阅读说明：本技术 一种基于微纳结构半导体薄膜的增益装置及激光器 (Gain device based on micro-nano structure semiconductor thin film and laser ) 是由 崔文达 韩凯 王红岩 杨子宁 宋长青 华卫红 许晓军 于 2020-04-29 设计创作，主要内容包括：本发明公开一种基于微纳结构半导体薄膜的增益装置及激光器,该微纳结构半导体薄膜自上而下包括窗口层(223)、微结构层(221)和多量子阱层(222)；所述多量子阱层(222)包括至少两层势垒层,不同所述势垒层之间包括阱层；所述势垒层和所述阱层分别由不同半导体材料制备而成；该增益装置包括棱镜窗口(21)和所述微纳结构半导体薄膜(22)；该激光器包括至少一个有源镜(2),有源镜(2)包括所述增益装置、基底(23)、热沉(24)和聚焦透镜(25)。本发明提供的激光器能够在高功率条件下实现高效率、高光束质量的输出。(The invention discloses a gain device and a laser based on a micro-nano structure semiconductor film, wherein the micro-nano structure semiconductor film comprises a window layer (223), a micro-structure layer (221) and a multi-quantum well layer (222) from top to bottom; the MQW layer (222) comprises at least two barrier layers, and the barrier layers are different from each other in that a well layer is included; the barrier layer and the well layer are respectively prepared from different semiconductor materials; the gain device comprises a prism window (21) and the micro-nano structure semiconductor film (22); the laser comprises at least one active mirror (2), the active mirror (2) comprising said gain means, a substrate (23), a heat sink (24) and a focusing lens (25). The laser provided by the invention can realize high-efficiency and high-beam-quality output under the condition of high power.)

1. The micro-nano structure semiconductor film is characterized by comprising a window layer (223), a micro-structure layer (221) and a multi-quantum well layer (222) from top to bottom;

the multi-quantum well layer (222) comprises at least two barrier layers which are stacked up and down and at least one well layer, wherein the well layer is positioned between different barrier layers; the barrier layer and the well layer are respectively made of different semiconductor materials.

2. A micro-nano structured semiconductor film according to claim 1, wherein the micro-structured layer (221) is a one-dimensional grating structure.

3. The micro-nano structure semiconductor film according to claim 2, wherein the period of the micro-structure layer (221) is 0- λ/n, the duty ratio is 0.01-0.99, and the etching depth is 0- λ/n, wherein λ is the laser wavelength, and n is the medium refractive index.

4. The micro-nano structure semiconductor film according to claim 1, wherein the thickness of the barrier layer is 0- λ/2n, λ is the wavelength of laser, and n is the refractive index of the medium; the thickness of the well layer is 5-15 nm.

5. The micro-nano structure semiconductor film according to claim 1, wherein the thickness of the window layer (223) is 0- λ/10n, λ is the laser wavelength, and n is the medium refractive index.

6. A gain device based on a micro-nano structure semiconductor film is characterized by comprising a prism window (21) and the micro-nano structure semiconductor film (22) according to any one of claims 1-5;

the prism window (21) includes a bottom surface (213) and at least one pair of inclined surfaces inclined with respect to the bottom surface; the pair of inclined surfaces are symmetrically distributed on the bottom surface (213), and the inclination angles are respectively more than +0 degrees, less than +90 degrees, more than-0 degrees and less than-90 degrees; the inclined surfaces are plated with a group of film systems to achieve the purposes of reflecting the pump light and transmitting the oscillation light;

at least the upper end of the micro-nano structure semiconductor film (22) is fixedly connected with the bottom surface (213) of the prism window (21);

and pumping light enters the prism window (21) from the side edge of the micro-nano structure semiconductor film (22) to be vertical to the bottom surface (213), and enters the micro-nano structure semiconductor film (22) from the window layer (223) for gain after being totally reflected by the inclined surface.

7. The gain device based on the micro-nano structure semiconductor thin film according to claim 6, wherein the film system comprises a plurality of layers of pump light high-reflection films and a plurality of layers of oscillation light high-transmission films, the reflectivity of the pump light high-reflection films is greater than 99.9%, and the transmissivity of the oscillation light high-transmission films is greater than 99.9%.

8. A laser based on a micro-nano structure semiconductor film is characterized by comprising:

active mirror group comprising at least one active mirror (2), the active mirror (2) comprising a gain device according to claim 6, a substrate (23), a heat sink (24) and a focusing lens (25); one end of the substrate (23) is fixedly connected with the lower end of the micro-nano structure semiconductor film (22), and the other end of the substrate (23) is fixedly connected to the heat sink (24); the focusing lens (25) is distributed on the side edge of the substrate (23) and fixed on the heat sink (24), and the pumping light enters the prism window (21) through the focusing lens (25) and is vertical to the bottom surface of the prism window (21);

when the number of the active mirrors (2) in the active mirror group is 2, the active mirrors (2) are arranged in a staggered and opposite manner, and when the number of the active mirrors (2) in the active mirror group is more than or equal to 3, the active mirrors (2) are arranged in a zigzag manner, so that the oscillating light transmitted from one active mirror (2) can enter the adjacent active mirror (2) at the same incident angle;

the active lens comprises a total reflection mirror (3) and a coupling output mirror (4), wherein the total reflection mirror (3) and the coupling output mirror (4) are symmetrically distributed on two sides of the active lens group;

the active mirror group, the total reflection mirror (3) and the coupling output mirror (4) jointly form a resonant cavity;

at least one pump source (1) for providing pump light.

9. The laser based on the micro-nano structure semiconductor film according to claim 8, wherein the substrate (23) is made of a high thermal conductivity material, and the thermal conductivity is more than 500W/m-K.

10. The laser based on the micro-nano structure semiconductor film according to claim 8, wherein the pump source (1) is a semiconductor pump source.

Technical Field

The invention relates to the technical field of lasers, in particular to a gain device based on a micro-nano structure semiconductor film and a laser.

Background

An optically pumped solid state laser is one of the main lasers currently realizing high power and high efficiency output. At present, the main bottleneck restricting further improvement of the power and the beam quality of the solid laser is waste heat generated in the operation process of the laser, and the waste heat can cause adverse effects such as thermal lens, depolarization, birefringence, thermal stress and the like in a solid medium, so that the power, the efficiency and the beam quality of the laser are reduced, and therefore, the improvement of the heat dissipation efficiency of the laser is the key point for breaking through the improvement of the power of the high-energy solid laser.

Semiconductor thin film lasers are one of the effective solutions for achieving efficient heat dissipation. In one aspect, the semiconductor thin film is a semiconductor gain medium having a thickness on the order of microns or nanometers, such as GaN, GaAs, GaSb, and InP. These semiconductor materials have extremely high absorption and gain coefficients, and have the potential to achieve effective absorption of pump light and effective gain of laser light in micron-sized thicknesses. On the other hand, based on a mature semiconductor growth technology, the transverse size of the semiconductor film can reach millimeter to centimeter magnitude, so that the gain medium has extremely high specific surface area, and the whole gain structure can realize extremely high heat dissipation efficiency.

At present, most high-power semiconductor lasers are electrically excited edge-emitting lasers, the electro-optic conversion efficiency of the lasers can reach about 70%, but high-beam-quality output cannot be realized due to the large divergence angle of the edge-emitting lasers, and the Vertical External Cavity Surface Emitting Laser (VECSEL) adopting reflection type light emitting can realize high-beam-quality and large-mode-field laser. However, the laser cannot achieve high power output at present, the main limiting factor is still the influence of the thermal effect, and waste heat generated by the semiconductor gain layer under the high-power operating condition cannot be quickly led out through the heat sink, so that the output power and the efficiency of the laser are influenced. Removing the Distributed Bragg Reflector (DBR) layer in such a laser is an effective way to improve the heat dissipation efficiency, but after removing the DBR layer, the total reflection of the laser light perpendicular to the surface of the gain medium cannot be solved well. In summary, further improving the heat dissipation efficiency of the semiconductor gain film, solving the total reflection problem of VECSEL without DBR layer is the key to realizing a laser with high efficiency and high beam quality output under high power condition.

Disclosure of Invention

The invention provides a gain device based on a micro-nano structure semiconductor film and a laser, which are used for improving the heat dissipation efficiency of a VECSEL laser in the prior art and realizing reflective light emission without a DBR layer so as to obtain laser output with high efficiency and high beam quality.

In order to achieve the above purpose, the present invention provides a micro-nano structure semiconductor film, which comprises, from top to bottom, a window layer 223, a micro-structure layer 221, and a multi-quantum well layer 222;

the MQW layer 222 comprises at least two barrier layers stacked up and down and at least one well layer, wherein the well layer is positioned between different barrier layers; the barrier layer and the well layer are respectively made of different semiconductor materials.

Preferably, the microstructure layer 221 is a one-dimensional grating structure.

Preferably, the period of the microstructure layer 221 is 0 to λ/n (λ/n represents λ divided by n), the duty ratio is 0.01 to 0.99, and the etching depth is 0 to λ/n, where λ is the wavelength of the laser and n is the refractive index of the medium.

Preferably, the thickness of the barrier layer is 0-lambda/2 n (lambda/2 n represents lambda divided by 2 n), lambda is the laser wavelength, and n is the medium refractive index; the thickness of the well layer is 5-15 nm.

Preferably, the thickness of the window layer 223 is 0- λ/10n (λ/10n represents λ divided by 10 n), λ is the laser wavelength, and n is the medium refractive index.

In order to achieve the above object, the present invention further provides a gain device based on a micro-nano structure semiconductor thin film, which includes a prism window 21 and the micro-nano structure semiconductor thin film 22;

the prism window 21 includes a bottom surface 213 and at least one pair of inclined surfaces inclined with respect to the bottom surface; the pair of inclined surfaces are symmetrically distributed on the bottom surface 213, and the inclined angles are respectively greater than +0 degrees, less than +90 degrees, greater than-0 degrees and less than-90 degrees; the inclined surfaces are plated with a group of film systems to achieve the purposes of reflecting the pump light and transmitting the oscillation light;

at least the upper end of the micro-nano structure semiconductor film 22 is fixedly connected with the bottom surface 213 of the prism window 21;

the pumping light enters the prism window 21 from the side edge of the micro-nano structure semiconductor film 22 to be vertical to the bottom surface 213, and after being totally reflected by the inclined surface, the pumping light enters the micro-nano structure semiconductor film 22 from the window layer 223 for gain.

Preferably, the film system comprises a plurality of layers of pump light high-reflection films and a plurality of layers of oscillation light high-transmission films, wherein the reflectivity of the pump light high-reflection films is greater than 99.9%, and the transmissivity of the oscillation light high-transmission films is greater than 99.9%.

In order to achieve the above object, the present invention further provides a laser based on a micro-nano structure semiconductor thin film, including:

an active mirror group comprising at least one active mirror 2, said active mirror 2 comprising a gain device as described above, a substrate 23, a heat sink 24 and a focusing lens 25; one end of the substrate 23 is fixedly connected with the lower end of the micro-nano structure semiconductor film 22, and the other end of the substrate 23 is fixedly connected to the heat sink 24; the focusing lens 25 is distributed on the side of the substrate 23 and fixed on the heat sink 24, and the pumping light enters the prism window 21 through the focusing lens 25 and is perpendicular to the bottom surface 213 of the prism window 21;

when the number of the active mirrors 2 in the active mirror group is 2, the active mirrors 2 are arranged in a staggered and opposite manner, and when the number of the active mirrors 2 in the active mirror group is more than or equal to 3, the active mirrors 2 are arranged in a zigzag manner, so that the oscillating light transmitted from one active mirror 2 can enter the adjacent active mirrors 2 at the same incident angle;

the fully-reflecting mirror 3 and the coupling output mirror 4 are symmetrically distributed on two sides of the active mirror group;

the active lens group, the total reflection lens 3 and the coupling output lens 4 form a resonant cavity together;

at least one pump source 1 for providing pump light.

Preferably, the substrate 23 is made of a high thermal conductivity material, and the thermal conductivity is more than 500W/m.K.

Preferably, the pump source 1 is a semiconductor pump source, and the pumping mode is distributed pumping.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the laser based on the micro-nano structure semiconductor film, the DBR layer of the traditional OPSL is removed, the heat dissipation efficiency can be effectively improved, the limitation of the thermal effect on the power improvement of the optical pump semiconductor laser is reduced, and high-power output can be realized.

2. According to the laser based on the micro-nano structure semiconductor film, the high reflection of pumping light and oscillation light is realized through the micro-structure design of the semiconductor gain film, meanwhile, the local enhancement of the light field is realized in the micro-nano structure semiconductor film, and the well layer and the barrier layer in the micro-nano structure semiconductor film can be positioned at the light field enhancement position, so that the higher one-way gain and the lower pumping threshold value are realized, the laser efficiency is improved, and the laser output with high beam quality and large mode field is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a micro-nano structure semiconductor film provided in embodiment 1 of the present invention;

fig. 2 is a schematic structural diagram of a gain device based on a micro-nano structure semiconductor thin film according to embodiment 2 of the present invention;

fig. 3 is a schematic structural diagram of a laser based on a micro-nano structure semiconductor film provided in embodiment 3 of the present invention;

FIG. 4 is a graph showing the reflectivity distribution of the active mirror under different incident angles in example 3 of the present invention;

fig. 5 is a light field distribution diagram of the pump light and the oscillation light in the micro-nano structure semiconductor film in embodiment 3 of the present invention.

The reference numbers illustrate: 1: a pump source; 2: an active mirror; 21: a prism window; 211: a first inclined surface; 212: a second inclined surface; 213: a bottom surface; 22: a micro-nano structure semiconductor film; 221: a microstructure layer; 222: a multiple quantum well layer; 223: a window layer; 23: a substrate; 24: a heat sink; 25: a focusing lens; 3: a total reflection mirror; 4: an output mirror is coupled.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides a micro-nano structure semiconductor film which comprises a window layer 223, a micro-structure layer 221 and a multi-quantum well layer 222 from top to bottom;

the MQW layer 222 comprises at least two barrier layers stacked up and down and at least one well layer, wherein the well layer is positioned between different barrier layers; the barrier layer and the well layer are respectively made of different semiconductor materials.

The design of the micro-nano structure semiconductor film belongs to the design of a micro-nano structure, and the local enhancement of a gain layer (a well layer and a barrier layer) of a light field in the micro-nano structure semiconductor film is realized through the micro-nano structure design, so that higher one-way gain and lower pumping threshold are realized, and high reflection or high transmittance of pumping light and intracavity oscillation light can be realized.

Preferably, the microstructure layer 221 is a one-dimensional grating structure to realize a high reflection function of the micro-nano structure semiconductor film.

Preferably, the period of the microstructure layer 221 is 0- λ/n, the duty ratio is 0.01-0.99, and the etching depth is 0- λ/n, where λ is the wavelength of the laser and n is the refractive index of the medium. The microstructure layer 221 is optimally designed to better realize the high reflection function of the micro-nano structure semiconductor film.

Preferably, the thickness of the barrier layer is 0-lambda/2 n, lambda is laser wavelength, and n is medium refractive index; the thickness of the well layer is 5-15 nm. The thicknesses of the barrier layer and the well layer are related to the materials used by the barrier layer and the well layer, and the thicknesses are designed according to the materials of the barrier layer and the well layer so as to ensure that the micro-nano structure semiconductor film has a high reflection function.

Preferably, the thickness of the window layer 223 is 0- λ/10n, λ is the laser wavelength, and n is the medium refractive index. The window layer 223 is used for protecting the microstructure layer 221, and the thickness of the window layer 223 is controlled to achieve a better protection effect on the microstructure layer 221 without affecting the high reflection function of the micro-nano structure semiconductor film.

The invention also provides a gain device based on the micro-nano structure semiconductor film, which comprises a prism window 21 and the micro-nano structure semiconductor film 22;

the prism window 21 includes a bottom surface 213 and at least one pair of inclined surfaces inclined with respect to the bottom surface; the pair of inclined surfaces are symmetrically distributed on the bottom surface 213, and the inclined angles are respectively greater than +0 degrees, less than +90 degrees, greater than-0 degrees and less than-90 degrees; the inclined surfaces are plated with a group of film systems to achieve the purposes of reflecting the pump light and transmitting the oscillation light;

at least the upper end of the micro-nano structure semiconductor film 22 is fixedly connected with the bottom surface 213 of the prism window 21;

and pumping light enters the prism window 21 from the side edge of the micro-nano structure semiconductor film 22 to be vertical to the bottom surface, and enters the micro-nano structure semiconductor film 22 from the window layer 223 for gain after being totally reflected by the inclined surface.

Preferably, the film system comprises a plurality of layers of pump light high-reflection films and a plurality of layers of oscillation light high-transmission films, wherein the reflectivity of the pump light high-reflection films is greater than 99.9%, and the transmissivity of the oscillation light high-transmission films is greater than 99.9%. The high reflection films of different pump lights can realize high reflection of the pump lights with different wavelengths and incidence angles; the high-transmittance film for the oscillation light can realize high transmittance for the oscillation light with different wavelengths. While a high reflectivity or transmittance of the film reduces light loss.

Preferably, the upper end of the micro-nano structure semiconductor film 22 is attached to the bottom surface of the prism window 21 by a photoresist technology, so that the heat dissipation efficiency of the micro-nano structure semiconductor film 22 is improved.

The invention also provides a laser based on the micro-nano structure semiconductor film, which comprises the following components:

an active mirror group comprising at least one active mirror 2, said active mirror 2 comprising a gain device as described above, a substrate 23, a heat sink 24 and a focusing lens 25; one end of the substrate 23 is fixedly connected with the lower end of the micro-nano structure semiconductor film 22, and the other end of the substrate 23 is fixedly connected to the heat sink 24; the focusing lens 25 is distributed on the side of the substrate 23 and fixed on the heat sink 24, and the pumping light enters the prism window 21 through the focusing lens 25 and is perpendicular to the bottom surface 213 of the prism window 21;

when the number of the active mirrors 2 in the active mirror group is 2, the active mirrors 2 are arranged in a staggered and opposite manner, and when the number of the active mirrors 2 in the active mirror group is more than or equal to 3, the active mirrors 2 are arranged in a zigzag manner, so that the oscillating light transmitted from one active mirror 2 can enter the adjacent active mirrors 2 at the same incident angle;

the fully-reflecting mirror 3 and the coupling output mirror 4 are symmetrically distributed on two sides of the active mirror group;

the active lens group, the total reflection lens 3 and the coupling output lens 4 form a resonant cavity together;

at least one pump source 1 for providing pump light.

The active mirror group, the total reflection mirror 3 and the coupling output mirror 4 jointly form a resonant cavity, through the structural design of the micro-structure layer 221, oscillation light generated in the micro-nano structure semiconductor film 22 is totally reflected at the junction of the substrate 23 and the micro-nano structure semiconductor film 22, and meanwhile, the oscillation light generates a local field enhancement in the multi-quantum well layer 222, so that the efficiency of the laser can be effectively improved;

in the operation process of the laser, the oscillation light is subjected to gain amplification while generating total reflection in the plurality of active mirrors 2, total reflection is generated at the total reflection mirror 3, and partial reflection is generated at the coupling output mirror 4; further, the reflectivity of the total reflection mirror 3 to the oscillation light is more than 99.9%; further, the reflectivity of the coupling output mirror 4 is greater than 0 and less than 99%; after going back and forth in the resonant cavity, the oscillation light is amplified by gain, and finally the laser is output at the coupling output mirror 4.

The number of the active mirrors 2 in the active mirror group is set according to actual use requirements, and the more the number of the active mirrors 2 is, the better the gain effect on laser is. The number of pump sources 1 is set according to the number of active mirrors 2, each active mirror 2 corresponding to a group of pump sources 1.

Preferably, the active mirrors 2 in the active mirror group are all reflective, that is, the oscillating light is totally reflected at the micro-nano structure semiconductor film, so as to form a resonant cavity among the active mirror group, the total reflection mirror 3 and the coupling output mirror 4.

Preferably, the substrate 23 is made of a high thermal conductivity material, and the thermal conductivity is more than 500W/m.K. The substrate 23 serves as a heat sink layer for the laser of the present invention, and a material with high thermal conductivity is selected to improve the heat dissipation efficiency of the laser.

Preferably, the substrate 23 is machined to have a surface with a set curvature to make a concave or convex active mirror to increase the range of applications of the laser of the present invention.

Preferably, the pump source 1 is a semiconductor pump source, and the pumping mode is distributed pumping. A suitable pump source is selected to provide high quality pump light. Distributed pumping namely: each active mirror 2 corresponds to a group of pump sources (one focusing lens corresponds to one pump source), and the heat dissipation pressure of each active mirror can be effectively reduced. The pumping light enters the prism window 21 from the bottom surface 213, is totally reflected by the first inclined surface 211 and the second inclined surface 212 and then is incident into the micro-nano structure semiconductor film 22, and the pumping light is modulated by the micro-structure layer 221 and generates a local optical field enhancement in the multi-quantum well layer 222, so that the absorption rate of the pumping light is improved.

Preferably, a position of the bottom surface of the prism window 21 corresponding to the focusing lens 25 (i.e., a position where the pump light is incident) is coated with a pump light high-transmittance film (preferably, a high-transmittance film having a wavelength of 960 nm and an incident angle of 0 degree) to increase the transmittance of the pump light.

The semiconductor thin film laser provided by the invention removes the traditional DBR (distributed Bragg reflector) layer, and is replaced by a specially designed micro-nano structure to realize high reflection and optical field local enhancement, so that higher heat dissipation efficiency and large-mode field output are realized. The semiconductor film provided by the invention provides an effective solution for realizing a high-power and high-beam-quality solid laser.