A coupling output structure of a terahertz quantum cascade laser and a packaging method thereof

Abstract

The present invention relates to a coupled output structure of a terahertz quantum cascade laser, comprising a 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, for collecting and collimating the 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, for collecting and collimating the laser light emitted by the terahertz quantum cascade laser, and forming a second quasi-parallel light beam. The present invention also relates to a packaging method for a coupled output structure of a terahertz quantum cascade laser. The present invention can achieve efficient coupled output of laser light at both ends.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz lasers, and in particular to a coupled output structure of a terahertz quantum cascade laser and a packaging method thereof. Background Art

[0002] Terahertz (THz) quantum cascade laser (QCL) is a very important compact laser source in the THz frequency band. It has the characteristics of small size, stable performance, high energy conversion efficiency and long service life. Among the various shapes of THz QCL, ridge strip device is the most common one. Since the size of the laser ridge strip in the thickness direction is smaller than the laser wavelength, the laser emitted from the end face of the THz QCL shows a certain divergence. In order to improve the output beam of this laser, the ridge strip structure or the laser output end face can be improved by making a structured grating or end face microstructure to improve the quality of its output laser beam. However, this method increases the difficulty of device process preparation. At the same time, due to the change of the ridge strip structure, the final output optical power of the device suffers a certain loss; another way is to improve the beam quality by adding a micro optical structure such as a high-resistance silicon lens to the end face of the ridge strip laser, but since the high-resistance silicon lens also has a certain absorption of the THz laser, compared with improving the optical power output from the front face, the final output optical power of the device after improvement also has a certain loss. Therefore, it is necessary to find a better coupling output method to reduce the loss.

[0003] In addition, when the ridge laser is working, its front and rear end faces have symmetry and the same properties, and the frequency and power of the output laser are basically the same. However, in actual application, only one end face of the laser is usually coupled, and the coupling output method used requires the position of the coupling optical component to be moved under vacuum. The implementation method is relatively complicated and prone to low-temperature Dewar leakage. At this time, the laser output from the other end face is wasted; although there is also a way to increase the total power of the light-emitting end face by evaporating the other end face with a medium / metal high-reflection film, 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 above improvement can usually only obtain about 1.4 times the laser power of the single-sided output, and 0.6 times the single-sided output power is still wasted. The structure of coupling the output of both end faces of the laser at the same time has not been reported yet. Therefore, in order to achieve effective coupling of the output power of the other end face so that the total output power of the laser reaches twice the single-sided output power, it is urgent to solve the problem of efficient coupling and simultaneous output of the laser output from the two end faces of the ridge laser. Summary of the invention

[0004] The present invention provides a coupled output structure of a terahertz quantum cascade laser and a packaging method thereof, which can realize efficient coupled output of lasers at both ends.

[0005] The technical solution adopted by the present invention to solve its technical problem is: providing a coupled output structure of a terahertz quantum cascade laser, comprising a 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, so as to collect and collimate the laser light emitted by the terahertz quantum cascade laser, and form 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, so as to collect and collimate the laser light emitted by the terahertz quantum cascade laser, and form a second quasi-parallel light beam.

[0006] The focus of the first off-axis parabolic reflector coincides 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.

[0007] The terahertz quantum cascade laser is packaged on a heat sink, and the heat sink, a first off-axis parabolic reflector and a second off-axis parabolic reflector are mounted on a thermally conductive sample holder.

[0008] The terahertz quantum cascade laser is a single-sided metal waveguide structure or a semi-insulating surface plasma structure.

[0009] The operating frequency range of the terahertz quantum cascade laser covers 1.2 to 5.2 THz.

[0010] The diameter-to-focal length ratio of the first off-axis parabolic reflector and the diameter-to-focal length ratio of the second off-axis parabolic reflector are both between 0.5 and 1.

[0011] The reflection angles of the first off-axis parabolic reflector and the second off-axis parabolic reflector are both 90 degrees, and the reflection surfaces are both gold-plated reflection surfaces.

[0012] The heat sink is made of pure copper material with gold-plated surface.

[0013] The thermally conductive sample holder is made of pure copper material with gold-plated surface.

[0014] The technical solution adopted by the present invention to solve the technical problem is: to provide a packaging method for a coupled output structure of a terahertz quantum cascade laser, comprising the following steps:

[0015] (1) packaging the terahertz quantum cascade laser on a heat sink;

[0016] (2) Installing the heat sink on the thermally conductive sample holder;

[0017] (3) Determine the diameter, focal height and focal length parameters of the first off-axis parabolic reflector and the second off-axis parabolic reflector, and respectively package the first off-axis parabolic reflector and the second off-axis parabolic reflector on a thermally conductive sample holder using 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.

[0018] (4) Before the fixed material solidifies, the center of the front face and the center of the rear face of the terahertz quantum cascade laser are aligned with the center line of the optical axis of the first off-axis parabolic reflector and the center of the rear face of the terahertz quantum cascade laser respectively using a microscope marking alignment method, ensuring that the center of the front face coincides with the focus of the first off-axis parabolic reflector and the center of the rear face coincides with the focus of the second off-axis parabolic reflector, and the above alignment process is maintained until the fixed material solidifies.

[0019] Beneficial Effects

[0020] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0021] (1) The coupling output structure of the terahertz quantum cascade laser of the present invention adopts a gold-plated reflective surface, which has low reflection loss of terahertz laser and high coupling efficiency;

[0022] (2) The coupling output structure of the terahertz quantum cascade laser of the present invention adopts a double-mirror coupling structure, which can simultaneously couple the output lasers of the front and rear ends of the laser, greatly improving the effective output power of the laser compared with the existing external coupling output structure;

[0023] (3) The coupled output structure of the terahertz quantum cascade laser of the present invention can simultaneously output two quasi-parallel terahertz laser beams with the same properties, and can act on the target system at the same time without beam splitting, thereby reducing the optical components of the system, improving the laser utilization efficiency, and facilitating effective comparison of systems where two laser beams act separately.

[0024] (4) The coupled output structure of the terahertz quantum cascade laser of the present invention is compact, stable and reliable, and has no vacuum moving parts for calibration, which greatly reduces the risk of vacuum leakage during the use of the laser.

[0025] (5) During the packaging process of the coupled output structure of the terahertz quantum cascade laser of the present invention, an auxiliary packaging method of microscope observation alignment is adopted, which greatly improves the accuracy of device packaging and provides a good technical means for realizing quasi-parallel output of terahertz laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the coupled output structure of the terahertz quantum cascade laser of the present invention;

[0027] Figure 2 1 is an effective pulse peak output power curve of the terahertz quantum cascade laser at 6K temperature according to a preferred embodiment of the present invention, wherein the solid line corresponds to the total output power of the two end faces, and the dot-dashed line corresponds to the output power of the front end face. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] The embodiment of the present invention relates to a coupling output structure of a terahertz quantum cascade laser, which can realize efficient coupling output of lasers at both ends.

[0030] Figure 1 The device for realizing the coupled output structure of a terahertz quantum cascade laser according to a preferred embodiment of the present invention is shown, comprising: a terahertz quantum cascade laser 1, a heat sink 2, a first off-axis parabolic reflector 3, a second off-axis parabolic reflector 4 and a thermally conductive sample holder 5.

[0031] like Figure 1 As shown, the focus of the first off-axis parabolic reflector 3 coincides with the center of the front end face 11 of the terahertz quantum cascade laser 1, and the front end face 11 is output laser coupled to form a first quasi-parallel light beam 6, and the focus of the second off-axis parabolic reflector 4 coincides with the center of the rear end face 12 of the terahertz quantum cascade laser 1, and the rear end face 12 is output laser coupled to form a second quasi-parallel light beam 7.

[0032] In this embodiment, the diameter-to-focal length ratio of the first off-axis parabolic reflector 3 and the diameter-to-focal length ratio of the second off-axis parabolic reflector 4 are both between 0.5 and 1. Preferably, the diameter-to-focal length ratio is set to 0.52.

[0033] Furthermore, the reflecting surfaces of the first off-axis parabolic reflector 3 and the second off-axis parabolic reflector 4 are both 90-degree off-axis gold-plated reflecting surfaces.

[0034] In this embodiment, the terahertz quantum cascade laser 1 is a single-sided metal waveguide structure or a semi-insulating surface plasma structure.

[0035] Furthermore, the terahertz quantum cascade laser 1 has a length of 4 mm, a width of 300 μm, and a thickness of 200 μm.

[0036] Furthermore, the lasing frequency of the terahertz quantum cascade laser 1 is 4.3 THz.

[0037] As a preferred embodiment, Figure 2 As shown, the total pulse peak output power of the two end faces of the terahertz quantum cascade laser 1 is 1.05 mW, the pulse peak output power of the front end face is 0.53 mW, the power meter used to measure the power is TK 100, the diameter of the sensitive surface area of ​​the power meter is 30 mm, and the laser driving current density corresponding to the pulse peak output power is 1230 A cm -2 , which means that the total output power of the two end faces is nearly twice the output power of a single side.

[0038] In this embodiment, the heat sink 2 is made of pure copper with gold plating on the surface, and its dimensions are 4 mm in width, 26 mm in length, and 4 mm in thickness. The thermal conductive sample holder 5 is made of pure copper with gold plating on the surface.

[0039] Another embodiment of the present specification also provides a packaging method for a terahertz quantum cascade laser coupling output structure, which is used to produce the laser coupling output described above.

[0040] Specifically, the following steps are included:

[0041] S01: encapsulating the terahertz quantum cascade laser 1 in the center of the heat sink 2 using a high-purity indium material with a purity of 99.99%. After encapsulation, the front end face 11 and the rear end face 12 of the terahertz quantum cascade laser 1 are aligned with the length side of the heat sink 2;

[0042] S02: installing the heat sink 2 on the thermal conductive sample holder 5 according to the designed position. After installation, the center point of the heat sink 2 is located at the exact center of the thermal conductive sample holder 5;

[0043] S03: The diameter of the first off-axis parabolic reflector 3 and the second off-axis parabolic reflector 4 is designed to be 10 mm, the focal length is 5.2 mm, and the height of the focal point from the bottom of the mirror body is 4 mm. The first off-axis parabolic reflector 3 and the second off-axis parabolic reflector 4 are respectively encapsulated on the thermal conductive sample holder 5 using a low-temperature adhesive material, wherein the thickness of the low-temperature adhesive after bonding is 0.1 mm. At this time, the focal height of the first off-axis parabolic reflector 3 is 4.1 mm, so that the height of the center of the front end face 11 of the terahertz quantum cascade laser 1 is half of the device thickness, which is 100 μm, plus the thickness of the heat sink 4 mm, which is 4.1 mm. The height of the focus of the first off-axis parabolic reflector 3 is the same. Similarly, the height of the center of the rear end face 12 of the terahertz quantum cascade laser 1 is the same as the height of the focus of the second off-axis parabolic reflector 4, which is also 4.1 mm.

[0044] S05: Before the low-temperature glue material solidifies, the center of the front end face 11 and the center of the 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 using the microscope marking alignment method, ensuring that the center of the front end face 11 coincides with the focus of the first off-axis parabolic reflector 3, and the center of the rear end face 12 coincides with the focus of the second off-axis parabolic reflector 4, and the above alignment process is maintained until the low-temperature glue material solidifies and takes shape, and the maintenance time is 30 minutes.

[0045] The invention proposes a coupled output structure of a terahertz quantum cascade laser and a packaging method thereof. A gold-plated reflective surface is adopted, which has low reflection loss for terahertz laser and high coupling efficiency. A double-reflector coupling structure is adopted, so that the output lasers of the front and rear end faces of the laser can be coupled and output simultaneously, and compared with the existing external coupled output structure, the effective output power of the laser is greatly improved. The structure can simultaneously output two quasi-parallel terahertz laser beams with the same properties, and can act on a target system simultaneously without beam splitting, thereby reducing the optical components of the system, improving the laser utilization efficiency, and facilitating effective comparison of systems in which the two laser beams act separately. The structure has the advantages of compact structure, stability and reliability, and no vacuum moving parts for calibration, which greatly reduces the risk of vacuum leakage during the use of the laser. In the packaging process of the structure, an auxiliary packaging method of microscope observation and alignment is adopted, which greatly improves the accuracy of device packaging and provides a good technical means for realizing the quasi-parallel output of terahertz lasers.

Claims

1. A coupled output structure of a terahertz quantum cascade laser, comprising a terahertz quantum cascade laser (1), a first off-axis parabolic reflector (3), and a second off-axis parabolic reflector (4), 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 is used to collect and collimate the laser light emitted by the terahertz quantum cascade laser (1), and form 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 is used to collect and collimate the laser light emitted by the terahertz quantum cascade laser (1), and form a second quasi-parallel light beam (7); the focus of the first off-axis parabolic reflector (3) coincides with the center of the front end face (11) of the terahertz quantum cascade laser (1); The focal points of the two off-axis parabolic reflectors (4) coincide with the center of the rear end face (12) of the terahertz quantum cascade laser (1); the terahertz quantum cascade laser (1) is packaged on a heat sink (2); the heat sink (2), the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4) are mounted on a heat-conducting sample holder (5); the diameter focal length ratio of the first off-axis parabolic reflector (3) and the diameter focal length ratio of the second off-axis parabolic reflector (4) are both between 0.5 and 1; the reflection angles of the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4) are both 90 degrees, and the reflection surfaces are both gold-plated reflection surfaces.

2. The coupling output structure of the terahertz quantum cascade laser according to claim 1, characterized in that: The terahertz quantum cascade laser (1) is a single-sided metal waveguide structure or a semi-insulating surface plasma structure.

3. The coupling output structure of the terahertz quantum cascade laser according to claim 1, characterized in that: The operating frequency range of the terahertz quantum cascade laser (1) covers 1.2 to 5.2 THz.

4. The coupling output structure of the terahertz quantum cascade laser according to claim 1, characterized in that: The heat sink (2) is made of pure copper material with a gold-plated surface.

5. The coupling output structure of the terahertz quantum cascade laser according to claim 1, characterized in that: The thermally conductive sample holder (5) is made of pure copper material with a gold-plated surface.

6. A packaging method for the coupled output structure of a terahertz quantum cascade laser as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) packaging the terahertz quantum cascade laser (1) on a heat sink (2); (2) installing the heat sink (2) on the thermally conductive sample holder (5); (3) determining the diameter, focal height and focal length parameters of the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4), and respectively encapsulating the first off-axis parabolic reflector (3) and the second off-axis parabolic reflector (4) on a heat-conducting sample holder (5) using a fixing material, so that the height of the center of the front end face (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 face (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 solidifies, the center of the front face (11) and the center of the rear 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 using a microscope marking alignment method, ensuring that the center of the front face (11) coincides with the focus of the first off-axis parabolic reflector (3), and the center of the rear face (12) coincides with the focus of the second off-axis parabolic reflector (4), and the above alignment process is maintained until the fixed material solidifies.

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