CN110323671B

CN110323671B - Single-mode semiconductor laser epitaxial structure based on photonic crystal control

Info

Publication number: CN110323671B
Application number: CN201910322368.2A
Authority: CN
Inventors: 郑婉华; 陈忠浩; 周旭彦; 渠红伟; 齐爱谊
Original assignee: Institute of Semiconductors of CAS
Current assignee: Institute of Semiconductors of CAS
Priority date: 2019-04-19
Filing date: 2019-04-19
Publication date: 2021-05-11
Anticipated expiration: 2039-04-19
Also published as: CN110323671A

Abstract

A single mode semiconductor laser epitaxial structure based on photonic crystal control, comprising: the N-type substrate layer is used for growing epitaxial materials; the N-type limiting layer is arranged on the N-type substrate layer and used for limiting the expansion of the optical field to the N-type region; the photonic crystal is configured on the N-type limiting layer and used for regulating and controlling an output light field mode; an active region disposed on the photonic crystal; the P-type limiting layer is configured on the active region and used for limiting the expansion of the optical field to the P-type region; the P-type cover layer is configured on the P-type limiting layer and used for limiting an optical field and reducing a carrier potential barrier; and the P-type contact layer is arranged on the P-type cover layer and is used for forming ohmic contact with the metal.

Description

Single-mode semiconductor laser epitaxial structure based on photonic crystal control

Technical Field

The invention relates to the field of high-performance lasers, in particular to a single-mode semiconductor laser epitaxial structure based on photonic crystal control.

Background

The semiconductor laser has the advantages of small output volume, light weight, high pumping efficiency and the like, and particularly has great advantages in the aspects of high efficiency and high-power laser output coupling of the semiconductor edge-emitting laser.

However, the output power of the monotube of the semiconductor laser is not high, wherein the damage of the cavity surface film is easily caused mainly because the light-emitting area of the semiconductor laser is small and the optical power density is high, so how to increase the monotube output power of the semiconductor laser is a crucial aspect of how to increase the mode volume of the semiconductor laser and make the monotube obtain a higher damage threshold.

In order to increase the mode volume of a semiconductor laser, the mode needs to be fully expanded in the epitaxial direction, the traditional mode is that a large optical cavity structure is used for increasing the thickness in the epitaxial direction, the mode expansion effect of the large optical cavity structure is weaker along with the increase of the epitaxial thickness, the mode limiting factor is lower, and the mode volume cannot be expanded infinitely; and then, a photonic crystal structure is developed and used, the photonic crystal structure has the function of controlling the mode, and different photonic crystal structures can be designed to control the mode output. The prior art proposes an epitaxial photonic crystal structure, in which the waveguide is formed by a one-dimensional photonic crystal and the quantum well is located in a high refractive index material layer of the photonic crystal. In the structure, the fundamental transverse mode can be expanded in the whole photonic crystal structure, and the strongest position of the near-field distribution of the fundamental transverse mode is superposed with the quantum well, so that the high limiting factor of the fundamental mode is ensured. The high-order mode is mainly distributed in the whole photonic crystal, the superposition with the quantum well is less, and the limiting factor is lower. And a larger limiting factor difference exists between the fundamental transverse mode and the high-order mode, so that the fundamental transverse mode lasing can be effectively ensured. However, the structure can only realize fundamental transverse mode lasing, and cannot realize first-order mode, second-order mode or higher-order mode lasing.

Disclosure of Invention

Technical problem to be solved

The invention provides a photonic crystal control-based single-mode semiconductor laser epitaxial structure, which aims to solve the problem of single control of laser output spatial mode.

(II) technical scheme

According to one aspect of the invention, a single-mode semiconductor laser epitaxial structure based on photonic crystal control is provided, which comprises an N-type substrate layer for growing epitaxial materials; the N-type limiting layer is arranged on the N-type substrate layer and used for limiting the expansion of the optical field to the N-type region; the photonic crystal is configured on the N-type limiting layer and used for regulating and controlling an output light field mode; an active region disposed on the photonic crystal; the P-type limiting layer is configured on the active region and used for limiting the expansion of the optical field to the P-type region; the P-type cover layer is configured on the P-type limiting layer and used for limiting an optical field and reducing a carrier potential barrier; and the P-type contact layer is arranged on the P-type cover layer and is used for forming ohmic contact with the metal.

In a further scheme, the photonic crystal is a one-dimensional photonic crystal and comprises a periodic and quasi-periodic structure with high refractive index and low refractive index which are formed by modulating material components.

In a further aspect, the material of the N-type substrate layer includes GaN, GaAs, InP, or GaSb.

In a further embodiment, the wavelength of the material of the N-type substrate layer is in the range of 10nm to 14 μm.

In a further aspect, the active region comprises a single quantum well, a multiple quantum well, a quantum dot, or a superlattice structure.

In a further embodiment, the number of photonic crystal periods is 3 to 20.

In a further aspect, the photonic crystal has a thickness of 2 μm to 50 μm.

(III) advantageous effects

According to the technical scheme, the single-mode semiconductor laser epitaxial structure based on photonic crystal control provided by the invention at least has the following beneficial effects:

the mode of laser output can be controlled by adjusting the thickness, refractive index and components of the photonic crystal epitaxial structure, so that the photonic crystal epitaxial structure can output first-order mode, second-order mode or higher-order mode laser besides basic transverse mode laser.

The mode volume in the epitaxial direction is expanded, the power density is reduced under the same power, and the laser can obtain a higher damage threshold value, so that the output power of the semiconductor laser is improved.

Due to the larger mode expansion, the coupling efficiency is higher than that of the traditional coupling by using evanescent waves, and the coupling efficiency of the laser to the waveguide can be improved.

Drawings

Fig. 1 is a schematic view of an epitaxial structure of a single-mode semiconductor laser based on photonic crystal control according to an embodiment of the present invention.

FIG. 2 is a diagram of theoretical calculation output of the basilar membrane of an embodiment of the present invention.

FIG. 3 is a graph of the theoretical calculation output of the first order mode of the present invention.

FIG. 4 is a second order theoretical model calculation output diagram according to an embodiment of the present invention.

Fig. 5 is a diagram of theoretical calculation output of the far-field divergence angle of the fundamental mode according to the embodiment of the present invention.

FIG. 6 is a diagram of the first-order far-field divergence angle theoretical calculation output of an embodiment of the present invention.

Fig. 7 is a diagram of the second-order mode far-field divergence angle theoretical calculation output of the embodiment of the present invention.

FIG. 8 is a graph of output power current voltage obtained from the base film and first-order mode experiments according to an embodiment of the present invention.

Fig. 9 is a far field divergence angle plot from a basement membrane experiment of an embodiment of the invention.

Fig. 10 is a far field divergence angle plot from a first order mode experiment of an embodiment of the present invention.

[ legends of drawings ]

1. An N-type substrate layer; 2. an N-type confinement layer; 3. a photonic crystal;

4. an active region; 5. a P-type confinement layer; 6. a P-type cap layer; 7. p-type contact layer

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

In an embodiment of the present invention, a single-mode semiconductor laser epitaxial structure based on photonic crystal control is provided, and fig. 1 is a schematic view of a single-mode semiconductor laser epitaxial structure based on photonic crystal control according to an embodiment of the present invention, as shown in fig. 1, including an N-type substrate layer 1 for growing an epitaxial material; the N-type limiting layer 2 is arranged on the N-type substrate layer 1 and used for limiting the expansion of an optical field to an N-type region; the photonic crystal 3 is configured on the N-type limiting layer 2 and used for regulating and controlling an output light field mode; an active region 4 disposed on the photonic crystal 3 as an active light emitting material; a P-type confinement layer 5 disposed above the active region 4 for confining the expansion of the optical field to the P-type region; a P-type cap layer 6 disposed on the P-type confinement layer 5 for confining the optical field and reducing the carrier barrier; and the P-type contact layer 7 is arranged on the P-type cover layer 6 and is used for forming ohmic contact with metal.

In one embodiment, the photonic crystal 3 may be a one-dimensional photonic crystal, which includes a periodic and quasi-periodic structure with high and low refractive indexes being formed by modulating material components, the number of the periods is 3 to 20, and the thickness is 2 μm to 50 μm, and the thickness, the refractive index and the composition of the photonic crystal 3 may be configured according to settings for outputting different optical field modes.

In one embodiment, the material of the N-type substrate layer 2 may include GaN, GaAs, InP, or GaSb, the wavelength range is 10nm to 14 μm, and the active region 4 includes a single quantum well, a multiple quantum well, a quantum dot, or a superlattice structure.

Fig. 2 is a diagram of theoretical calculation output of the basilar membrane according to the embodiment of the present invention, as shown in fig. 2, with the abscissa representing the position in the epitaxial direction and the ordinate representing the normalized intensity of the light field. Wherein the restriction factor of the basal lamina is 1.34%, the largest of all mode restriction factors; the limiting factor for the first order mode is 0.21%; the second order mode limiting factor is 0.38%; the third order mode limiting factor is 0.39%; the confinement factor for the higher-order modes is significantly lower than that for the fundamental mode, so the laser is primarily lasing of the basement membrane.

Fig. 3 is a graph of the first-order mode theoretical calculation output of the embodiment of the present invention, as shown in fig. 3, with the abscissa representing the position in the epitaxial direction and the ordinate representing the normalized intensity of the light field. Wherein the limiting factor for the first order mode is 1.59%, which is the largest of all mode limiting factors; restriction factor of basement membrane 0.17%; the second order mode limiting factor is 0.13%; the third order mode limiting factor is 0.53%; the confinement factor for the other modes is significantly lower than that of the first-order mode, so the laser is primarily first-order mode lasing.

Fig. 4 is a diagram of the second-order mode theoretical calculation output of the embodiment of the present invention, as shown in fig. 4, the abscissa is the position in the epitaxial direction, and the ordinate is the normalized intensity of the light field. Wherein the limiting factor of the second order mode is 1.63%, which is the largest of all mode limiting factors; restriction factor of basement membrane 0.19%; the first order mode limiting factor is 0.07%; the third order mode limiting factor is 0.43%; the confinement factor for the other modes is significantly lower than that of the second order mode, so the laser is primarily lasing in the second order mode.

Fig. 5 is a diagram of theoretical calculation output of the far-field divergence angle of the fundamental mode according to the embodiment of the present invention, as shown in fig. 5, with the abscissa representing the far-field divergence angle and the ordinate representing the intensity normalized by the light field. It can be seen from fig. 5 that the basal lamina far field is a single lobe output with a divergence angle of 10 ° full width at half maximum.

Fig. 6 is a diagram of the theoretical calculation output of the far-field divergence angle in the first-order mode according to the embodiment of the present invention, as shown in fig. 6, the abscissa is the far-field divergence angle, and the ordinate is the intensity normalized by the light field. It can be seen from the figure that the far field of the first-order mode is double-peak output, the two peaks are symmetrically distributed, and the divergence angle full width at half maximum of each peak is 9 degrees.

Fig. 7 is a diagram of the second-order mode far-field divergence angle theoretical calculation output according to the embodiment of the present invention, as shown in fig. 7, the abscissa is the far-field divergence angle, and the ordinate is the intensity of the light field normalization. It can be seen from fig. 7 that the second-order mode far field is also a double-peak output, but the position of the second-order mode far field is different from that of the first-order mode far field, the two peaks are further away from the central coordinate point and are symmetrically distributed, and the half maximum width of the divergence angle of each peak is 9 degrees.

Fig. 8 is a current-voltage diagram of output power obtained by a base film and a first-order mode experiment according to an embodiment of the present invention, as shown in fig. 8, an abscissa is a laser current value, a left ordinate is a voltage value applied to the laser, a right coordinate is an output power value, a dotted line is a performance curve of the base-mode output semiconductor laser, and a solid line is a performance curve of the first-order mode output semiconductor laser.

Fig. 9 is a far field divergence angle diagram obtained by the basement membrane experiment of the embodiment of the invention, as shown in fig. 9, the abscissa is the far field divergence angle, and the ordinate is the intensity normalized by the light field, and the basic and simulation approximation can be seen by comparing with the simulation, and the experiment is identical with the theory.

Fig. 10 is a far field divergence angle diagram obtained by a first-order mode experiment of the embodiment of the invention, as shown in fig. 10, the abscissa is the far field divergence angle, and the ordinate is the normalized intensity of the light field, and the basic and simulation approximation can be seen by comparing with the simulation result, and the experiment is matched with the theory.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A single mode semiconductor laser epitaxial structure based on photonic crystal control, comprising:

the N-type substrate layer is used for growing epitaxial materials;

the N-type limiting layer is arranged on the N-type substrate layer and used for limiting the expansion of the optical field to the N-type region;

the photonic crystal is configured on the N-type limiting layer and used for regulating and controlling an output light field mode;

an active region disposed on the photonic crystal;

the P-type limiting layer is configured on the active region and used for limiting the expansion of the optical field to the P-type region;

the P-type cover layer is configured on the P-type limiting layer and used for limiting an optical field and reducing a carrier potential barrier;

the P-type contact layer is arranged on the P-type cover layer and is used for forming ohmic contact with metal;

the mode of laser output is controlled by adjusting the thickness, the refractive index and the components of the photonic crystal epitaxial structure, so that the photonic crystal epitaxial structure can output first-order mode, second-order mode or higher-order mode laser besides basic transverse mode laser;

when the output light field mode is a first-order mode, the limiting factor of the first-order mode is the maximum limiting factor of all the modes;

and when the output light field mode is a second-order mode, the limiting factor of the second-order mode is the largest of all mode limiting factors.

2. The structure of claim 1, wherein the photonic crystal is a one-dimensional photonic crystal comprising a periodic or quasi-periodic structure of abrupt high and low refractive index or gradual change formed by material composition modulation.

3. The structure of claim 1 wherein the material of the N-type substrate layer comprises GaN, GaAs, InP, or GaSb.

4. The structure of claim 1 wherein the N-type substrate layer has a material wavelength in the range of 10nm to 14 μm.

5. The structure of claim 1, wherein the active region comprises a single quantum well, a multiple quantum well, a quantum dot, or a superlattice structure.

6. The structure of claim 2 wherein the number of photonic crystal periods is from 3 to 20.

7. The structure of claim 1 wherein the photonic crystal is 2 μm to 50 μm thick.