CN111952837A - Coupling output structure of terahertz quantum cascade laser and packaging method thereof - Google Patents
Coupling output structure of terahertz quantum cascade laser and packaging method thereof Download PDFInfo
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- CN111952837A CN111952837A CN202010800920.7A CN202010800920A CN111952837A CN 111952837 A CN111952837 A CN 111952837A CN 202010800920 A CN202010800920 A CN 202010800920A CN 111952837 A CN111952837 A CN 111952837A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/3401—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers
Abstract
The invention relates to a coupling output structure of a terahertz quantum cascade laser, which comprises the terahertz quantum cascade laser, a first off-axis parabolic reflector and a second off-axis parabolic reflector, wherein the focus of the first off-axis parabolic reflector is positioned in the front end surface of the terahertz quantum cascade laser and is used for collecting and collimating laser emitted by the terahertz quantum cascade laser and forming a first quasi-parallel light beam; the second off-axis parabolic reflector is located in the rear end face of the terahertz quantum cascade laser and used for collecting and collimating laser light emitted by the terahertz quantum cascade laser and forming a second quasi-parallel light beam. The invention also relates to a packaging method of the coupling output structure of the terahertz quantum cascade laser. The invention can realize the high-efficiency coupling output of the laser with double end faces.
Description
Technical Field
The invention relates to the technical field of terahertz lasers, in particular to a coupling output structure of a terahertz quantum cascade laser and a packaging method thereof.
Background
Terahertz (THz) Quantum Cascade Laser (QCL) is a very important compact laser source in the THz frequency band, and has the characteristics of small volume, stable performance, high energy conversion efficiency, long service life and the like. Among THz QCLs of various shapes, ridge stripe devices are the most common one. Because the size of the laser ridge in the thickness direction is smaller than the laser wavelength, the laser emitted by the THz QCL end surface presents certain divergence, in order to improve the output beam of the laser, the ridge structure or the laser output end surface can be subjected to process improvement, and the quality of the output laser beam is improved by preparing a structural grating or an end surface microstructure, but the method increases the process preparation difficulty of the device, and meanwhile, the final output optical power of the device suffers certain loss due to the change of the ridge structure; another method is to add a micro optical structure such as a high-resistance silicon lens on the end face of the ridge stripe laser to improve the beam quality, but because the high-resistance silicon lens also has a certain absorption to the THz laser, there is a certain loss in the optical power finally output by the improved device compared with the optical power output by the improved front end face. Therefore, there is a need to find better methods of coupling out that reduce losses.
In addition, when the ridge stripe laser works, the front end face and the rear end face of the ridge stripe laser have symmetry and the same property, and the frequency and the power of output laser are basically consistent. However, in the practical application process, only one end face of the laser is usually coupled, and the adopted coupling output method needs to operate and move the position of the coupling optical element under vacuum, so that the implementation mode is complex, the low-temperature dewar air leakage condition is easy to occur, and the laser output by the other end face is wasted; although there is a method of increasing the total power of the light-emitting end face by evaporating the medium/metal high-reflection film on the other end face, due to the low quality of the preparation process of the high-reflection film and the reflection loss of the laser output end face, the improvement can only obtain the laser power of about 1.4 times of single-side output, and still 0.6 times of single-side output power is wasted. The structure of simultaneous coupling-out of two end faces of the laser is not reported at present. Therefore, in order to realize effective coupling of the output power of the other end surface, so that the total output power of the laser reaches 2 times of the single-surface output power, the problems of efficient coupling and simultaneous output of the laser light output by the two end surfaces of the ridge stripe laser are urgently needed to be solved.
Disclosure of Invention
The invention provides a coupling output structure of a terahertz quantum cascade laser and a packaging method thereof, which can realize high-efficiency coupling output of laser on double end faces.
The technical scheme adopted by the invention for solving the technical problems is as follows: the coupling output structure of the terahertz quantum cascade laser comprises the terahertz quantum cascade laser, a first off-axis parabolic reflector and a second off-axis parabolic reflector, wherein the focus of the first off-axis parabolic reflector is located in the front end face of the terahertz quantum cascade laser and is used for collecting and collimating laser light emitted by the terahertz quantum cascade laser and forming a first quasi-parallel light beam; the second off-axis parabolic reflector is located in the rear end face of the terahertz quantum cascade laser and used for collecting and collimating laser light emitted by the terahertz quantum cascade laser and forming a second quasi-parallel light beam.
The focus of the first off-axis parabolic reflector is coincided with the center of the front end face of the terahertz quantum cascade laser; the focus of the second off-axis parabolic reflector coincides with the center of the rear end face of the terahertz quantum cascade laser.
The terahertz quantum cascade laser is packaged on a heat sink, and the heat sink, the first off-axis parabolic reflector and the second off-axis parabolic reflector are mounted on a heat conducting sample frame.
The terahertz quantum cascade laser is of a single-sided metal waveguide structure or a semi-insulating surface plasma structure.
The working frequency range of the terahertz quantum cascade laser covers 1.2-5.2 THz.
The diameter focal length ratio of the first off-axis parabolic reflector and the diameter focal length ratio of the second off-axis parabolic reflector are both 0.5-1.
The reflecting angles of the first off-axis parabolic reflector and the second off-axis parabolic reflector are both 90 degrees, and the reflecting surfaces are both gold-plated reflecting surfaces.
The heat sink is made of gold-plated pure copper material.
The heat conduction sample rack is made of gold-plated pure copper material.
The technical scheme adopted by the invention for solving the technical problems is as follows: the packaging method of the coupling output structure of the terahertz quantum cascade laser comprises the following steps:
(1) packaging the terahertz quantum cascade laser on a heat sink;
(2) mounting a heat sink on a thermally conductive sample holder;
(3) determining the diameter, the focal point height and the focal length parameters of the first off-axis parabolic reflector and the second off-axis parabolic reflector, and respectively packaging the first off-axis parabolic reflector and the second off-axis parabolic reflector on a heat conduction sample rack by adopting a fixing material, so that the height of the center of the front end face of the terahertz quantum cascade laser is the same as the height of the focal point of the first off-axis parabolic reflector, and the height of the center of the rear end face of the terahertz quantum cascade laser is the same as the height of the focal point of the second off-axis parabolic reflector.
(4) Before the fixed material is solidified, aligning the center of the front end face and the center of the rear end face of the terahertz quantum cascade laser with the optical axis center line of the first off-axis parabolic reflector and the optical axis center line of the second off-axis parabolic reflector respectively by adopting a microscope marking alignment method, ensuring that the center of the front end face is coincided with the focus of the first off-axis parabolic reflector, the center of the rear end face is coincided with the focus of the second off-axis parabolic reflector, and keeping the alignment process until the fixed material is solidified and formed.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:
(1) the coupling output structure of the terahertz quantum cascade laser adopts the gold-plated reflecting surface, so that the terahertz quantum cascade laser has low reflection loss and high coupling efficiency;
(2) the coupling output structure of the terahertz quantum cascade laser adopts a double-reflector coupling structure, can simultaneously couple and output the output lasers at the front end surface and the rear end surface of the laser, and greatly improves the effective output power of the laser compared with the existing external coupling output structure;
(3) the coupling output structure of the terahertz quantum cascade laser can simultaneously output two beams of quasi-parallel terahertz laser with the same property, can simultaneously act on a target system without beam splitting, reduces optical elements of the system, improves the utilization efficiency of the laser, and is convenient for effectively comparing systems respectively acted by the two beams of laser.
(4) The coupling output structure of the terahertz quantum cascade laser has the advantages of compact structure, stability, reliability, no vacuum moving part for calibration, and great reduction of the risk of vacuum air leakage in the use process of the laser.
(5) In the packaging process of the coupling output structure of the terahertz quantum cascade laser, an auxiliary packaging method of microscope observation alignment is adopted, so that the packaging precision of the device is greatly improved, and a good technical means is provided for realizing quasi-parallel output of terahertz laser.
Drawings
Fig. 1 is a schematic structural diagram of a coupling-out structure of a terahertz quantum cascade laser of the present invention;
fig. 2 is a pulse peak output power curve of the terahertz quantum cascade laser effective at a temperature of 6K according to the preferred embodiment of the present invention, in which a solid line corresponds to the total output power of two end faces, and a dotted line corresponds to the output power of a front end face.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The embodiment of the invention relates to a coupling output structure of a terahertz quantum cascade laser, which can realize high-efficiency coupling output of laser on two end faces.
Fig. 1 shows an implementation apparatus of a coupling-out structure of a terahertz quantum cascade laser according to a preferred embodiment of the present invention, including: terahertz quantum cascade laser 1, heat sink 2, first off-axis parabolic reflector 3, second off-axis parabolic reflector 4 and heat conducting sample holder 5
As shown in fig. 1, a focus of the first off-axis parabolic mirror 3 coincides with a center of a front end surface 11 of the terahertz quantum cascade laser 1, a first quasi-parallel light beam 6 is formed after laser coupling is output to the front end surface 11, a focus of the second off-axis parabolic mirror 4 coincides with a center of a rear end surface 12 of the terahertz quantum cascade laser 1, and a second quasi-parallel light beam 7 is formed after laser coupling is output to the rear end surface 12.
In the present embodiment, the ratio of the focal length of the diameter of the first off-axis parabolic mirror 3 to the focal length of the diameter of the second off-axis parabolic mirror 4 is preferably 0.5 to 1, and the ratio of the focal length of the diameter is preferably 0.52.
Further, the reflecting surfaces of the first off-axis parabolic reflector 3 and the second off-axis parabolic reflector 4 are 90-degree off-axis gold-plated reflecting surfaces.
In the present embodiment, the terahertz quantum cascade laser 1 is a single-sided metal waveguide structure or a semi-insulating surface plasmon structure.
Further, the length of the terahertz quantum cascade laser 1 is 4mm, the width is 300 μm, and the thickness is 200 μm.
Further, the lasing frequency of the terahertz quantum cascade laser 1 is 4.3 THz.
In a preferred embodiment, as shown in fig. 2, the total pulse peak output power of the two end faces of the terahertz quantum cascade laser 1 is 1.05mW, the pulse peak output power of the front end face is 0.53mW, the power meter used for measuring the power is TK 100, the diameter of the sensitive area of the power meter is 30mm, and the laser driving current density corresponding to the pulse peak output power is 1230A-cm-2Thus, the total output power of the two end faces is close to 2 times of the single-face output power.
In the present embodiment, the heat sink 2 is a surface gold-plated pure copper material, and has dimensions of 4mm in width, 26mm in length, and 4mm in thickness. The heat conducting sample holder 5 is made of gold-plated pure copper material.
Another embodiment of the present specification further provides a packaging method of a coupling-out structure of a terahertz quantum cascade laser, which is used for manufacturing the above-mentioned laser coupling-out structure.
The method specifically comprises the following steps:
s01: the terahertz quantum cascade laser 1 is packaged at the right center of the heat sink 2 through a high-purity indium material with the purity of 99.99%, and the front end face 11 and the rear end face 12 of the packaged terahertz quantum cascade laser are aligned with the length edge of the heat sink 2;
s02: installing the heat sink 2 on the heat conduction sample frame 5 according to the designed position, wherein the central point of the heat sink 2 is positioned in the right center of the heat conduction sample frame 5 after installation;
s03: designing the diameter of a first off-axis parabolic reflector 3 and a second off-axis parabolic reflector 4 to be 10mm, the focal length to be 5.2mm, and the height of the focal point to the bottom surface of a reflector body to be 4mm, respectively packaging the first off-axis parabolic reflector 3 and the second off-axis parabolic reflector 4 on a heat conduction sample rack 5 by adopting a low-temperature adhesive, wherein the thickness of the adhered low-temperature adhesive is 0.1mm, and at the moment, the focal point height of the first off-axis parabolic reflector 3 is 4.1mm, so that the height of the center of a front end surface 11 of a terahertz quantum cascade laser 1 is half of the thickness of a device and is 100 mu m, and the thickness of a heat sink is 4.1mm, and the height of the focal point of the first off-axis parabolic reflector 3 is the same as that of the center of a rear end surface 12 of the terahertz quantum cascade laser 1 is the same as that of the focal point of the second off-axis parabolic reflector;
s05: before the low-temperature adhesive material is solidified, the center of the front end surface 11 and the center of the rear end surface 12 of the terahertz quantum cascade laser 1 are respectively aligned with the optical axis center line of the first off-axis parabolic reflector 3 and the optical axis center line of the second off-axis parabolic reflector 4 by adopting a microscope marking alignment method, so that the center of the front end surface 11 is ensured to be coincided with the focus of the first off-axis parabolic reflector 3, the center of the rear end surface 12 is coincided with the focus of the second off-axis parabolic reflector 4, the alignment process is kept until the low-temperature adhesive material is solidified and formed, and the keeping time is 30 minutes.
The invention provides a coupling output structure of a terahertz quantum cascade laser and a packaging method thereof, wherein a gold-plated reflecting surface is adopted, so that the terahertz laser has low reflection loss and high coupling efficiency; the double-reflector coupling structure is adopted, the output lasers of the front end surface and the rear end surface of the laser can be coupled and output at the same time, and compared with the existing external coupling output structure, the effective output power of the laser is greatly improved; the structure can simultaneously output two beams of quasi-parallel terahertz lasers with the same property, can simultaneously act on a target system without beam splitting, reduces optical elements of the system, improves the utilization efficiency of the lasers, and is convenient for effective comparison of systems respectively acted by the two beams of lasers; the structure has the advantages of compact structure, stability and reliability, no vacuum moving part for calibration, and greatly reduced risk of vacuum air leakage in the use process of the laser; in the packaging process of the structure, an auxiliary packaging method of microscope observation alignment is adopted, the packaging precision of the device is greatly improved, and a good technical means is provided for realizing quasi-parallel output of terahertz laser.
Claims (10)
1. A coupling output structure of a terahertz quantum cascade laser comprises a terahertz quantum cascade laser (1), a first off-axis parabolic reflector (3) and a second off-axis parabolic reflector (4), and is characterized in that the focus of the first off-axis parabolic reflector (3) is located in the front end face (11) of the terahertz quantum cascade laser (1) and used for collecting and collimating laser light emitted by the terahertz quantum cascade laser (1) and forming a first quasi-parallel light beam (6); the second off-axis parabolic reflector (4) is located in the rear end face (12) of the terahertz quantum cascade laser and used for collecting and collimating laser light emitted by the terahertz quantum cascade laser (1) and forming a second quasi-parallel light beam (7).
2. The coupling-out structure of the terahertz quantum cascade laser according to claim 1, wherein the focus of the first off-axis parabolic mirror (3) coincides with the center of the front end face (11) of the terahertz quantum cascade laser (1); the focus of the second off-axis parabolic reflector (4) is coincided with the center of the rear end face (12) of the terahertz quantum cascade laser (1).
3. The coupling-out structure of the terahertz quantum cascade laser according to claim 1, wherein the terahertz quantum cascade laser (1) is packaged on a heat sink (2), and the heat sink (2), the first off-axis parabolic mirror (3) and the second off-axis parabolic mirror (4) are mounted on a heat-conducting sample holder (5).
4. The coupling-out structure of the terahertz quantum cascade laser according to claim 1, wherein the terahertz quantum cascade laser (1) is a single-sided metal waveguide structure or a semi-insulating surface plasmon structure.
5. The coupling-out structure of the terahertz quantum cascade laser device as claimed in claim 1, wherein the working frequency range of the terahertz quantum cascade laser device (1) covers 1.2-5.2 THz.
6. The coupling-out structure of the terahertz quantum cascade laser as claimed in claim 1, wherein the diameter focal length ratio of the first off-axis parabolic mirror (3) and the diameter focal length ratio of the second off-axis parabolic mirror (4) are both between 0.5 and 1.
7. The coupling-out structure of the terahertz quantum cascade laser according to claim 1, wherein the reflection angles of the first off-axis parabolic mirror (3) and the second off-axis parabolic mirror (4) are both 90 degrees, and the reflection surfaces are both gold-plated reflection surfaces.
8. The coupling-out structure of the terahertz quantum cascade laser as claimed in claim 2, wherein the heat sink (2) is a surface gold-plated pure copper material.
9. The coupling-out structure of the terahertz quantum cascade laser as claimed in claim 2, wherein the heat conducting sample holder (5) is a pure copper material with gold-plated surface.
10. A packaging method of a coupling-out structure of a terahertz quantum cascade laser as claimed in any one of claims 1 to 9, comprising the following steps:
(1) the terahertz quantum cascade laser (1) is packaged on a heat sink (2);
(2) mounting a heat sink (2) on a heat-conducting sample holder (5);
(3) determining the diameter, the focal point height and the focal length parameters of the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4), respectively packaging the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4) on a heat conduction sample rack (5) by adopting a fixing material, so that the height of the center of the front end surface (11) of the terahertz quantum cascade laser (1) is the same as the height of the focal point of the first off-axis parabolic reflector (3), and the height of the center of the rear end surface (12) of the terahertz quantum cascade laser (1) is the same as the height of the focal point of the second off-axis parabolic reflector (4);
(4) before the fixed material is solidified, the center of a front end face (11) and the center of a rear end face (12) of the terahertz quantum cascade laser (1) are aligned with the optical axis center line of the first off-axis parabolic reflector (3) and the optical axis center line of the second off-axis parabolic reflector (4) respectively by adopting a microscope reticle alignment method, so that the center of the front end face (11) is ensured to be coincided with the focus of the first off-axis parabolic reflector (3), the center of the rear end face (12) is coincided with the focus of the second off-axis parabolic reflector (4), and the alignment process is kept until the fixed material is solidified and formed.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113381289A (en) * | 2021-06-10 | 2021-09-10 | 中国科学院半导体研究所 | Optical feedback structure and packaging method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113381289A (en) * | 2021-06-10 | 2021-09-10 | 中国科学院半导体研究所 | Optical feedback structure and packaging method thereof |
| CN113381289B (en) * | 2021-06-10 | 2022-05-17 | 中国科学院半导体研究所 | Optical feedback structure and packaging method thereof |
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