. Here, the vertical mode represents the frequency at which the excitation light L1 can be generated by the resonance of the first resonator 410 (or the first resonator 41). In this comparative example, the number of vertical modes present within a specific wavelength range depends on the resonator length L of the first resonator 410. OR1 .exist Figure 6 In the example shown, the resonator length L of the first resonator 41 has been designed in such a way that... OR1 That is, the longitudinal mode occurs at a wavelength of 885 nm.

[0072] However, if the film thickness changes when the components in the first resonator 410 are formed by epitaxial growth of a semiconductor material, or if the ambient temperature of the excitation light source 10 changes, the resonator length L will increase due to the expansion and contraction of the semiconductor material and the change in its refractive index. OR1 It can change. For example, as Figure 6 As shown, if the resonator length L OR1 An increase of 0.2% in some cases causes the longitudinal mode of the excitation light L1 to shift in a direction with a length of approximately 2 nm. Furthermore, if the resonator length L... OR1 A 0.2% reduction in intensity, in some cases, shifts the longitudinal mode of the excitation light L1 in a direction approximately 2 nm shorter.

[0073] Figure 7 This is a diagram illustrating an example of the absorption spectrum of a solid-state laser medium 20. Figure 7 In the diagram, 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 greater light absorption. In the case where the material of the solid-state laser medium 20 is, for example, Nd:YAG, the full width at half maximum (FWHM) of the wavelength is very small. Therefore, if the wavelength of the excitation light L1 deviates from the FWHM specified by the relationship between the wavelength and absorption coefficient of the solid-state laser medium 20, the absorption of the excitation light L1 by the solid-state laser medium 20 decreases sharply. Consequently, in the solid-state laser resonator 44, the oscillation of the laser beam L2 becomes unstable, and the output of the pulsed laser beam L3 decreases.

[0074] In view of the above, in this embodiment, according to the comparative example, the resonator length L of the first resonator 41 is... OR1 The resonator length L is designed to be greater than that of the first resonator 410. OR1 Resonator length L OR1 The relationship between the resonator length L and the longitudinal mode f can be expressed by formula (1) as described below. According to formula (1), if the resonator length L OR1 Increasing the number of longitudinal modes f within a specific wavelength range increases the number of longitudinal modes f. In other words, the wavelength difference between multiple longitudinal modes decreases.

[0075] f = (c / 2nL OR1 ) × m (1)

[0076] m: Pattern order

[0077] c: speed of light

[0078] n: Refractive index

[0079] Figure 8 This is a diagram showing the longitudinal mode characteristics and absorption spectrum of the laser element 1 according to the first embodiment. In this embodiment, the resonator length L has been designed in such a way that... OR1 That is, multiple longitudinal modes f exist within the full width at half maximum (FWHM). Therefore, for example, in the resonator length L... OR1 With an increase of 0.2%, the wavelength of the longitudinal mode f shifts in a direction approximately 0.7 nm longer. Conversely, with a resonator length L...OR1 When the wavelength is reduced by, for example, 0.2%, the wavelength of the longitudinal mode f shifts in a direction approximately 0.7 nm shorter. In either case, the range of this wavelength variation is smaller than that in the comparative example, and therefore there is a high probability that the shifted wavelength will fall within the full width at half maximum (FWHM). Consequently, the excitation light L1 generated by the first resonator 41 is effectively absorbed by the solid-state laser medium 20. As a result, the stability of the laser oscillation is improved.

[0080] Figure 9 This is a diagram illustrating an example of the reflection characteristics of the reflective layers 17, 21, and 22 of the laser element 1 according to the first embodiment. Figure 9 In the diagram, the horizontal axis represents wavelength, and the vertical axis represents reflectivity. For example... Figure 9 As shown, the reflectivity of each reflective layer has been designed to be the highest at the design wavelength.

[0081] The design wavelength has been pre-designed based on the longitudinal mode characteristics of the excitation light L1 and the absorption spectrum of the solid-state laser medium 20. The design wavelengths of the reflective layers 17 and 21 are set to 885 nm, which is an example of the oscillation wavelength of the excitation light L1. The reflectivity of the reflective layer 22 has been designed to be highest at 1030 nm, which is the second design wavelength (oscillation wavelength) of the laser beam L2.

[0082] Figure 10 This is a diagram illustrating an example of the relationship between the intensity and wavelength of the excitation light L1 according to the first embodiment. Figure 10 In the diagram, the horizontal axis represents wavelength, and the vertical axis represents light intensity. As described above, the reflectivity of reflective layer 17 and reflective layer 22 has been set to peak at the design wavelength and decrease with increasing deviation from the design wavelength. As a result, as... Figure 10 As shown, the light intensity of the excitation light L1 corresponding to the longitudinal mode f is highest at the designed wavelength (885 nm). Therefore, the excitation light L1 is induced to oscillate at the designed wavelength, and thus the oscillation of the excitation light L1 is stabilized. Consequently, the oscillation of the laser beam L2 is also stabilized, and the output of the pulsed laser L3 is further stabilized.

[0083] (Second Implementation)

[0084] Figure 11 This is an exploded cross-sectional view of the laser element according to the second embodiment. Figure 11 In this document, components similar to those of the laser element 1 according to the first embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0085] exist Figure 11In the laser element 2 shown, a dielectric substrate 19 is provided instead of a semiconductor substrate 11. The dielectric substrate 19 includes, for example, a sapphire substrate. In this embodiment, the excitation light L1 passes through the dielectric substrate 19.

[0086] In the laser element 2 according to this embodiment, similar to the first embodiment, the resonator length L of the first resonator 41 has been designed in such a way that... OR1 Multiple wavelengths of the longitudinal mode of excitation light L1 exist within the full width at half maximum (FWHM) of the solid-state laser medium 20. Therefore, even if the oscillation wavelength of excitation light L1 (i.e., the wavelength of the longitudinal mode) shifts due to variations in the manufacturing of the excitation source 10 or changes in ambient temperature, the solid-state laser medium 20 can still adequately absorb excitation light L1. Consequently, the oscillation of laser L2 is stabilized, and the output stability of pulsed laser L3 is improved.

[0087] Furthermore, similar to the first embodiment, the reflective characteristics of reflective layers 17, 21, and 22 are designed to maximize reflectivity at the designed wavelength. Additionally, in this embodiment, the dielectric substrate 19 is disposed within the first resonator 41. Therefore, the absorption of the excitation light L1 is reduced, and thus, a decrease in the intensity of the excitation light L1 can be prevented. Consequently, the excitation light L1 is induced to oscillate at the designed wavelength, and thus the stability of the oscillation of the excitation light L1 is improved. Consequently, the oscillation of the laser beam L2 is also stabilized, and the stability of the output of the pulsed laser L3 is further improved.

[0088] (Third implementation method)

[0089] Figure 12 This is an exploded cross-sectional view of the laser element according to the third embodiment. Figure 12 In this document, components similar to those of the laser element 2 according to the second embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0090] The laser element 3 according to this embodiment includes a saturable absorber 30a instead of a saturable absorber 30. The material of the saturable absorber 30a is different from that of the saturable absorber 30. The material of the saturable absorber 30 according to the second embodiment is chromium (Cr)-doped YAG (Cr:YAG). On the other hand, the material of the saturable absorber 30a according to this embodiment is cobalt (Co)-doped spinel (MgAl2O4). Similar to the saturable absorber 30, the saturable absorber 30a functions as a passive Q-switch, which changes the optical loss caused by absorption according to the light intensity in the solid-state laser resonator 44 and generates a pulsed laser beam L3. When the material of the saturable absorber 30a is spinel, long wavelengths can be processed.

[0091] By employing the laser element 3 according to the present embodiment described above, similar to the second embodiment, the resonator length L of the first resonator 41 has been designed in such a manner that... OR1 That is, multiple longitudinal mode wavelengths exist within the full width at half maximum (FWHM) of the solid-state laser medium 20. Therefore, even if the wavelength of the longitudinal mode of the excitation light L1 shifts due to manufacturing variations of the excitation source 10 or changes in ambient temperature, the solid-state laser medium 20 can still adequately absorb the excitation light L1. Consequently, the oscillation of laser L2 is stabilized, thus enabling stable output of pulsed laser L3.

[0092] (Fourth Implementation)

[0093] Figure 13 This is an exploded cross-sectional view of the laser element according to the fourth embodiment. Figure 13 In this document, components similar to those of the laser element 1 according to the first embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0094] like Figure 13 As shown, the laser element 4 according to this embodiment newly includes a temperature regulator 23 disposed in the solid-state laser medium 20. The temperature regulator 23 has a heater such as a heating wire. The temperature of the solid-state laser medium 20 can be adjusted by changing the current flowing through the temperature regulator 23.

[0095] The resonator length L of the second resonator 42 OR2 (See) Figure 3 The resonator length L can vary depending on the temperature of the solid-state laser medium 20. OR2 The changes affect the oscillation of the excitation light L1 and the laser beam L2.

[0096] In view of the above, in this embodiment, the resonator length L of the second resonator 42 is controlled by adjusting the temperature of the solid-state laser medium 20 using the temperature regulator 23. OR2 Therefore, the resonator length L can be optimized. OR2 As a result, the excitation light L1 and the laser beam L2 can oscillate more stably.

[0097] It is worth noting that the temperature regulating unit 23 can also be provided in the first resonator 41. In this case, by adjusting the temperature of the first resonator 41 using the temperature regulating unit 23, the resonator length L of the first resonator 41 can be controlled. OR1 Therefore, the resonator length L can be optimized. OR1 This allows the excitation light L1 to oscillate more stably.

[0098] Furthermore, a temperature regulator 23 can be disposed in the first resonator 41 and the second resonator 42. In this case, the resonator length L of the first resonator 41 can be optimized by using the appropriate temperature regulator 23. OR1 The resonator length L of the second resonator 42 OR2 Therefore, the excitation light L1 and the laser beam L2 can oscillate more stably.

[0099] (Fifth Implementation)

[0100] Figure 14 This is a diagram showing a laser device according to the fifth embodiment. Figure 13 The laser device 5 shown is an example of a multi-beam laser device and includes multiple laser elements 50, a support 51, and a drive circuit 52.

[0101] Multiple laser elements 50 are arranged in a one-dimensional array. For each laser element 50, any one of the laser elements 1 to 4 described in the first to fourth embodiments above is used. Furthermore, in this embodiment, the outer periphery of each laser element 50 may be wrapped with a material with high thermal conductivity (such as a metal sheet (metal foil)) and may be housed in a support member 51.

[0102] The support 51 supports multiple laser elements 50. The support 51 is formed using materials with excellent heat resistance, such as thermosetting resin, ceramic, or metal. However, the support 51 can be formed using other materials.

[0103] A drive circuit 52 is electrically connected to multiple laser elements 50. The drive circuit 52 is configured to provide electrical signals for driving the multiple laser elements 50. Therefore, the multiple laser elements 50 can emit light simultaneously. It should be noted that... Figure 14 In the laser device 5, the pulsed laser beam L3 is emitted in the optical axis direction Z.

[0104] Figure 15 An example of a laser device according to Modification 1 is shown. Figure 15 In this document, components similar to those of the laser device 5 according to the fifth embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0105] The laser device 5a according to this modification includes a plurality of laser elements 50, a support member 51, a plurality of drive circuits 53, and a control circuit 54. In the laser device 5a, a separate drive circuit 53 corresponding to each laser element 50 is provided. Furthermore, each laser element 50 is electrically connected to its corresponding drive circuit 53. Each drive circuit 53 is configured to provide an electrical signal to its corresponding laser element 50.

[0106] The control circuit 54 controls a plurality of laser elements 50 via a plurality of drive circuits 53. The control circuit 54 is configured to transmit control signals to at least one drive circuit 53. For example, the control circuit 54 may control at least one drive circuit 53 to cause the laser element 50 corresponding to the controlled drive circuit 53 to emit light. Furthermore, the control circuit 54 may control the drive circuits 53 such that some of the plurality of laser elements 50 selectively emit light. Additionally, 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.

[0107] Figure 16 An example of a laser device according to Modification 2 is shown. Figure 16 In this document, components similar to those of the laser device 5 according to the fifth embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0108] 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 member 55. As in the laser device 5 (see...) Figure 14 The multiple laser elements 50 of laser device 5b can be connected to a common drive circuit (not shown). Alternatively, the multiple laser elements 50 of laser device 5b can be connected to separate drive circuits (not shown), as in laser device 5a (see...). Figure 15 ).

[0109] Figures 14 to 16 The laser device shown can be applied to various fields such as micromachining, photolithography, and medical care. In particular, in the field of micromachining, both high processing precision and high energy output can be achieved by using a laser device in which multiple laser elements are arranged. It should be noted that... Figures 14 to 16 The example of the arrangement of the plurality of laser elements 50 shown is merely exemplary. Therefore, the laser device may employ an arrangement different from that described above. The plurality of laser elements 50 may be arranged periodically in the same row or in the same plane. Furthermore, the plurality of laser elements 50 may be arranged at different densities depending on their positions on the same plane.

[0110] In the following text, variations of the laser element according to this disclosure will be described.

[0111] Figure 17 It is an exploded cross-sectional view of the laser element based on Modified Example 1. Figure 18 It is shown in Figure 17 The diagram illustrates an example of the optical waveform generated during resonant operation in a laser element. Figure 17 and Figure 18 In this document, components similar to those of the laser element 1 according to the first embodiment described above are indicated by the same reference numerals, and repeated descriptions will be omitted.

[0112] like Figure 17 As shown, the laser element 1a according to this modification does not have a saturable absorber 30. Therefore, the second resonator 42 is used as a solid-state laser resonator 44. In the second resonator 42, the excitation light L1 absorbed by the solid-state laser medium 20 performs laser oscillation to generate a laser beam L2. The laser beam L2 accumulated in the excitation energy level of the solid-state laser medium 20 is emitted from the reflective layer 21 as a laser beam L4.

[0113] According to this modification, the laser element 1a is not equipped with a saturable absorber 30 used as a passive Q-switch. Therefore, the laser beam L4 is not a pulsed light with an output level alternating between high and low levels, but has a constant output level.

[0114] In the laser element 1a according to this modification, similar to the first embodiment, the resonator length L of the first resonator 41 has been designed in such a way that... OR1 Multiple wavelengths of the longitudinal mode of excitation light L1 exist within the full width at half maximum (FWHM) of the solid-state laser medium 20. Therefore, even if the wavelengths of the longitudinal mode of excitation light L1 have shifted due to variations in the manufacturing of the excitation source 10 or changes in ambient temperature, the solid-state laser medium 20 can still absorb excitation light L1 into the pure light. Consequently, the oscillation of laser L2 is stabilized, thus enabling the output of laser L2 to be stabilized.

[0115] It should be noted that this technology may also have the following configurations.

[0116] (1) A laser element, comprising: An excitation light source, comprising a first reflective layer having the highest reflectivity relative to excitation light having a first designed wavelength; The solid-state laser medium is positioned on one side of the excitation light emission direction relative to the excitation source. A second reflective layer is disposed between the excitation source and the solid-state laser medium. The second reflective layer has the highest reflectivity relative to a laser beam having a second design wavelength longer than the first design wavelength. The third reflective layer, positioned on one side of the laser beam emission direction relative to the solid-state laser medium, has the highest reflectivity relative to the excitation light. The spacing between the first reflective layer and the third reflective layer is designed such that multiple wavelengths of the longitudinal mode of the excitation light exist within the full width at half maximum (FWHM) of the absorption spectrum of the solid-state laser medium, and the multiple wavelengths of the longitudinal mode include the first designed wavelength.

[0117] (2) The laser element according to (1) further includes: The fourth reflective layer is arranged on one side of the laser beam emission direction relative to the third reflective layer; and A saturable absorber is positioned between the fourth and third reflective layers.

[0118] (3) The laser element according to (1) or (2), wherein the excitation source further includes a semiconductor substrate disposed between the first reflective layer and the second reflective layer.

[0119] (4) The laser element according to (1) or (2), wherein the excitation source further includes a dielectric substrate disposed between the first reflective layer and the second reflective layer.

[0120] (5) The laser element according to (4), wherein the dielectric substrate includes a sapphire substrate.

[0121] (6) The laser element according to (2), wherein the material of the saturable absorber includes YAG doped with chromium (Cr).

[0122] (7) The laser element according to (2), wherein the material of the saturable absorber includes cobalt (Co) doped spinel (MgAl2O4).

[0123] (8) The laser element according to any one of (1) to (7) further includes a temperature regulator for adjusting the temperature of at least one of the excitation source and the solid-state laser medium.

[0124] (9) A laser element based on any one of (1) to (8), The excitation light source further includes a fifth reflective layer, which is disposed between the first reflective layer and the second reflective layer. The transmittance of the excitation light from the fifth reflective layer is higher than that from the excitation light from the first reflective layer.

[0125] (10) A laser element according to any one of (1) to (9), wherein the excitation source further includes an active layer disposed between the first reflective layer and the second reflective layer.

[0126] (11) A laser device, comprising: Multiple laser elements according to any one of (1) to (10).

[0127] (12) The laser device according to (11), wherein multiple laser elements are arranged in a one-dimensional array or a two-dimensional array.

[0128] (13) The laser device according to (11) or (12) further includes a driving circuit configured to provide an electrical signal for driving to at least one of the plurality of laser elements.

[0129] This disclosure is not limited to the various embodiments described above, but 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 in the claims and their equivalents.

[0130] Reference Symbol List

[0131] 1-4, 1a Laser element

[0132] 5, 5a, 5b Laser devices

[0133] 10 Excitation Light Source

[0134] 11 Semiconductor substrate

[0135] 13. Reflective layer (fifth reflective layer)

[0136] 15. Active Layer

[0137] 17. Reflective layer (first reflective layer)

[0138] 19 Dielectric substrates

[0139] 20 Solid-state laser media

[0140] 21. Reflective layer (third reflective layer)

[0141] 22. Reflective layer (second reflective layer)

[0142] 23 Temperature Regulator

[0143] 30, 30a saturable absorbers

[0144] 50 laser components

[0145] 52, 53 drive circuits

Claims

1. A laser element, comprising: An excitation light source, the excitation light source including a first reflective layer having the highest reflectivity relative to excitation light having a first designed wavelength; A solid-state laser medium is disposed on one side of the excitation light emission direction relative to the excitation light source; A second reflective layer is disposed between the excitation source and the solid-state laser medium, and the second reflective layer has the highest reflectivity relative to a laser beam having a second design wavelength that is longer than the first design wavelength; as well as A third reflective layer is disposed on one side of the laser beam emission direction relative to the solid-state laser medium, and this third reflective layer has the highest reflectivity relative to the excitation light. The spacing between the first reflective layer and the second reflective layer is designed such that multiple wavelengths of the longitudinal mode of the excitation light exist within the full width at half maximum (FWHM) of the absorption spectrum of the solid-state laser medium, and the multiple wavelengths of the longitudinal mode include the first designed wavelength.

2. The laser element according to claim 1, further comprising: A fourth reflective layer is disposed on one side of the emission direction of the laser beam relative to the third reflective layer; as well as A saturable absorber is disposed between the fourth reflective layer and the third reflective layer.

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

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

5. The laser element according to claim 4, wherein, The dielectric substrate includes a sapphire substrate.

6. The laser element according to claim 2, wherein, The material of the saturable absorber includes chromium (Cr)-doped YAG.

7. The laser element according to claim 2, wherein, The material of the saturable absorber includes cobalt (Co)-doped spinel (MgAl2O4).

8. The laser element according to claim 1, further comprising: A temperature regulator that adjusts the temperature of at least one of the excitation source and the solid-state laser medium.

9. The laser element according to claim 1, in, The excitation light source further includes a fifth reflective layer, which is disposed between the first reflective layer and the second reflective layer. The transmittance of the excitation light from the fifth reflective layer is higher than that of the excitation light from the first reflective layer.

10. The laser element according to claim 1, wherein, The excitation light source further includes an active layer disposed between the first reflective layer and the second reflective layer.

11. A laser device, comprising: Multiple 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: The driving circuit is configured to provide an electrical signal for driving to at least one of the plurality of laser elements.

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