Solid laser of spectrum beam combination semiconductor laser pump

Abstract

The invention discloses a solid-state laser of a spectrum beam combination semiconductor laser pump. The solid-state laser comprises a spectrum beam combination pumping source system, a pumping coupling system and a solid-state laser resonant cavity, pump light emitted by the spectrum beam combination pump source system is collimated and focused through the pump coupling system and then enters a gain medium of the solid laser resonant cavity, generated oscillation light of a first wavelength oscillates in the solid laser resonant cavity in a reciprocating mode, and laser output of a second wavelength is achieved. High-power pumping can be carried out on the gain medium under the condition that the quality of pumping laser beams is not reduced, the problem that the quality of the beams is poor in traditional semiconductor laser direct pumping is solved, and a research basis is provided for follow-up power improvement.

Description

Technical Field

[0001] This invention relates to the field of solid-state laser technology, and more specifically to a solid-state laser pumped by a spectral beam semiconductor laser. Background Art

[0002] Semiconductor lasers possess advantages such as small size, long lifespan, high efficiency, and compact structure. Thanks to these superior characteristics, they have been widely used in numerous fields including medical, materials processing, solid-state laser pumping, industrial, and aerospace applications.

[0003] Visible lasers, due to their unique wavelength range, are widely used in various fields such as laser displays, medicine, biological detection, optical communication, and atmospheric measurement. Praseodymium-doped yttrium lithium fluoride (Pr:YLF) crystals exhibit excellent laser performance, directly acquiring multiple transition lines in the visible light band, providing an important means of obtaining visible laser light. Currently, a significant factor limiting the development of Pr:YLF lasers is the relatively low pump power of blue semiconductor pump sources. Higher pump power implies poorer beam quality, easily leading to reduced efficiency.

[0004] Spectral beam combining technology involves adding a diffraction grating, such as a transmission grating or a reflection grating, to an optical system that matches the wavelength of the laser emitting units participating in beam combining. By utilizing the dispersion effect of the grating, lasers incident at different angles to the grating have the same exit angle, thus combining the beams of each emitting unit into a single laser output. The final output laser beam quality is essentially the same as that of a single emitting unit, while the total output power is the sum of the output power of each emitting unit. Summary of the Invention

[0005] To address the shortcomings of existing technologies and to continuously explore the broad applications of blue light-pumped Pr:YLF lasers, this invention provides a solid-state laser pumped by a spectral-beamed semiconductor laser, which can pump the gain medium at high power without reducing the quality of the pump laser beam.

[0006] This invention discloses a solid-state laser pumped by a spectral beam semiconductor laser, comprising: a spectral beam pump source system, a pump coupling system, and a solid-state laser resonator.

[0007] The pump light emitted from the spectral beam pump source system is collimated and focused by the pump coupling system and then enters the gain medium of the solid-state laser resonator. The resulting first-wavelength oscillating light oscillates back and forth in the solid-state laser resonator, achieving the output of the second-wavelength laser.

[0008] As a further improvement of the present invention, the spectral beam-combining pump source system includes a semiconductor laser array, a transmission conversion lens, a beam-combining dispersive element, and an output coupling mirror arranged sequentially in the optical path. The semiconductor laser array includes multiple continuously output semiconductor lasers. The laser beams from the multiple semiconductor lasers are incident on the beam-combining dispersive element through the transmission conversion lens. The beam-combining dispersive element outputs incident light from different angles at the same exit angle, thus completing laser beam combining. After beam combining, the laser beam is reflected by the output coupling mirror. Part of the light passes through the output coupling mirror and is directly output, while the other part is reflected back for feedback. The beam oscillates in the resonant cavity formed by the output coupling mirror and the rear end face of the laser semiconductor laser and achieves wavelength locking, thereby completing spectral beam combining and obtaining pump light output outward.

[0009] As a further improvement of the present invention, the semiconductor laser array is a plurality of semiconductor lasers that continuously output blue light, near-infrared light or infrared light, preferably a semiconductor laser array of nine semiconductor lasers that continuously output blue light (output wavelength around 445nm).

[0010] As a further improvement of the present invention, the transmission conversion lens is a plano-convex cylindrical mirror, used to incident lasers from different semiconductor lasers onto the beam-forming dispersive element; the output coupling mirror is a planar reflector, and after reflection by the output coupling mirror, part of the light passes through the output coupling mirror and is directly output, while the other part of the light is reflected back for feedback, oscillating in the resonant cavity formed by the output coupling mirror and the rear end face of the laser semiconductor laser and achieving wavelength locking.

[0011] As a further improvement of the present invention, the dispersive element for beam assembly includes one of a diffraction grating, a prism, a transmission grating, and a reflection grating.

[0012] As a further improvement of the present invention, the beam-forming dispersive element is a diffraction grating, which is a transmission grating. Through the dispersive effect of the transmission grating, beams incident at different angles are dispersed to the output coupling mirror in the same direction.

[0013] The period of the diffraction grating is 2500 lines / mm, and the beams participating in the beam combining satisfy the grating equation:

[0014] mλ=d(sinθ i +sinθ d )

[0015] In the formula, m is the diffraction order, λ is the center wavelength of the beam, d is the grating constant, and θ is the reticle constant. i Let θ be the angle of incidence. d It is the diffraction angle.

[0016] As a further improvement of the present invention, the pump coupling system includes a plano-convex cylindrical lens, a plano-concave cylindrical lens and a focusing lens arranged sequentially along the transmission direction of the pump light, which is used to compress and focus the pump laser in the fast axis direction so that the size of the light spot near the focal point is basically the same as that in the slow axis direction, and then guide it to the front end of the gain medium through the focusing lens.

[0017] As a further improvement of the present invention, the solid-state laser resonant cavity includes a gain medium, an output mirror, and a dichroic mirror arranged sequentially along the beam direction.

[0018] As a further improvement of the present invention, the gain medium is a 3×3×22mm Pr:YLF crystal with a doping concentration of 0.5at%, or it can be a solid laser gain medium such as Nd:YAG or Yb:YAG. The front end of the gain medium is coated with a first wavelength anti-reflection (blue light anti-reflection) and a second wavelength total reflection film (red light total reflection), and the rear end of the gain medium is coated with a first wavelength and a second wavelength anti-reflection film.

[0019] As a further improvement of the present invention, the output mirror is a plano-concave mirror coated with a second wavelength (red light) reflective film with a transmittance T = 5%, and the dichroic mirror is a short-wavelength pass mirror used to transmit the pump beam of the first wavelength (blue light) while reflecting the output laser beam of the second wavelength (red light).

[0020] Furthermore, the coating of the plano-concave output mirror includes, but is not limited to, a 640nm output laser reflective film, and can also be an output laser reflective film of other wavelengths such as 522nm and 720nm. Similarly, the output laser should also include lasers of other wavelengths.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] On the one hand, this invention can pump the gain medium with high power while ensuring the quality of the pump beam. On the other hand, the center wavelength of the pump light can be adjusted to better match the absorption peak of the gain medium. Moreover, the overall laser structure is relatively simple and compact. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the solid-state laser disclosed in this invention;

[0024] Figure 2 The images show the absorption spectrum of the gain medium Pr:YLF crystal and the spectrum of the spectral beam pump source system disclosed in this invention.

[0025] In the picture:

[0026] 1. Semiconductor laser array; 2. Transmission conversion lens; 3. Diffraction grating; 4. Output coupling mirror; 5. Pump light; 6. Pump coupling system; 7. Gain medium; 8. Plano-concave output mirror; 9. Dichroic mirror; 10. Output laser. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings:

[0029] This invention provides a solid-state laser pumped by a spectral-beamed semiconductor laser, comprising: a spectral-beamed pump source system, a pump coupling system, and a solid-state laser resonator. The pump light emitted from the spectral-beamed pump source system is collimated and focused by the pump coupling system and then enters the gain medium of the solid-state laser resonator. The resulting oscillating light oscillates reciprocally within the solid-state laser resonator, achieving laser output. The laser output utilizes a semiconductor laser closed-loop structure for spectral beam combining, coupled with an output coupling mirror coated with a reflective film to achieve wavelength locking, thereby ensuring that the wavelength of the pump light matches the absorption peak of the Pr:YLF crystal. This structure enables the output of a 640nm red solid-state laser.

[0030] Specifically:

[0031] like Figure 1 As shown, the spectral beam pumping source system of the present invention includes a semiconductor laser array 1, a transmission conversion lens 2, a diffraction grating 3, and an output coupling mirror 4 arranged sequentially in the optical path. The semiconductor laser array 1 includes nine continuously output semiconductor lasers, each of which (emitting unit) can emit approximately 3.5W of laser output. The beam emitted from each individual semiconductor laser passes through its respective fast-axis collimating lens and slow-axis collimating lens. The fast-axis collimating lens is a high-order aspherical cylindrical lens with a focal length of 300µm; the slow-axis collimating lens is a plano-convex cylindrical lens with a focal length of 12mm. The fast-axis and slow-axis collimating lenses collimate the laser beam emitted from the semiconductor lasers in two directions. The transmission conversion lens 2 includes a plano-convex cylindrical lens with a focal length of 200mm, which can change the optical path, thereby directing the laser beams from multiple semiconductor lasers to the diffraction grating 3. Diffraction grating 3 has a dispersive effect. The grating size is 31×15mm, with 2500 lines / mm. The beams participating in the beam combining satisfy the grating equation: mλ=d(sinθ) i+sinθ d In the formula, m is the diffraction order, λ is the center wavelength of the beam, d is the grating constant, and θ is the reticle constant. i Let θ be the angle of incidence. d The diffraction angle is used to ensure that lasers incident at different angles to the grating have the same exit angle, thus combining the beams of individual semiconductor lasers into a single output laser beam. The final output laser beam quality is essentially the same as that of a single semiconductor laser, and the total output power is the sum of the output powers of each individual semiconductor laser. After beam combining through the diffraction grating 3, the laser beam is reflected by the output coupling mirror 4. Part of the light passes directly through the output coupling mirror 4, while the other part is reflected back for feedback. The beam oscillates in the resonant cavity formed by the output coupling mirror 4 and the rear facet of the laser semiconductor laser, achieving wavelength locking and thus completing spectral beam combining to obtain the pump light 5 output outwards. The pump light 5 has a power of 25W and a beam quality M. 2 x =1.4, M 2 y =13.

[0032] like Figure 1 As shown, the solid-state laser resonator of the present invention includes a gain medium 7, an output mirror 8, and a dichroic mirror 9 arranged sequentially along the beam direction. A pump coupling system 6 is used to focus the pump light 5 into the gain medium 7 of the solid-state laser resonator. The pump coupling system 6 consists of three parts, namely a plano-convex cylindrical lens, a plano-concave cylindrical lens, and a focusing mirror, arranged along the propagation direction of the pump light 5. It compresses and focuses the pump laser along the fast axis, making the spot size near the focal point essentially the same as that along the slow axis, and then guides it to the front end of the gain medium 7 through the focusing mirror. The gain medium 7 is a 3×3×22mm Pr:YLF crystal with a doping concentration of 0.5at%. The end face of the gain medium 7 is coated with an anti-reflection coating of 444nm and a total reflection coating of 640nm. The rear end face of the gain medium 7 is coated with anti-reflection coatings of 444nm and 640nm. The output mirror 8 is a plano-concave mirror coated with a 640nm reflective coating of T=5%. The reflective coating of the output mirror 8 and the front end face of the gain medium 7 form a closed loop for laser oscillation. The output light from the output mirror 8 is incident on a dichroic mirror 9, which is a short-wavelength pass mirror used to transmit the 445nm pump beam and reflect the 640nm output laser beam, reflecting the output laser 10 to other optical components such as a power meter for easy measurement. The absorption spectrum of the gain medium Pr:YLF crystal and the spectrum of the spectral beam pump source system are shown in the figure. Figure 2 As shown.

[0033] The advantages of this invention are:

[0034] 1. This invention uses a spectral-beamed semiconductor laser for pumping, combining the beams of individual semiconductor lasers into a single output laser beam. The quality of the combined output laser beam is basically the same as that of the individual semiconductor laser beams, and the total output power is the sum of the output power of each semiconductor laser. This is beneficial for increasing pump power while ensuring beam quality.

[0035] 2. The spectral beam-combining pump source system used in this invention is based on a closed-loop structure spectral beam combiner using a conventional transmission diffraction grating. In this structure, the center wavelength locking of each semiconductor laser is automatically achieved by external cavity feedback. The center wavelength can be adjusted by adjusting the output coupling mirror, thereby making the pump light more matched with the crystal absorption peak of the gain medium.

[0036] 3. Compared with traditional polarization beam combiners and dual-end pumps, which do not have optical isolators, polarization beam splitters, or other optical components, the overall structure of this invention is simpler and facilitates the adjustment and collimation of the optical path.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solid-state laser pumped by a spectral-beaming semiconductor laser, characterized in that, include: Spectral beam pump source system, pump coupling system, and solid-state laser resonator; The pump light emitted from the spectral beam pump source system is collimated and focused by the pump coupling system and then enters the gain medium of the solid-state laser resonator. The resulting first-wavelength oscillating light oscillates back and forth in the solid-state laser resonator, achieving the output of the second-wavelength laser.

2. The solid-state laser as described in claim 1, characterized in that, The spectral beam-combining pump source system includes a semiconductor laser array, a transmission conversion lens, a beam-combining dispersive element, and an output coupling mirror sequentially arranged in the optical path. The semiconductor laser array includes multiple continuously output semiconductor lasers. The laser beams from the multiple semiconductor lasers are incident on the beam-combining dispersive element through the transmission conversion lens. The beam-combining dispersive element outputs incident light from different angles at the same exit angle, thus completing laser beam combining. After beam combining, the laser beam is reflected by the output coupling mirror. Part of the light passes through the output coupling mirror and is directly output, while the other part is reflected back for feedback. The output coupling mirror and the rear end face of the laser semiconductor laser oscillate in the resonant cavity to achieve wavelength locking, thereby completing spectral beam combining and obtaining the pump light output outward.

3. The solid-state laser as described in claim 2, characterized in that, The semiconductor laser array consists of multiple semiconductor lasers that continuously output blue light, near-infrared light, or infrared light.

4. The solid-state laser as described in claim 2, characterized in that, The transmission conversion lens is a plano-convex cylindrical mirror used to direct laser light from different semiconductor lasers onto the beam-forming dispersive element; the output coupling mirror is a plane mirror.

5. The solid-state laser as described in claim 2 or 4, characterized in that, The dispersive element for beamforming includes one of a diffraction grating, a prism, a transmission grating, and a reflection grating.

6. The solid-state laser as described in claim 5, characterized in that, The beam-forming dispersive element is a diffraction grating, which is a transmission grating. Through the dispersive effect of the transmission grating, beams incident at different angles are dispersed to the output coupling mirror in the same direction. The period of the diffraction grating is 2500 lines / mm, and the beams participating in the beam combining satisfy the grating equation: mλ=d(sinθ i +sinθ d ) In the formula, m is the diffraction order, λ is the center wavelength of the beam, d is the grating constant, and θ is the reticle constant. i Let θ be the angle of incidence. d It is the diffraction angle.

7. The solid-state laser as claimed in claim 1, characterized in that, The pump coupling system includes a plano-convex cylindrical lens, a plano-concave cylindrical lens, and a focusing lens arranged sequentially along the transmission direction of the pump light. It is used to compress and focus the pump laser in the fast axis direction so that the size of the spot near the focal point is consistent with that in the slow axis direction, and then guide it to the front end of the gain medium through the focusing lens.

8. The solid-state laser as claimed in claim 1, characterized in that, The solid-state laser resonant cavity includes a gain medium, an output mirror, and a dichroic mirror arranged sequentially along the beam direction.

9. The solid-state laser as claimed in claim 8, characterized in that, The gain medium is a Pr:YLF crystal. The front end of the gain medium is coated with a first wavelength antireflection film and a second wavelength total reflection film, and the rear end of the gain medium is coated with a first wavelength and a second wavelength antireflection film.

10. The solid-state laser as claimed in claim 8, characterized in that, The output mirror is a plano-concave mirror coated with a second-wavelength reflective film with a transmittance T = 5%. The dichroic mirror is a short-wavelength pass mirror used to transmit the pump beam of the first wavelength while reflecting the output laser beam of the second wavelength.

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