A three-wavelength common-cavity straight-cavity Nd:YAG-LBO frequency-doubling solid laser

Abstract

The application discloses a three-wavelength common-cavity straight-cavity Nd:YAG-LBO frequency-doubling solid laser. The solid laser comprises an 808nm pumping source system, a focusing mirror, a Nd:YAG gain crystal, an ultrathin fused quartz phase homogenizing sheet, an LBO nonlinear frequency-doubling crystal and an output coupling mirror arranged along an optical axis in sequence, the focusing mirror and the output coupling mirror are respectively coated with three-wavelength composite films which are transparent to 808nm, totally reflective to 1112nm, 1116nm and 1122nm infrared fundamental waves and totally transparent to 556nm, 558nm and 561nm yellow light, and a double-body partition independent temperature control system for independently controlling the temperature of the gain crystal and the frequency-doubling crystal is arranged. The single resonant cavity of the application synchronously outputs three coaxial and same-direction yellow light lasers, replaces a combination scheme of multiple independent single-wavelength lasers, and has the advantages of compact structure and stable output.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state laser technology, specifically to a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser. Background Technology

[0002] In applications such as biological fluorescence microscopy excitation, visible light spectrometer wavelength calibration, differential interferometry detection, and environmental multi-component gas absorption detection, it is often necessary to simultaneously cover the three yellow light bands of 556nm, 558nm, and 561nm. Currently, the industry typically uses a combination of three independent single-wavelength yellow light lasers, resulting in a large system size, complex optical path calibration steps, and high costs. Conventional 561nm direct-cavity frequency-doubled lasers are designed to oscillate only on a single 1122nm fundamental spectral line. The intracavity Nd:YAG crystal naturally contains multiple near-infrared transition lines at 1112nm, 1116nm, and 1122nm. Existing solutions suppress the two redundant spectral lines at 1112nm and 1116nm by adding etalons, narrowband coatings, and filters. When these two suppressed spectral lines spontaneously oscillate, they generate parasitic clutter peaks at 556nm and 558nm, which are usually regarded as harmful noise and eliminated in the industry, leading to wasted gain, structural complexity, and increased production costs.

[0003] Furthermore, conventional straight-cavity lasers suffer from multi-mode random oscillation, with random fluctuations in subpeak intensity and wavelength drift, resulting in poor output stability and making it impossible to achieve controllable synchronous output of three wavelengths. Even when attempting multi-wavelength oscillation within the same resonant cavity, the difference in gain coefficients among the spectral lines means that a single spectral line tends to oscillate preferentially and suppress the others, further complicating the challenge of synchronous multi-wavelength output.

[0004] Therefore, developing a compact, monolithic Nd:YAG crystal single-resonant-cavity all-solid-state laser capable of achieving efficient, synchronous, and stable output of three wavelengths around 561nm, overcoming mode competition, and exhibiting high output efficiency and strong stability has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This application provides a three-wavelength common-cavity direct-cavity Nd:YAG-LBO frequency-doubled solid-state laser, which at least solves the problems of existing technologies where multiple wavelength light sources require multiple lasers to be combined, resulting in large system size and high cost; conventional single-wavelength lasers suppressing redundant spectral lines, causing gain waste and structural complexity; and multi-longitudinal-mode random oscillations leading to poor output stability.

[0006] This application provides a three-wavelength common-cavity direct-cavity Nd:YAG-LBO frequency-doubled solid-state laser, including a pump source system, a focusing mirror, an Nd:YAG gain crystal, an LBO nonlinear frequency-doubled crystal, and an output coupling mirror arranged sequentially along the optical axis. The pump source system is an 808nm semiconductor laser end-face pump, and further includes: An ultrathin fused silica phase homogenizer is disposed between the Nd:YAG gain crystal and the LBO nonlinear frequency doubling crystal; The dual-body zoned independent temperature control system includes at least a first temperature control heat sink, a second temperature control heat sink, and an integrated micro-vibration damping temperature control base. The first temperature control heat sink is paired with the Nd:YAG gain crystal, and the second temperature control heat sink is paired with the LBO nonlinear frequency doubling crystal. The focusing lens and the output coupling lens are each coated with a three-wavelength composite film. The three-wavelength composite film is anti-reflective for 808nm, totally reflective for 1112nm, 1116nm, and 1122nm infrared fundamental frequencies, and totally transmittable for 556nm, 558nm, and 561nm yellow light. The 808nm pump light from the pump source system is coupled to the Nd:YAG gain crystal via the focusing lens. The resulting 1112nm, 1116nm, and 1122nm infrared fundamental frequency light is frequency-doubled in the resonant cavity by the LBO nonlinear frequency doubling crystal and converted into 556nm, 558nm, and 561nm yellow light, which is then output by the output coupling lens.

[0007] Optionally, the ultrathin fused silica phase homogenizer uses the wavelength difference of the three fundamental frequency lights to introduce an optical path difference to finely adjust the optical field distribution in the cavity, so that the output power ratio of the three yellow lights of 556nm, 558nm and 561nm can be continuously adjusted in the range of 1:0.8~1.2:1~1.5.

[0008] Optionally, the temperature control accuracy of the first temperature-controlled heat sink is ±0.05℃, which is used to adjust the energy level gain distribution of the Nd:YAG gain crystal by adjusting the temperature, so that the gain coefficients of the three spectral lines of 1112nm, 1116nm and 1122nm are nearly matched.

[0009] Optionally, the doping concentration of the Nd:YAG gain crystal is 0.5 at.% to 1.5 at.%.

[0010] Optionally, the LBO nonlinear frequency doubling crystal is a crystal that satisfies type I phase matching, and its crystal size is 3mm×3mm×12mm.

[0011] Optionally, in the three-wavelength composite film: The transmittance of the 808nm antireflection coating is greater than 95%; The reflectivity R of the high-reflectivity film for the 1112nm, 1116nm, and 1122nm infrared fundamental frequencies is greater than 99.5%; The transmittance of the fully transparent film for 556nm, 558nm, and 561nm yellow light is greater than 92%.

[0012] Optionally, the resonant cavity is a linear flat-flat cavity structure with a cavity length of 85–110 mm.

[0013] Optionally, the Nd:YAG gain crystal has a crystal size of 3mm × 3mm × 8mm.

[0014] Optionally, the maximum output pump power of the pump source system is 5W to 10W.

[0015] Optionally, it also includes a rear beam shaping component, which includes a diverging lens and a converging lens arranged sequentially along the output optical path. The focal length ratio of the diverging lens and the converging lens is within 1.2 to 1.9, and both sides of the diverging lens and the converging lens are coated with a three-way yellow light anti-reflection coating.

[0016] Compared with related technologies, the three-wavelength common-cavity direct-cavity Nd:YAG-LBO frequency-doubled solid-state laser provided in this application has at least the following technical advantages: By depositing three-wavelength composite films on both the focusing lens and the output coupling lens, the 808nm pump light is transmitted into the resonant cavity while the three infrared fundamental frequency beams of 1112nm, 1116nm, and 1122nm are totally reflected and retained in the cavity for continuous oscillation. An ultrathin fused silica phase homogenizer placed between the Nd:YAG gain crystal and the LBO nonlinear frequency doubling crystal introduces an optical path difference by utilizing the wavelength difference between the three fundamental frequency beams, balancing the gain competition of the three spectral lines and preventing one spectral line from oscillating preferentially while suppressing the other two. The dual-body zoned independent temperature control system independently adjusts the temperature of the Nd:YAG gain crystal through the first temperature-controlled heat sink to match the gain coefficients of the three spectral lines, and independently adjusts the phase matching temperature of the LBO nonlinear frequency doubling crystal through the second temperature-controlled heat sink to simultaneously meet the Type I phase matching conditions of the three wavelengths. The three systems work together to ensure that the three infrared fundamental frequency beams oscillate stably and synchronously in the same linear flat-flat cavity.

[0017] In summary, under the influence of the intracavity reciprocating optical field, the three fundamental frequency beams are synchronously frequency-doubled intracavity via an LBO nonlinear frequency-doubled crystal, converting them into three yellow beams of 556nm, 558nm, and 561nm, which are then output coaxially and in the same direction by the fully transparent film of the output coupling mirror. This single resonant cavity replaces the combination of three independent single-wavelength lasers, eliminating the need for multiple pump sources, resonant cavities, and optical adjustment frames, and removing the optical path calibration steps required for using multiple lasers in combination. The structure is compact and the output is stable.

[0018] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0019] Figure 1 This is a perspective view of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser according to an exemplary embodiment.

[0020] Figure 2 This is a cross-sectional view of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser according to an exemplary embodiment.

[0021] Figure 3 This is an optical path diagram of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser, according to an exemplary embodiment.

[0022] Explanation of reference numerals in the attached figures: Pumping and focusing components: 1-Pump source system; 2-Focusing lens; Gain and frequency doubling section: 3-Nd:YAG gain crystal; 4-Ultra-thin fused silica phase homogenizer; 5-LBO nonlinear frequency doubling crystal; Output and Shaping Section: 6-Output Coupler; 7-Diverging Mirror; 8-Converging Mirror; Temperature control section: 9-Dual-zone independent temperature control system. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0024] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0025] First Embodiment Please see Figures 1 to 3 As shown, this is the first embodiment of the present invention. It should be noted that the accompanying drawings and the related quantities and shapes mentioned in this embodiment are only used to specifically illustrate the implementation of the present invention so as to facilitate understanding of the content of the present invention, and are not intended to limit the scope of protection of the present invention.

[0026] This invention provides a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser. Figure 1 This is a perspective view of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser according to an exemplary embodiment. Figure 2 This is a cross-sectional view of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser according to an exemplary embodiment. Figure 3 This is an optical path diagram of a three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser according to an exemplary embodiment. Figure 1-3 As shown, this three-wavelength co-cavity straight-cavity Nd:YAG-LBO frequency-doubled solid-state laser includes a pump source system 1, a focusing mirror 2, an Nd:YAG gain crystal 3, an ultrathin fused silica phase homogenizer 4, an LBO nonlinear frequency-doubled crystal 5, and an output coupling mirror 6 arranged sequentially along the optical axis. The overall structure is a linear flat-flat resonant cavity with no folded optical path and a cavity length of 85–110 mm. In this embodiment, a flat-flat cavity is chosen to maximize the shared gain region of the three spectral lines. Since a flat-flat cavity is a critically stable cavity, its fundamental mode volume is the largest among similar cavity types, resulting in high mode matching efficiency. Using a flat-concave cavity would introduce a mode selection effect, causing the fundamental mode volume within the cavity to shrink, which is detrimental to the simultaneous acquisition of sufficient gain cross-sections for the three fundamental frequencies. In addition, the longitudinal mode spacing corresponding to this cavity length range is adapted to allow the three fundamental frequency beams of 1112nm, 1116nm, and 1122nm to simultaneously meet the resonance condition in the cavity; the longitudinal mode spacing below 85mm is too large, which leads to the suppression of some spectral lines, and the diffraction loss in the cavity increases above 110mm, which is not conducive to the simultaneous oscillation of the three spectral lines.

[0027] Pump source system 1 employs an 808nm semiconductor laser end-face pump for operation in either continuous or pulsed mode, with a maximum output pump power of 5W to 10W. In this embodiment, when the pump power is below 5W, the oscillation thresholds of all three spectral lines cannot be reached simultaneously; above 10W, the thermal lensing effect of the Nd:YAG crystal is significant, disrupting the mode matching of the flat-flat cavity and causing output power fluctuations. The 5W to 10W range strikes a balance between threshold margin and thermal management.

[0028] The continuous mode is suitable for scenarios requiring stable and continuous output, such as spectral calibration and interferometry; the pulsed mode is suitable for scenarios requiring high peak power, such as biofluorescence excitation. The 808nm semiconductor laser supports direct electrical modulation, enabling mode switching without an external modulator.

[0029] Focusing lens 2 is a plano-convex aspherical lens with its plane facing the pump source system 1. The lens surface is coated with an 808nm anti-reflection film, focusing and coupling the pump light to the pump end face of the Nd:YAG gain crystal 3. The aspherical lens eliminates the inherent spherical aberration of spherical lenses, precisely coupling the pump spot to the Nd:YAG end face, achieving high overlap mode matching between the pump spot and the fundamental mode of the resonant cavity, and reducing pump energy leakage. Spherical lenses, due to spherical aberration, cause the pump spot to diffuse, reducing coupling efficiency and hindering the simultaneous attainment of the threshold values ​​for all three spectral lines.

[0030] The Nd:YAG gain crystal 3 has a doping concentration of 0.5 at.% to 1.5 at.% and a crystal size of 3 mm × 3 mm × 8 mm. When excited by 808 nm pump light, the crystal simultaneously generates three infrared fundamental spectrum lines at 1112 nm, 1116 nm, and 1122 nm. The incident end face of the Nd:YAG gain crystal 3 is coated with an 808 nm pump light anti-reflection film and three infrared fundamental frequency anti-reflection films, while the exit end face is coated with three fundamental frequency anti-reflection films. The fundamental frequency light transmittance of both end faces is greater than 98%, thus reducing intracavity round-trip loss. Specifically, the 808nm pump light antireflection coating allows the pump light to enter the crystal efficiently and be absorbed; three fundamental frequency antireflection coatings reduce Fresnel reflection loss of the fundamental frequency light at the crystal end face. Both the pump light and the fundamental frequency light enter the crystal from this end face, and the significant difference in wavelength allows for independent control of their respective transmittance through the double-layer film system.

[0031] The Nd:YAG gain crystal has a cross-section of 3mm×3mm to match the pump spot size and the cavity fundamental mode diameter; the length of 8mm enables the 808nm pump light to have an absorption rate of over 95% in single-pass propagation, fully extracting pump energy, while avoiding excessive length that would cause thermal stress concentration at the crystal end face and lead to wavefront distortion.

[0032] When the doping concentration is below 0.5 at.%, the gain is insufficient to support the simultaneous oscillation of the three spectral lines, and the weak lines are easily suppressed by the strong lines; when it is above 1.5 at.%, the concentration quenching effect leads to increased upconversion loss. The range of 0.5 at.% to 1.5 at.% keeps the gain coefficients of the three spectral lines at a comparable level, which is beneficial for synchronous oscillation of the three wavelengths.

[0033] In one possible design, continue to refer to Figures 1 to 3The ultrathin fused silica phase homogenizer 4 is disposed between the Nd:YAG gain crystal 3 and the LBO nonlinear frequency doubling crystal 5, and both sides are coated with antireflection films for the three infrared fundamental frequency beams of 1112nm, 1116nm, and 1122nm. The ultrathin fused silica phase homogenizer 4 utilizes the 5nm wavelength difference between the three fundamental frequency beams to introduce a small optical path difference, finely adjust the intracavity optical field distribution of the three fundamental frequency beams, balance the gain competition, and make the output power ratio of the three yellow beams of 556nm, 558nm, and 561nm continuously adjustable within the range of 1:0.8~1.2:1~1.5.

[0034] In one possible design, continue to refer to Figures 1 to 3 The LBO nonlinear frequency doubling crystal 5 is a crystal that meets the type I phase-matching cut requirement, with dimensions of 3mm × 3mm × 12mm. Both ends are coated with a full-band anti-reflection film covering 1112nm, 1116nm, and 1122nm infrared fundamental frequency light and 556nm, 558nm, and 561nm frequency-doubled yellow light. The fundamental frequency light transmittance is greater than 98%, and the frequency-doubled light transmittance is greater than 96%. Under the action of the intracavity reciprocating optical field, the LBO nonlinear frequency doubling crystal 5 simultaneously completes intracavity frequency doubling conversion of three wavelengths.

[0035] In this embodiment, the nonlinear coefficient of Type I phase matching is approximately twice that of Type II. Given the limited intracavity fundamental frequency power, Type I matching can achieve higher frequency doubling efficiency with lower fundamental frequency intensity, making it more suitable for intracavity frequency doubling schemes. While Type II matching has a smaller walk-off angle, its conversion efficiency is insufficient, which is not conducive to efficient frequency doubling of three wavelengths simultaneously.

[0036] The LBO crystal has a 3mm × 3mm cross-section to match the diameter of the fundamental frequency spot within the cavity, and a length of 12mm is an optimized value for detachment effect and conversion efficiency. Simultaneously, the effective nonlinear coefficient of the LBO crystal is proportional to its length. The 12mm length strikes a balance between detachment effect and nonlinear conversion efficiency; if the length is too short, the conversion efficiency will be insufficient to simultaneously support frequency doubling of three wavelengths; if it is too long, the detachment effect will cause the fundamental frequency and frequency-doubled light to gradually separate spatially, thus reducing the overall conversion efficiency.

[0037] In one possible design, continue to refer to Figure 1 The output coupling mirror 6 has a three-wavelength composite film coated on one side of its cavity: a transmittance greater than 95% for the 808nm antireflection coating; a reflectance R > 99.5% for the 1112nm, 1116nm, and 1122nm infrared fundamental frequencies using a high-reflection coating; and a transmittance greater than 92% for the 556nm, 558nm, and 561nm yellow light full-transmittance coating. The outer side of the output coupling mirror 6 is coated with a three-path yellow light antireflection coating. The focusing mirror 2 has the same coating specifications as the output coupling mirror 6, providing antireflection for the 808nm pump light, full reflection for the three infrared fundamental frequencies, and full transmittance for the three paths of yellow light.

[0038] In this embodiment, a transmittance greater than 95% ensures that the pump light is incident on the crystal with low loss, fully exciting the gain medium; R > 99.5% ensures that the round-trip loss of the fundamental frequency light in the cavity is less than 0.5%, guaranteeing that the oscillation thresholds of the three spectral lines remain at a low level; and a transmittance greater than 92% ensures efficient coupling and output of the frequency-doubled yellow light. The three thresholds are jointly determined by the balance between the gain coefficient, cavity loss, and output coupling rate. Simultaneously, an anti-reflection film is used to eliminate Fresnel reflection (approximately 4%) of the frequency-doubled yellow light at the air interface outside the output mirror, preventing reflected light from returning into the cavity and forming stray interference, while also improving the effective output power.

[0039] In one possible design, continue to refer to Figures 1 to 3 The dual-body zoned independent temperature control system 9 includes a first temperature-controlled heat sink, a second temperature-controlled heat sink, and an integrated micro-vibration-damping temperature control base. The first temperature-controlled heat sink is paired with an Nd:YAG gain crystal 3, with a temperature control accuracy of ±0.05℃, used to adjust the crystal's energy level gain distribution and match the gain coefficients of the three spectral lines at 1112nm, 1116nm, and 1122nm. The second temperature-controlled heat sink is paired with an LBO nonlinear frequency doubling crystal 5, independently adjusting the crystal's phase-matching temperature while simultaneously satisfying the Type I phase-matching conditions for three wavelengths. The operating temperature of this LBO nonlinear frequency doubling crystal is controlled at 45℃±1℃. The integrated micro-vibration-damping temperature control base is located on the resonant cavity mirror base to suppress wavelength shifts caused by environmental temperature drift and vibration.

[0040] In the above embodiment, the 808nm pump light is focused and coupled to the Nd:YAG gain crystal 3 by the focusing mirror 2. The generated 1112nm, 1116nm, and 1122nm infrared fundamental frequency light oscillates continuously in the resonant cavity composed of the high-reflectivity film of the focusing mirror 2 and the output coupling mirror 6. After being frequency-doubled in the cavity by the LBO nonlinear frequency doubling crystal 5, it is converted into three yellow light beams of 556nm, 558nm, and 561nm, which are transmitted and output through the all-transmitting film of the output coupling mirror 6. The dual-body zoned independent temperature control system 9 independently controls the temperature of the gain crystal and the frequency doubling crystal, so that the gain coefficients of the three spectral lines are matched and the phases of the three wavelengths are synchronously matched. With the help of the ultrathin fused silica phase homogenizer 4, the gain competition is balanced, and the three wavelengths are synchronously coaxially output. The output spectrum is free of random clutter peaks, the wavelength drift is less than 0.03nm / 8h, and the power fluctuation is less than 3%.

[0041] The 3% power fluctuation is within an acceptable range for laser displays and biomedical imaging, reflecting that the dual-body temperature control system manages gain and phase mismatch fluctuations at this level, ensuring the amplitude consistency of the three yellow light outputs. 0.03nm corresponds to approximately 0.1cm in the yellow light band. ﹣1 The wavenumber drift is less than the resolution limit of a typical spectrometer, and its impact on applications such as biological fluorescence excitation and spectral calibration is negligible. This value corresponds to the upper limit of thermally induced wavelength drift that a dual-body temperature control system can suppress with a temperature control accuracy of ±0.05℃.

[0042] In summary, the three-wavelength co-cavity direct-cavity Nd:YAG-LBO frequency-doubled solid-state laser provided in this embodiment differs from the industry's approach of suppressing redundant spectral lines. By using three-wavelength composite films deposited on the focusing mirror and output coupling mirror, three infrared fundamental frequency beams are synchronously oscillating within the same resonant cavity. This is combined with an ultrathin fused silica phase homogenizer that uses wavelength differences to introduce optical path differences to balance gain competition. Furthermore, a dual-body zoned independent temperature control system independently regulates the gain distribution and phase matching conditions. The single resonant cavity synchronously outputs three coaxial and co-directional yellow beams of 556nm, 558nm, and 561nm, replacing the combination scheme of three independent single-wavelength lasers. This results in a compact structure and stable output.

[0043] Second Embodiment Continue to refer to Figures 1-3 This is the second embodiment of the present invention. It should be noted that this embodiment is similar to the first embodiment described above, so the similarities between the two embodiments will not be repeated. Furthermore, for ease of explanation and understanding, this embodiment will be described in conjunction with the accompanying drawings of the first embodiment described above. The quantities and shapes mentioned in the accompanying drawings are only used to specifically illustrate the implementation of the present invention so as to facilitate understanding of the content of the present invention, and are not intended to limit the scope of protection of the present invention.

[0044] Continue to refer to Figures 1-3 The second embodiment of the present invention further includes a post-beam shaping assembly, which comprises a diverging mirror 7 and a converging mirror 8 arranged sequentially along the output optical path. The diverging mirror 7 is coated with a three-way yellow anti-reflection film on both sides to expand the output beam aperture and compress the divergence angle. The converging mirror 8 is coated with a three-way yellow anti-reflection film on both sides, forming an inverted beam expanding and collimating system with the diverging mirror 7. The focal length ratio of the diverging mirror 7 to the converging mirror 8 is within 1.2 to 1.9.

[0045] In the above embodiment, the lower limit of the focal length ratio between the diverging mirror 7 and the converging mirror 8 is 1.2, which ensures sufficient divergence angle compression, enabling the divergence angle of the three yellow light output beams to reach a practical level and preventing excessive diffusion of the beams after long-distance transmission. The upper limit is 1.9, which limits the beam expansion ratio, preventing excessively large output spot diameters that could lead to difficulties in subsequent optical path adaptation, while maintaining system compactness. In summary, this focal length ratio range of 1.2 to 1.9 optimizes the spot roundness, shaping the three coaxial yellow light beams into parallel light outputs, ensuring that the three beams (556nm / 558nm / 561nm) maintain coaxiality in the far field.

[0046] The remaining structure is the same as in the first embodiment.

[0047] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included in the scope of the patent application of the present invention.

Claims

1. A three-wavelength common-cavity direct-cavity Nd:YAG-LBO frequency-doubled solid-state laser, comprising a pump source system, a focusing mirror, an Nd:YAG gain crystal, an LBO nonlinear frequency-doubled crystal, and an output coupling mirror arranged sequentially along the optical axis, wherein the pump source system is an 808nm semiconductor laser end-face pump, characterized in that, It also includes: An ultrathin fused silica phase homogenizer is disposed between the Nd:YAG gain crystal and the LBO nonlinear frequency doubling crystal; The dual-body zoned independent temperature control system includes at least a first temperature control heat sink, a second temperature control heat sink, and an integrated micro-vibration damping temperature control base. The first temperature control heat sink is paired with the Nd:YAG gain crystal, and the second temperature control heat sink is paired with the LBO nonlinear frequency doubling crystal. The focusing lens and the output coupling lens are each coated with a three-wavelength composite film. The three-wavelength composite film is anti-reflective for 808nm, totally reflective for 1112nm, 1116nm, and 1122nm infrared fundamental frequencies, and totally transmittable for 556nm, 558nm, and 561nm yellow light. The 808nm pump light from the pump source system is coupled to the Nd:YAG gain crystal via the focusing lens. The resulting 1112nm, 1116nm, and 1122nm infrared fundamental frequency light is frequency-doubled in the resonant cavity by the LBO nonlinear frequency doubling crystal and converted into 556nm, 558nm, and 561nm yellow light, which is then output by the output coupling lens.

2. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The ultrathin fused silica phase homogenizer uses the wavelength difference of the three fundamental frequency lights to introduce an optical path difference to fine-tune the optical field distribution in the cavity, so that the output power ratio of the three yellow lights of 556nm, 558nm and 561nm can be continuously adjusted in the range of 1:0.8~1.2:1~1.

5.

3. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The temperature control accuracy of the first temperature-controlled heat sink is ±0.05℃, which is used to regulate the energy level gain distribution by adjusting the crystal temperature so that the gain coefficients of 1112nm, 1116nm, and 1122nm are close to matching.

4. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The doping concentration of the Nd:YAG gain crystal is 0.5 at.% to 1.5 at.%.

5. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The LBO nonlinear frequency doubling crystal is a crystal that satisfies type I phase matching, and its crystal size is 3mm×3mm×12mm.

6. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, In the three-wavelength composite film: The transmittance of the 808nm antireflection coating is greater than 95%; The reflectivity R of the high-reflectivity film for the 1112nm, 1116nm, and 1122nm infrared fundamental frequencies is greater than 99.5%; The transmittance of the fully transparent film for 556nm, 558nm, and 561nm yellow light is greater than 92%.

7. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The resonant cavity is a linear flat-flat cavity structure with a cavity length of 85–110 mm.

8. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The Nd:YAG gain crystal has a crystal size of 3mm × 3mm × 8mm.

9. The three-wavelength common-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, The maximum output pump power of the pump source system is 5W to 10W.

10. The three-wavelength co-cavity linear Nd:YAG-LBO frequency-doubled solid-state laser as described in claim 1, characterized in that, It also includes a rear beam shaping assembly. The rear beam shaping assembly includes a diverging lens and a converging lens arranged sequentially along the output optical path. The focal length ratio of the diverging lens to the converging lens is within 1.2 to 1.9, and both sides of the diverging lens and the converging lens are coated with a three-way yellow light anti-reflection film.

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