阅读说明：本技术 一种线偏振Ho激光器 (Linear polarization Ho laser ) 是由 黄海洲 林文雄 邓晶 李锦辉 葛燕 黄见洪 于 2020-05-20 设计创作，主要内容包括：本申请公开了一种激光器,包括：谐振腔、板条增益介质和泵浦源,所述泵浦源产生泵浦光耦合所述板条增益介质,所述板条增益介质设置于所述谐振腔内；所述板条增益介质与激光传输方向垂直的任一截面的长宽比大于2；所述板条增益介质包括复合的掺铥部分和掺钬部分；所述泵浦光泵浦所述掺铥部分产生禁锢在所述谐振腔内的铥激光,所述铥激光同带泵浦所述掺钬部分,输出2.1μm波段的所述钬激光,该激光器结构简单,能直接产生高功率的线偏振2.1μm波段Ho激光。(The application discloses laser instrument includes: the slab gain medium comprises a resonant cavity, a slab gain medium and a pumping source, wherein the pumping source generates pumping light to be coupled with the slab gain medium, and the slab gain medium is arranged in the resonant cavity; the aspect ratio of any section of the slab gain medium perpendicular to the laser transmission direction is larger than 2; the slab gain medium comprises a thulium-doped part and a holmium-doped part which are compounded; the pump optical pumping mixes the thulium part and produces and is confined thulium laser in the resonant cavity, thulium laser is with the band pump mix the holmium part, output 2.1 mu m wave band the holmium laser, this laser structure is simple, can directly produce the linear polarization 2.1 mu m wave band Ho laser of high power.)

1. A linearly polarized Ho laser, comprising: the slab gain medium coupling structure comprises a resonant cavity, a slab gain medium and a pumping source, wherein the pumping source generates pumping light and is coupled with the slab gain medium after being shaped, and the slab gain medium is arranged in the resonant cavity;

the aspect ratio of any section of the slab gain medium perpendicular to the laser transmission direction is larger than 2;

the slab gain medium comprises a thulium-doped part and a holmium-doped part which are compounded;

the laser outputs linearly polarized holmium laser with a wave band of 2.1 mu m.

2. The linearly polarized Ho laser according to claim 1, wherein the slab gain medium comprises a first thulium-doped part and a first holmium-doped part, which are sequentially compositely arranged along the laser propagation direction.

3. The linearly polarized Ho laser according to claim 1, wherein the slab gain medium comprises a first thulium doped portion, a first holmium doped portion, and a second thulium doped portion;

the first thulium-doped part, the first holmium-doped part and the second thulium-doped part are sequentially and compositely arranged along the laser transmission direction.

4. The linearly polarized Ho laser according to claim 1, wherein the slab gain medium further comprises: an undoped portion;

the undoped part is compounded on the end face, far away from the holmium-doped part, of the thulium-doped part;

preferably, the slab gain medium comprises a first undoped portion, a first thulium-doped portion and a first holmium-doped portion;

the first undoped part, the first thulium-doped part and the first holmium-doped part are sequentially and compositely arranged along the laser transmission direction;

preferably, the slab gain medium comprises a first undoped part, a first thulium-doped part, a first holmium-doped part, a second thulium-doped part and a second undoped part;

the first undoped part, the first thulium-doped part, the first holmium-doped part, the second thulium-doped part and the second undoped part are sequentially and compositely arranged along the laser transmission direction.

5. The linearly polarized Ho laser according to claim 1, wherein the thulium doped portion is a thulium doped laser gain medium; the holmium-doped part is a holmium-doped laser gain medium; the laser gain medium is the same kind of laser gain material.

6. The linearly polarized Ho laser according to claim 5, wherein the working substance of the laser gain medium is a uniaxial crystal having a natural birefringence property, or a biaxial crystal having a natural birefringence property.

7. The linearly polarized Ho laser according to claim 1, wherein the two opposite surfaces of the slab gain medium parallel to the X-axis direction are respectively coated with an evanescent wave protection layer.

8. The linearly polarized Ho laser according to claim 1, wherein the pump light is 800nm band pump laser light.

9. The linearly polarized Ho laser according to claim 1, wherein the laser further comprises: a thermal management section;

the thermal management section includes: the heat sink comprises a heat sink body and a plurality of water nozzles;

the slab gain medium is clamped in the heat sink body along the transverse direction of the heat sink body;

the water nozzle is arranged on the heat sink main body and communicated with the micro-channel in the heat sink main body, and cooling liquid flows in the micro-channel.

10. The linearly polarized Ho laser according to claim 1, wherein an aspect ratio of a cross section of the pump-light-shaped spot perpendicular to the X-axis is greater than or equal to an aspect ratio of a light-passing surface of the slab gain medium;

wherein the direction of the X axis is the laser transmission direction;

and the light passing surface of the slab gain medium is any section of the slab gain medium vertical to the transmission direction of the laser.

Technical Field

The application relates to a linear polarization Ho laser, which belongs to the field of solid laser.

Background

Common implementations of all-solid-state holmium (Ho) lasers include: gallium aluminum arsenide laser semiconductor (LD) (wavelength range 750 nm-810 nm) pumping thulium (Tm) ion sensitized Tm and Ho codoped laser; 1.9 μm laser pump single-doped holmium laser; a thulium laser cavity resonance pumping holmium laser, and a Tm/Ho bonding laser.

Because the Ho ions do not have an absorption band near the 800nm wave band, the highly mature gallium aluminum arsenide LD cannot be utilized, and conventionally, the Ho ions and the Tm ions need to be doped in the same gain medium together to realize Ho laser output. However, such lasers suffer from severe cooperative upconversion losses, with only a few milliwatts of laser output at room temperature, and even no light output.

The 1.9 μm laser-pumped Ho laser is currently the most popular high-power Ho laser implementation. The 1.9 μm pump sources can be Tm doped fiber lasers, Tm doped all-solid-state lasers, and 1.9 μm semiconductor lasers. The adoption of a 1.9 mu m thulium-doped all-solid-state or optical fiber laser to realize Ho laser output is a cascade pump structure: namely, the Tm-doped gain medium in the GaAs-Al LD pumped Tm laser resonant cavity generates 1.9 μm laser, and then the Ho-doped gain medium is doped in the resonant cavity of the pumped Ho laser. The 1.9 micron pump source is also a laser, high-power 800nm semiconductor is needed for pumping, and then high-power Ho laser output can be realized through a plurality of 1.9 micron lasers, so that the whole Ho laser system is complex in structure, large in size and high in manufacturing cost, and the light-light conversion efficiency from LD to the final Ho laser output is low.

Although the structure of the 1.9 mu mLD pump holmium laser is more compact, 30-40% of light-light conversion efficiency can be realized at present. However, the price of a single bar used in a 1.9 μmLD laser is an order of magnitude higher than the price of a conventional aluminum gallium arsenide LD; the emission spectrum width reaches 15nm, which is not beneficial to matching the absorption peak (3-5 nm wide) of the Ho-doped gain medium.

The Tm/Ho bonding laser is established on the basis of an intracavity pumping Ho laser, and Tm-doped and Ho-doped gain media are bonded into the same gain medium, so that Ho laser output can be efficiently realized under the pumping of a conventional gallium aluminum arsenide (GaAs) Laser Diode (LD), and the Tm/Ho bonding laser is more compact and more convenient than the intracavity pumping Ho laser. However, because the existing Tm/Ho bonding gain medium is a rod-shaped structure (the light-passing surface is square or circular), the thermal effect inside the gain medium cannot be effectively controlled, so that the laser output power is lower than 10W, and further improvement cannot be achieved. In addition, the existing Tm/Ho bonding laser adopts isotropic YAG crystals, so that the linear polarization laser output cannot be directly realized, and the practicability in various application fields such as nonlinear frequency conversion, material processing, laser radar and the like is restricted. Therefore, it is urgently needed to develop a novel laser capable of realizing high-power linearly polarized Ho output under conventional LD pumping.

Disclosure of Invention

The application provides a linear polarization Ho laser capable of realizing high-power laser output, which takes bonded thulium-doped gain medium and holmium-doped gain medium as slab gain medium, and laser working substance is uniaxial or biaxial crystal with natural birefringence, and can realize linear polarization and high-power output of Ho laser with 2.1 μm wave band on the compact structure of conventional semiconductor laser LD pumping.

A linearly polarized Ho laser, comprising: the slab gain medium coupling structure comprises a resonant cavity, a slab gain medium and a pumping source, wherein the pumping source generates pumping light and is coupled with the slab gain medium after being shaped, and the slab gain medium is arranged in the resonant cavity;

the aspect ratio of any section of the slab gain medium perpendicular to the laser transmission direction is larger than 2;

the slab gain medium comprises a thulium-doped part and a holmium-doped part which are compounded;

the laser outputs linearly polarized holmium laser with a wave band of 2.1 mu m.

Optionally, the slab gain medium includes a first thulium-doped portion and a first holmium-doped portion, and the first thulium-doped portion and the first holmium-doped portion are sequentially and compositely arranged along the laser transmission direction.

Optionally, the slab gain medium includes a first thulium doped portion, a first holmium doped portion, and a second thulium doped portion;

the first thulium-doped part, the first holmium-doped part and the second thulium-doped part are sequentially and compositely arranged along the laser transmission direction.

Optionally, the slab gain medium further comprises: an undoped portion;

the undoped part is compounded on the end face, far away from the holmium-doped part, of the thulium-doped part.

Optionally, the slab gain medium comprises a first undoped portion, a first thulium-doped portion and a first holmium-doped portion; the first undoped part, the first thulium-doped part and the first holmium-doped part are sequentially and compositely arranged along the laser transmission direction.

Optionally, the slab gain medium includes a first undoped portion, a first thulium-doped portion, a first holmium-doped portion, a second thulium-doped portion, and a second undoped portion;

the first undoped part, the first thulium-doped part, the first holmium-doped part, the second thulium-doped part and the second undoped part are sequentially and compositely arranged along the laser transmission direction.

Optionally, the thulium-doped part is a thulium-doped laser gain medium; the holmium-doped part is a holmium-doped laser gain medium; the laser gain medium is the same kind of laser gain material.

Alternatively, the working substance of the laser gain medium is a uniaxial crystal having a natural birefringence characteristic, or a biaxial crystal having a natural birefringence characteristic.

Optionally, two opposite surfaces of the slab gain medium parallel to the X axis are respectively plated with an evanescent wave protection layer.

Optionally, the pump light is 800nm band pump laser.

Optionally, the laser further comprises: a thermal management section;

the thermal management section includes: the heat sink comprises a heat sink body and a plurality of water nozzles;

the slab gain medium is clamped in the heat sink body along the transverse direction of the heat sink body;

the water nozzle is arranged on the heat sink main body and communicated with the micro-channel in the heat sink main body, and cooling liquid flows in the micro-channel.

Optionally, the aspect ratio of a cross section of the spot, which is perpendicular to the X axis, after the pump light is shaped is greater than or equal to the aspect ratio of the light passing surface of the slab gain medium;

wherein the direction of the X axis is the laser transmission direction;

and the light passing surface of the slab gain medium is any section of the slab gain medium vertical to the transmission direction of the laser.

Optionally, the cavity mirror of the resonant cavity is perpendicular to the laser transmission direction to form a linear cavity.

Optionally, a cavity mirror of the resonant cavity is parallel to the laser transmission direction to form a folded cavity.

In the present application, "aspect ratio" refers to the ratio of the long side to the short side of the longitudinal section of the slab gain medium.

The beneficial effects that this application can produce include:

1) the application provides a laser, includes: thulium/holmium composite lath gain medium, pumping source and chamber mirror, lath gain medium includes at least: thulium-doped and holmium-doped parts, and the length-width ratio of the slab gain medium is more than or equal to 2. Pump light is incident into the slab gain medium from the end face of the slab gain medium, thulium-doped parts in the slab gain medium fully absorb the pump light to form particle number inversion of thulium ions, and thulium laser which is confined in the resonant cavity and can be mixed with holmium-doped parts of the band pump is generated under the effect of the resonant cavity mirror. Under the same-band pump of thulium laser, the linear polarization output of holmium laser with the wave band of 2.1 mu m is realized by utilizing the natural birefringence characteristic of a gain medium.

2) Compared with the existing Tm/Ho bonding gain medium with a square or round rod-shaped light-passing surface, the Tm-doped gain medium and the Ho-doped gain medium are bonded into a lath structure, the length-width ratio of the lath gain medium is more than or equal to 2, the internal thermal effect of the gain medium can be effectively controlled, the serious deterioration of the laser beam quality along with the increase of pumping power is avoided, and the linear polarization Ho laser output at room temperature with high beam quality (the wavelength is 2129.0-2130.0 nm) and high power (17-18W) can be realized under the pumping of a conventional high-power semiconductor.

3) Compared with a conventional mode of end face pumping by adopting an optical fiber coupling semiconductor, the Tm/Ho bonding laser focuses a pumping incident light spot into a circular light spot, the implementation mode of the laser provided by the application shapes the pumping light spot into a rectangular or linear light spot with the length-width ratio larger than or equal to the length-width ratio of the end face of the composite slab gain medium, the maximum pumping power bearable by the gain medium is improved, and the output of high-power Ho laser is further realized.

4) Compared with the conventional high-power holmium laser implementation mode, the holmium laser implementation mode is more convenient and more economical, and high-power laser output can be realized without liquid nitrogen cooling; the use cost of the 1.9 mu m thulium laser pumping source is reduced, and the structure is simplified; the problems of high cost, unmatched pumping wavelength, pumping energy leakage waste and the like of the existing 1.9 mu mLD are solved.

Drawings

FIG. 1 is a schematic diagram of a laser according to an embodiment of the present disclosure; the X-axis in this figure is parallel to the length of the slab gain medium (i.e., the laser transmission direction); the Y axis is parallel to the slab gain medium width; the Z axis is parallel to the height of the slab gain medium;

fig. 2 is a schematic diagram of a slab gain medium and a heat sink copper block included in the holmium laser proposed by the present invention;

fig. 3 is an experimental effect diagram of holmium laser output power variation curves corresponding to different input currents in an experiment of the holmium laser provided by the invention;

fig. 4 is a graph of laser output spectrum effect of laser output power near 17W in an experiment of the holmium laser provided by the invention;

FIG. 5 illustrates an optical system for pump beam shaping in accordance with one embodiment of the present application; a) is a schematic view of a main view; b) is a schematic top view;

FIG. 6 is a schematic diagram of a resonant cavity structure and a pump-mode optical path connection according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram of a resonator structure and a pump optical path connection according to still another embodiment of the present disclosure.

List of parts and reference numerals:

reference numerals	Name of component	Reference numerals	Name of component
				1	Semiconductor pump source	51	Undoped part
11,12	Semiconductor pump light	52	Tm doped moieties
				2	Semiconductor coupling optical fiber	53	Ho doping part
3	Optical shaping system	54	Heat sink body
				31,32,33	Cylindrical mirror	6	Endoscope
4	Endoscope	7	Spectrum filter mirror
				5	Slab gain medium module

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

Referring to fig. 1, the present application provides a laser comprising: the slab gain medium comprises a resonant cavity, a slab gain medium and a pumping source, wherein the pumping source generates pumping light to be coupled with the slab gain medium, and the slab gain medium is arranged in the resonant cavity; the slab gain medium is a uniaxial or biaxial crystal with natural birefringence, and the aspect ratio of any vertical X-axis section is more than 2; the slab gain medium comprises a thulium-doped part and a holmium-doped part which are compounded;

the pump source pumps the thulium-doped part to generate thulium laser confined in the resonant cavity, the thulium laser pumps the holmium-doped part in the same band, and the linearly polarized holmium laser with the wave band of 2.1 mu m is output.

The thulium-doped part absorbs pump light to form population inversion of thulium ions to generate thulium laser, and the thulium laser is pumped in the same band with the holmium-doped part to output holmium laser with a wave band of 2.1 mu m. The slab gain medium with the length-width ratio can realize high power output of 2.1 micron waveband linear polarization Ho laser, and compared with a rod-shaped gain medium with the length-width ratio of 1, the power amplification capacity of the slab gain medium is in direct proportion to the square of the length-width ratio.

Optionally, the pump light is 800nm band pump laser. In the prior art, the output of the high-power Ho laser cannot be directly realized by using 800nm pump light, the laser directly pumps the doping Tm portion by using the 800nm pump light, the use of 1.9 μm laser as the pump light is avoided, and the laser structure is simplified.

Optionally, the pumping source is an optical fiber coupled semiconductor laser, and a circular pumping spot matched with a thulium laser mode in the resonant cavity is formed through an optical shaping system to pump the thulium-doped part of the gain medium.

Optionally, the pump light is shaped into a linear light spot having a length-width ratio equivalent to that of the slab by the high-power semiconductor stacked array through an optical shaping system composed of cylindrical mirrors without being coupled and output by optical fibers, and the thulium-doped part is pumped, so that the pump power bearable by the gain medium can be further improved, and higher linear polarization Ho laser output power can be realized.

In one example, the slab gain media includes: the slab gain medium comprises a first thulium-doped part, a second thulium-doped part and a first holmium-doped part, wherein the first thulium-doped part and the second thulium-doped part are compounded with the first holmium-doped part of the slab gain medium respectively.

In another example, the slab gain media includes: the laser device comprises a first undoped part, a first thulium-doped part and a first holmium-doped part, wherein the first undoped part and the first thulium-doped part are respectively compounded with two opposite end faces of the first holmium-doped part, namely the first undoped part, the first thulium-doped part and the first holmium-doped part are sequentially arranged along the laser transmission direction.

Optionally, the thulium-doped part is a thulium-doped laser gain medium; the holmium-doped part is a holmium-doped laser gain medium; the laser gain medium is a homogeneous laser crystal capable of realizing linear polarization laser output.

Optionally, the method further comprises: a thermal management section, the thermal management section comprising: the heat sink comprises a heat sink body and a plurality of water nozzles, wherein the slab gain medium is clamped in the heat sink body along the transverse direction of the heat sink body; the water nozzle is arranged on the heat sink main body and communicated with the micro-channel in the heat sink main body, and cooling liquid flows in the micro-channel. The thermal management module is used to cool the slat gain medium.

Optionally, the aspect ratio of a cross section of the spot, which is perpendicular to the X axis, after the pump light is shaped is greater than or equal to the aspect ratio of the light passing surface of the slab gain medium;

wherein the direction of the X axis is the laser transmission direction;

and the light passing surface of the slab gain medium is any section of the slab gain medium vertical to the transmission direction of the laser.

Optionally, the resonant cavity includes an output cavity mirror, the output cavity mirror is coated with a film layer having a reflectivity greater than or equal to 99% to the thulium laser and a transmissivity greater than or equal to 99% to the holmium laser.

Optionally, an optical input end of the shaping optical system is connected to the pump source optical path, that is, the pump light is incident into the shaping optical system, and an optical output end of the shaping optical system is connected to the slab gain medium optical path. The pump light is shaped into a required shape through the shaping optical system, which is beneficial to improving the power. The shaping optical system can be obtained by combining various existing optical devices according to shaping requirements.

Example 1

As shown in fig. 1, the present application provides a linearly polarized Ho laser, including: a Tm/Ho composite bonded lath gain medium 5, an endoscope 4, an endoscope 6 and a pumping source 1. The slab gain medium 5 comprises an undoped portion 51, a thulium doped portion 52, and a holmium doped portion 53, and is coated with an evanescent wave protection layer on both largest surfaces. As shown in fig. 2, a Ho-doped portion 53 is provided in the middle portion of the slab gain medium 5, and an undoped portion 51 and a thulium-doped portion 52 are compositely provided on both opposite end faces of the holmium-doped portion 53, respectively. Each section as a whole has a slat structure.

Pump light 11 is emitted by the pump sources 1, respectively, incident on the slab interior from the undoped portion 51 of the slab gain medium 5. The pumping light is uniformly absorbed by the thulium-doped part 52, forms the population inversion of Tm ions, and generates Tm laser confined in the cavity under the action of the resonant cavity mirrors 4 and 6. The Tm laser reciprocates many times inside the slab gain medium 5 to uniformly pump the holmium-doped portion 53, forming a linearly polarized Ho laser output.

The method is essentially different from the existing Tm/Ho composite gain medium, on one hand, the length-width ratio of the lath gain medium is larger than or far larger than that of the existing rod-shaped Tm/Ho composite gain medium (the light-passing surface is circular or square), and the output power of Ho laser is improved; on the other hand, the existing composite gain medium adopts isotropic YAG crystals, and cannot directly realize linear polarization Ho laser output.

As shown in fig. 2, the slab gain medium 5 includes an undoped portion 51, a Tm-doped portion 52, and a Ho-doped portion 53. The composite technology can be gluing technology or diffusion bonding technology. By using the gain medium composite technology, the undoped part 51, the thulium-doped part 52 and the holmium-doped part 53 can be freely selected or arranged, so that the effects of improving the performance of a laser system and relieving the thermal effect of a laser are achieved. For example, the undoped portion 51 is bonded to the front end face of the thulium-doped portion 52, so that the thermal stress of the gain medium under high-power pumping can be relieved, the pumping power that the laser system can bear can be increased, and the output power of the linearly polarized Ho laser can be increased finally.

The thulium-doped portion 52 may be any laser crystal with natural birefringence characteristics capable of producing linearly polarized Tm laser output, such as Tm: YLF, Tm: LuLiF, Tm: YAP, Tm: YAB, Tm: KGW, Tm: GdVO4, and Tm: YVO₄And the Tm ion doping concentration is between 2 and 7 a.t%, and the aspect ratio is more than 2. The Ho-doped part 13 can be any laser crystal with natural birefringence characteristics capable of generating linearly polarized Ho laser output, such as Ho: YLF, Ho: LuLiF, Ho: YAP, Ho: KGW, Ho: YAB, Ho: GdVO₄And Ho: YVO₄Etc., the Ho ion doping concentration is between 0.2 at.% and 1.5 at.%, and the aspect ratio is greater than 2.

Referring to fig. 2, the thermal management section employed in the present application includes: the heat sink body 54, the slab gain medium 5 is inserted in the heat sink body 54 in the transverse direction of the heat sink body 54. Taking a rectangular slab gain medium 5 as an example, the rectangle comprises three dimensions of length, width and height, and the specific dimension of the slab gain medium 5 is 19mm by 6mm by 1.5mm in length, width and height.

The interior of the heat sink body 54 is designed with microchannels (not shown) through which a cooling fluid may flow, as desired. The micro-channel is communicated with an external water nozzle. The external water nozzle is communicated with the temperature control water tank. The water in the tank flows into the heat sink body 54 to temperature control the slab gain medium 5. According to the needs, the temperature of the cooling water in the temperature control water tank is controlled within the range of 5-30 ℃, and the specific numerical value can be selected according to the needs.

In a specific implementation, thermal management is achieved by contact of the gain medium surface perpendicular to the thickness direction of the slab gain medium 5 with the heat sink module 54. To reduce the thermal resistance between the slab gain medium 5 and the heat sink body 54, heat conductive layers made of a metal having good heat conductivity such as indium or gold are provided on the opposite surfaces of the slab gain medium 5 in contact with the heat sink body 54.

The range of the outgoing laser wave band of the pump source used in the application is 760-820 nm, the specific output wavelength is determined by the absorption characteristic of the thulium-doped part, and a person skilled in the art can determine the specific output wavelength according to the material of the used gain medium, for example, aiming at Tm: YLF and Tm: LuLiF crystal, the output wavelength of the pump source can be 792 nm; for YAP crystals, the output wavelength of the pump source may be 795 nm; it can also be 781nm or 808nm far away from Tm-doped part 52 for side-lobe pumping. For YAP crystals, the pump wavelength used in this example was 792 nm.

The pumping source can be a high-power semiconductor laser coupled by an optical fiber, and can also be a high-power LD stacked array integrated by an LD bar. The present embodiment uses a high power fiber-coupled LD as the pump source.

Referring to fig. 1, laser emitted from a pump source is shaped by an optical system 3 to realize the shaping of LD pump light into a circular focusing spot matched with a Tm laser mode in a resonant cavity, and a thulium-doped part 52 is pumped by an undoped part 51. Finally, 2129.54nm (see figure 4) linear polarization Ho laser output of 17.2W (see figure 3) is realized, the laser polarization direction is parallel to the b axis of the YAP crystal, and the polarization extinction ratio is more than 17.2 dB. The output power is nearly 3 times higher than the highest output power (5.96W) of the existing Tm/Ho bonding laser, the output wavelength is further red-shifted to 2130nm on the basis of the laser wavelength of 2122nm of the existing Tm/Ho bonding laser, the cut-off absorption band of an important middle-far infrared nonlinear crystal ZGP can be better kept away, and high-efficiency middle-far infrared laser output is realized; more importantly, the polarized Ho laser output which cannot be achieved by the reported Tm/Ho bonding laser is realized, and the requirements of the industrial information field such as medium and far infrared laser output or high polymer material processing and the like on the laser polarization characteristic can be further met.

Compared with the existing optical fiber coupling end face pumping mode, the mode of direct pumping by adopting the LD stacked array does not need to couple the pumping light generated by the stacked array into the optical fiber through a spatial light path, and then pumping is carried out through the optical fiber, so that the structure is more compact, the use is more economical and convenient, and the hectowatt level pumping power which is difficult to reach by the optical fiber coupling semiconductor laser can be obtained.

Referring to fig. 5a) to b), the pump source outgoing laser is shaped by an optical system composed of a cylindrical mirror 31, a cylindrical mirror 32, and a cylindrical mirror 33, the cylindrical mirror 31, the cylindrical mirror 32, and the cylindrical mirror 33 are all commonly used cylindrical mirrors, the focal lengths of the cylindrical mirror 31 and the cylindrical mirror 33 are 45-55mm, the focal length of the cylindrical mirror 32 is 70-80mm, the cylindrical mirror 31 and the cylindrical mirror 33 reproduce the light emitting length of the stacked array in the slow axis direction, and the focal length of the pump light in the fast axis direction is converged, and finally, a linear pump spot larger than the slab length-width ratio is formed on the end face of the slab gain medium 5 (i.e., the LD stacked array pump light 11 is shaped into a linear light source with the length-width ratio close to or larger than the length-width ratio of the pump end face of the slab gain medium 5), so as to increase the pump power that the slab can bear, and realize higher power output.

Example 2

Another cavity structure and pumping mode of the invention are shown in fig. 6, high power semiconductor stacked pump light is shaped into linear light spots by a cylindrical mirror shaping system, and the high reflection film layers of the pump light 11 and 12 are respectively injected from two ends of the lath, so that the pump light 11 and 12 can be coupled into the lath to respectively pump the thulium-doped parts 52 at two ends of the holmium-doped part 51. In the resonant cavity formed by the cavity mirrors 4,6, the oscillation output of the Ho laser is realized. The resonant cavity structure formed by the cavity mirrors 4 and 6 can be any one of a flat cavity, a flat concave cavity, a concave-convex cavity and the like, and can realize a stable cavity structure for outputting the solid-state laser.

With continued reference to fig. 6, the cavity mirrors 4,6 of the resonant cavity are perpendicular to the laser transmission direction to form a linear cavity. By plating films with high transmission characteristics for the pump light 11 and the pump light 12 with specific incidence angles (the incidence direction and the resonant cavity axis direction form 5-65 degrees) on the two end faces of the slab gain medium, the pump light can be coupled into the slab, the pump light 11 and the pump light 12 are respectively incident into the pump Tm doped part 52 from the two opposite incidence end faces of the slab gain medium 5, and high-power linearly polarized Ho laser output is generated under the action of the cavity mirror 4 and the cavity mirror 6. The resonant cavity structure formed by the cavity mirrors 4 and 6 can be any one of a flat cavity, a flat concave cavity, a concave-convex cavity and the like, and can realize a stable cavity structure for outputting the solid-state laser.

Example 3

Another cavity structure and pumping mode of the present application is shown in fig. 7, where cavity mirrors 4 and 6 of the resonant cavity are parallel to the laser transmission direction to form a folded cavity. The laser includes: the pump lights 11 and 12 which are arranged opposite to the light incident end face of the slab gain medium 5 and emit light perpendicular to the light incident end face are symmetrically arranged on two sides, only one side is described, and the other side is the same. The pumping light 11,12 is pumped into the slab gain medium 5 through the spectrum filter mirror 7, and the spectrum filter mirror 7 also plays a role of turning and emitting laser, and the resonant cavity structure can be realized by a folding cavity except a linear cavity. The used cavity mirrors 4,6 and 7 have a reflection effect on the Tm laser, so that the Tm laser is prevented from being leaked.

Like a myriawatt-level Yb laser or a myriawatt-level Nd laser, by virtue of the excellent thermal management capability of the slab structure, the linear polarization Ho laser output of a hectowatt level can be realized from a Tm/Ho bonding slab structure under the LD cascade pumping power which cannot be reached by the conventional fiber coupling LD.

Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.