CN111952837A - A coupling output structure of a terahertz quantum cascade laser and its packaging method - Google Patents

Abstract

The invention relates to a coupling output structure of a terahertz quantum cascaded laser, comprising a terahertz quantum cascaded laser, a first off-axis parabolic mirror, and a second off-axis parabolic mirror. The focal point is located in the front end surface of the terahertz quantum cascade laser to collect and collimate the laser light emitted by the terahertz quantum cascade laser, and form a first quasi-parallel beam; the second off-axis parabolic mirror It is located in the rear end surface of the terahertz quantum cascade laser, and is used for collecting and collimating the laser light emitted by the terahertz quantum cascade laser, and forming a second quasi-parallel beam. The invention also relates to a packaging method of the coupling-out structure of the terahertz quantum cascade laser. The invention can realize the high-efficiency coupling output of the laser with double end faces.

Description

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

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 technique

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 QCLs, the ridge-stripe device is the most common one. Since the size of the laser ridge in the thickness direction is smaller than the laser wavelength, the laser emitted from the end face of the THz QCL exhibits a certain divergence. Structural gratings or end-face microstructures are prepared to improve the quality of the output laser beam. However, this method increases the difficulty of device fabrication, and at the same time, due to the change of the ridge structure, the final output optical power of the device suffers a certain loss; another One way is to improve the beam quality by adding micro-optical structures such as high-resistance silicon lenses to the end face of the ridge-stripe laser. There is also a certain loss in the final output optical power of the device after improvement. Therefore, it is necessary to find a better coupling-out method to reduce the loss.

In addition, when the ridge bar laser works, 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 the actual application process, only one end face of the laser is usually coupled, and the coupling-out method used requires the position of the coupling optics to be moved under vacuum. 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 by evaporating a medium/metal high-reflection film, due to the low quality of the preparation process of the high-reflection film and the laser There is reflection loss on the output end face, etc. The above improvement usually only obtains 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 in which the two end faces of the laser are coupled out at the same time has not yet been reported. Therefore, in order to realize the effective coupling of the output power of the other end face and make the total output power of the laser reach twice the output power of the single face, it is urgent to solve the problem of efficient coupling and simultaneous output of the two end faces of the ridge bar laser.

SUMMARY OF THE 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 double-end surface lasers.

The technical solution adopted by the present invention to solve the technical problem is to provide a coupling output structure of a terahertz quantum cascade laser, including a terahertz quantum cascade laser, a first off-axis parabolic mirror, and a second off-axis parabolic mirror , the focus of the first off-axis parabolic mirror is located in the front end surface of the terahertz quantum cascade laser to collect and collimate the laser light emitted by the terahertz quantum cascade laser, and form a first quasi-parallel a light beam; the second off-axis parabolic mirror is located in the rear end face of the terahertz quantum cascade laser to collect and collimate the laser light emitted by the terahertz quantum cascade laser, and form a second quasi-parallel beam .

The focus of the first off-axis parabolic mirror coincides with the center of the front face of the terahertz quantum cascade laser; the focus of the second off-axis parabolic mirror is coincident with the rear face of the terahertz quantum cascade laser the center coincides.

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

The terahertz quantum cascade laser is a single-sided metal waveguide structure or a semi-insulating surface plasmon structure.

The operating frequency range of the terahertz quantum cascade laser covers 1.2-5.2 THz.

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

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

The heat sink is made of gold-plated pure copper material.

The thermally conductive sample holder is made of gold-plated pure copper material.

The technical solution adopted by the present invention to solve the technical problem is to provide a packaging method for the coupling-out structure of the terahertz quantum cascade laser, which includes the following steps:

(1) encapsulating the terahertz quantum cascade laser on a heat sink;

(2) Install the heat sink on the thermally conductive sample holder;

(3) Determine the diameter, focus height and focal length parameters of the first off-axis parabolic mirror and the second off-axis parabolic mirror, and use a fixed material to separate the first off-axis parabolic mirror and the second off-axis parabolic mirror respectively. It is packaged in a thermally conductive sample holder, so that the height of the center of the front face of the terahertz quantum cascade laser is the same as the height of the focus of the first off-axis parabolic mirror, and the height of the center of the rear face of the terahertz quantum cascade laser is the same as the height of the second off-axis The height of the focal point of the parabolic mirror is the same.

(4) Before the solidification of the fixed material, the center of the front end surface and the center of the rear end surface of the terahertz quantum cascade laser are respectively aligned with the center line of the optical axis of the first off-axis parabolic mirror and The center lines of the optical axis of the second off-axis parabolic mirror are aligned to ensure that the center of the front surface coincides with the focus of the first off-axis parabolic mirror, and the center of the rear surface coincides with the focus of the second off-axis parabolic mirror. The quasi-process is maintained until the fixing material solidifies and takes shape.

beneficial effect

Due to adopting the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art:

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

(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 end faces of the laser. Compared with the existing external coupling output structure, it is greatly improved. Improve the effective output power of the laser;

(3) The coupling output structure of the terahertz quantum cascade laser of the present invention can output two quasi-parallel terahertz laser beams with the same properties at the same time, and can act on the target system at the same time without beam splitting, reducing the optical system of the system. It improves the efficiency of laser utilization and facilitates the effective comparison of the systems in which the two laser beams act respectively.

(4) The coupling output structure of the terahertz quantum cascade laser of the present invention has a compact structure, is 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.

(5) In the packaging process of the coupling-out structure of the terahertz quantum cascade laser of the present invention, the auxiliary packaging method of microscope observation and alignment is adopted, which greatly improves the precision of the device packaging and provides the quasi-parallel output of the terahertz laser. good technical means.

Description of drawings

Fig. 1 is the structural representation of the coupling-out structure of the terahertz quantum cascade laser of the present invention;

2 is the effective pulse peak output power curve of the terahertz quantum cascade laser according to the preferred embodiment of the present invention at a temperature of 6K, wherein the solid line corresponds to the total output power of the two end faces, and the dotted line corresponds to the output power of the front end face. .

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not 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 also fall within the scope defined by the appended claims of the present application.

The embodiments of the present invention relate to a coupling-out structure of a terahertz quantum cascade laser, which can realize high-efficiency coupling-out of the laser with double-end faces.

Fig. 1 shows an implementation device of a terahertz quantum cascade laser coupling-out structure according to a preferred embodiment of the present invention, including: a terahertz quantum cascade laser 1, a heat sink 2, a first off-axis parabolic mirror 3, Second off-axis parabolic mirror 4 and thermally conductive sample holder 5

As shown in FIG. 1 , the focus of the first off-axis parabolic mirror 3 is coincident with the center of the front end surface 11 of the terahertz quantum cascade laser 1 , and the output laser is coupled to the front end surface 11 to form a first quasi-parallel beam 6 . The focus of the second off-axis parabolic mirror 4 is coincident with the center of the rear surface 12 of the terahertz quantum cascade laser 1 , and the output laser is coupled to the rear surface 12 to form a second quasi-parallel beam 7 .

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

Further, the reflective surfaces of the first off-axis parabolic mirror 3 and the second off-axis parabolic mirror 4 are both 90-degree off-axis gold-plated reflective surfaces.

In this 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 4 mm, the width is 300 μm, and the thickness is 200 μm.

Further, the excitation frequency of the terahertz quantum cascade laser 1 is 4.3 THz.

As 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, and the power used for measuring the power is Calculated as TK 100, the diameter of the sensitive surface area of the power meter is 30mm, and the laser driving current density corresponding to the pulse peak output power is 1230A·cm ^-2 , which indicates that the total output power of the two end faces is nearly twice that of the single-sided output power.

In this embodiment, the heat sink 2 is made of gold-plated pure copper material, and its dimensions are 4 mm in width, 26 mm in length, and 4 mm in thickness. The thermally conductive sample holder 5 is made of gold-plated pure copper material.

Another embodiment of the present specification also provides a packaging method for the coupling-out structure of a terahertz quantum cascade laser, which is used to fabricate the above-mentioned laser coupling-out.

Specifically include the following steps:

S01: The terahertz quantum cascade laser 1 is encapsulated in the center of the heat sink 2 by a high-purity indium material with a purity of 99.99%, and the front and rear surfaces 11 and 12 of the terahertz quantum cascade laser 1 are aligned with the length of the heat sink 2 after encapsulation;

S02: Install the heat sink 2 on the thermally conductive sample holder 5 according to the designed position, and after installation, the center point of the heat sink 2 is located in the center of the thermally conductive sample holder 5;

S03: Design the diameter of the first off-axis parabolic mirror 3 and the second off-axis parabolic mirror 4 to be 10 mm, the focal length to be 5.2 mm, and the height of the focal distance from the bottom surface of the mirror body to be 4 mm, and the first off-axis paraboloid is reflected by using a low-temperature glue material The mirror 3 and the second off-axis parabolic mirror 4 are respectively packaged on the thermally conductive sample holder 5, wherein the thickness of the low-temperature adhesive after bonding is 0.1 mm, and the focal height of the first off-axis parabolic mirror 3 is 4.1 mm at this time, so that The height of the center of the front face 11 of the terahertz quantum cascade laser 1 is half the thickness of the device, which is 100 μm, plus the thickness of the heat sink is 4 mm, which is 4.1 mm, and the height of the focal point of the first off-axis parabolic mirror 3 is the same. The height of the center of the rear face 12 of the Hertz quantum cascade laser 1 is the same as the height of the focal point of the second off-axis parabolic mirror 4, which is also 4.1 mm;

S05: Before the low-temperature glue material solidifies, use the method of microscope reticle alignment to align the center of the front end surface 11 and the center of the rear end surface 12 of the terahertz quantum cascade laser 1 with the center line of the optical axis of the first off-axis parabolic mirror 3 respectively. Align with the center line of the optical axis of the second off-axis parabolic mirror 4 to ensure that the center of the front surface 11 coincides with the focus of the first off-axis parabolic mirror 3, and the center of the rear surface 12 coincides with the focus of the second off-axis parabolic mirror 4, and The above alignment process is maintained until the low temperature adhesive material is solidified and formed, and the holding time is 30 minutes.

The invention provides a coupling output structure of a terahertz quantum cascade laser and a packaging method thereof, which adopts a gold-plated reflective surface, which has low reflection loss to the terahertz laser and high coupling efficiency; , The output lasers of the latter two end faces are simultaneously coupled and output, compared with the existing external coupling output structure, the effective output power of the laser is greatly improved; this structure can output two quasi-parallel terahertz laser beams with the same properties at the same time, no need By splitting the beam, it can act on the target system at the same time, reducing the optical components of the system, improving the efficiency of laser utilization, and at the same time facilitating the effective comparison of the systems in which the two laser beams act respectively; the structure is compact, stable and reliable, and has no vacuum. The moving parts are calibrated, which greatly reduces the risk of vacuum leakage during the use of the laser; during the packaging process of the structure, the auxiliary packaging method of microscope observation and alignment is adopted, which greatly improves the precision of device packaging. Parallel output provides a good technical means.

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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