A high-power external cavity tunable quantum cascade laser output module

Abstract

The application provides a high-power external cavity tunable quantum cascade laser output module, which comprises a first lens, a first half-wave plate and a first mid-infrared grating polarizer arranged in sequence along the light path of a first laser; a second lens, a second half-wave plate, a second mid-infrared grating polarizer and a third half-wave plate arranged in sequence along the light path of a second laser; the emergent light of the first mid-infrared grating polarizer and the third half-wave plate is converged on different surfaces of a third mid-infrared grating polarizer, a first blazed grating is arranged on the reflection light path of the first mid-infrared grating polarizer, and a second blazed grating is arranged on the reflection light path of the second mid-infrared grating polarizer. The application can effectively solve the problems of wavelength locking and low polarization beam combining efficiency caused by the insufficient polarization state of the quantum cascade laser, and can realize narrow linewidth output and wavelength tuning of the quantum cascade laser, and even high-power dual-wavelength tunable output can be realized through the polarization beam combining structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor laser, in particular to a high-power external cavity tunable quantum cascade laser output module. BACKGROUND

[0002] Quantum cascade laser has been a focus of researchers since it was developed by Faist et al. in Bell Labs. The reason is that, compared with ordinary semiconductor lasers, it relies on a light emission process independent of the semiconductor band gap to operate, and can achieve laser output in the mid-infrared to terahertz band. In particular, it covers two important atmospheric windows of 3-5 μm and 8-12 μm, so it has great application value in free space communication, trace gas detection, etc. However, the traditional quantum cascade laser is mostly multi-longitudinal mode output and has low power, which is difficult to meet the needs of practical applications, so new requirements are put forward for the power, linewidth and tuning range of quantum cascade lasers.

[0003] There are three ways to achieve wavelength tuning: DBR grating, DFB grating and external cavity tuning. Compared with the above two methods, external cavity feedback quantum cascade laser does not require high design requirements for the light source itself, and can achieve single-longitudinal-mode, wide-tuning laser output, so it can meet the above requirements. The typical external cavity feedback quantum cascade laser can be divided into Littrow (as shown in Figure 5 Compared with the Littrow structure, the Littman structure has an additional mirror. Although a narrower linewidth can be obtained, the loss is increased.

[0004] However, the power of quantum cascade laser is low, and the degree of polarization is less than 100% (as shown in Figure 4 The output beam is not completely polarized light, and depolarization occurs under high current, which does not match the polarization characteristics of the blazed grating), which is not conducive to subsequent power scaling and limits the further application of this technology.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a high-power external cavity tunable quantum cascade laser output module, which can effectively solve the problems of wavelength locking and low polarization beam combining efficiency caused by the insufficient polarization state of quantum cascade laser, and can realize high-power dual-wavelength tunable output through polarization beam combining structure expansion;

[0007] The application provides a high-power external cavity tunable quantum cascade laser output module, comprising: a first laser, a first lens, a first half-wave plate and a first mid-infrared grating polarizer arranged in sequence along an optical path of the first laser; a second laser, a second lens, a second half-wave plate, a second mid-infrared grating polarizer and a third half-wave plate arranged in sequence along an optical path of the second laser; and a third mid-infrared grating polarizer, wherein the emergent light of the first mid-infrared grating polarizer and the third half-wave plate is converged on different surfaces of the third mid-infrared grating polarizer.

[0008] Further, by setting the inclination angle of the third mid-infrared grating polarizer, the transmission light of the third mid-infrared grating polarizer through which the emergent light of the first mid-infrared grating polarizer passes and the reflection light of the third half-wave plate on the surface of the third mid-infrared grating polarizer can be combined.

[0009] Further, the first and second Littrow gratings are arranged on the reflection light paths of the first and second mid-infrared grating polarizers, respectively.

[0010] Further, the installation angles of the first and second Littrow gratings are adjustable.

[0011] Further, the blaze angle of the Littrow grating is placed at the Littrow angle.

[0012] Further, the first and second lasers are quantum cascade lasers.

[0013] Further, the first and second lasers are fixed on an aluminum substrate after anodization treatment, and an indium sheet is arranged between the bottom of the first and second lasers and the aluminum substrate.

[0014] Further, the first and second lenses are aspherical lenses.

[0015] Further, the first and second lenses are coated with antireflection films on both surfaces.

[0016] Further, the first, second and third half-wave plates are rotatable half-wave plates.

[0017] The technical solution of this invention involves a beam emitted from a first laser, collimated by a first lens, and then incident on a first half-wave plate placed in front of a first mid-infrared grating polarizer. This allows for the adjustment of the P- and S- components in the beam. As the beam enters the first mid-infrared grating polarizer, the S-light cannot pass through the polarization separation film and undergoes total internal reflection, while the P-light is directly transmitted and output, then incident again on a third mid-infrared grating polarizer. Similarly, a beam emitted from a second laser, after being collimated by a second lens, is polarized using a second mid-infrared grating polarizer. The P-light output branch is converted into S-light by a third half-wave plate. The P-light passing through the first mid-infrared grating polarizer is transmitted through the third mid-infrared grating polarizer, while the S-light passing through the third half-wave plate is reflected by the third mid-infrared grating polarizer, thus achieving polarization combining at the third mid-infrared grating polarizer to obtain high-power output. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the aspherical lens of the present invention;

[0021] Figure 3 This is a schematic diagram of laser polarization beam combining of the two lasers of the present invention;

[0022] Figure 4 This is a schematic diagram of traditional polarization beam combining in the background technology;

[0023] Figure 5 This is a schematic diagram of a traditional Littrow external cavity tunable quantum cascade laser structure in the background art;

[0024] Explanation of reference numerals in the attached figures:

[0025] 11 - First laser; 12 - Second laser;

[0026] 21-First lens; 22-Second lens;

[0027] 31 - First half-wave plate; 32 - Second half-wave plate; 33 - Third half-wave plate;

[0028] 41-First mid-infrared grating polarizer; 42-Second mid-infrared grating polarizer; 43-Third mid-infrared grating polarizer;

[0029] 51 - First blazed grating; 52 - Second blazed grating. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Example 1

[0034] like Figures 1-3 As shown, the present invention provides a high-power external cavity tunable quantum cascade laser output module, comprising: a first laser 11, wherein a first lens 21, a first half-wave plate 31 and a first mid-infrared grating polarizer 41 are sequentially arranged along the optical path of the first laser 11; a second laser 12, wherein a second lens 22, a second half-wave plate 32, a second mid-infrared grating polarizer 42 and a third half-wave plate 33 are sequentially arranged along the optical path of the second laser 12; and a third mid-infrared grating polarizer 43, wherein the emitted light from the first mid-infrared grating polarizer 41 and the third half-wave plate 33 is respectively converged on different surfaces of the third mid-infrared grating polarizer 43.

[0035] The angle of the third mid-infrared grating polarizer 43 is such that the transmitted light from the first mid-infrared grating polarizer 41 is transmitted, and the transmitted light from the third half-wave plate 33 is reflected, thus achieving beam combining. The mid-infrared grating polarizer uses silicon as a substrate and is used to achieve beam polarization separation and beam combining.

[0036] The system also includes a first blazed grating 51 and a second blazed grating 52. The first blazed grating 51 is disposed on the reflected optical path of the first mid-infrared grating polarizer 41, and the second blazed grating 52 is disposed on the reflected optical path of the second mid-infrared grating polarizer 42. Both the first blazed grating 51 and the second blazed grating 52 can be installed with adjustable angles. The blaze angle of each blazed grating is optimized for the center wavelength band of the quantum cascade laser. The blaze angle of the blazed gratings is placed at the Littrow angle to form an optical feedback channel. The blazed gratings are used for wavelength locking and wavelength tuning of the quantum cascade laser. For S-beams, the S-beams cannot pass through the polarization separation film and undergo total internal reflection at the mid-infrared grating polarizer, then enter the blazed gratings placed at the Littrow angle to form optical feedback, achieving narrow linewidth and high side-mode suppression ratio. The selected wavelength can be changed by changing the grating angle. By fixing the angle of one grating and adjusting the angle of the other grating, high-power dual-wavelength tunable output can be achieved.

[0037] Both the first laser 11 and the second laser 12 are quantum cascade lasers. The quantum cascade lasers are packaged in a window package and fixed on an anodized aluminum substrate, with an indium sheet placed at their bottom within the aluminum substrate to facilitate heat dissipation.

[0038] Both the first lens 21 and the second lens 22 are aspherical lenses. Aspherical lenses can minimize spherical aberration, and both sides of the aspherical lenses (the first lens 21 and the second lens 22) are coated with corresponding anti-reflective coatings.

[0039] The first half-wave plate 31, the second half-wave plate 32, and the third half-wave plate 33 are all rotatable half-wave plates. Rotatable half-wave plates, also known as phase delayers, can cause a certain phase delay between the two polarization states of light in a beam. By changing the angle between the optical axis and the direction of the electric field of the output beam, the polarization state of the beam can be changed.

[0040] Working principle of the invention:

[0041] The beam emitted by the first laser 11 (quantum cascade laser) is collimated by the first lens 21 (aspherical lens) and then enters the first half-wave plate 31 (rotatable half-wave plate) placed in front of the first mid-infrared grating polarizer 41. Rotating the half-wave plate allows for adjustment of the proportion of P-ray and S-ray components in the beam. As the beam enters the first mid-infrared grating polarizer 41, the polarizer functions as polarization separator and polarization combiner. For S-rays, which cannot pass through the polarization separator, total internal reflection occurs at this point, and the beam enters the first blazed grating 51 placed at a Littrow angle, forming optical feedback. This achieves narrowed linewidth and high side-mode suppression ratio, and the selected wavelength can be changed by altering the grating angle. P-rays are directly transmitted and output, then re-enter and pass through the third mid-infrared grating polarizer 43.

[0042] Similarly, the beam emitted by the second laser 12 (quantum cascade laser), after being collimated by the second lens 22 (aspherical lens), is also polarized using the second mid-infrared grating polarizer 42, and the S-beam is totally internally reflected and directed into the second blazed grating 52 placed at the Littrow angle for external cavity feedback. Unlike before, for polarization combining, a third half-wave plate 33 (rotatable half-wave plate) is inserted into the output branch of the P-beam to convert the P-beam into the S-beam. High-power output is obtained by polarization combining the P-beam previously transmitted through the first mid-infrared grating polarizer 41 and the third mid-infrared grating polarizer 43 at the polarization plane.

[0043] Furthermore, by fixing the angle of one blazed grating and adjusting the angle of the other blazed grating, high-power dual-wavelength tunable output can be achieved.

[0044] This invention can effectively solve the problems of wavelength locking and low polarization combining efficiency caused by insufficient polarization state in quantum cascade lasers, and can realize narrow linewidth output and wavelength tuning of quantum cascade lasers. It can even achieve high-power dual-wavelength tunable output through polarization combining structure expansion.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power external cavity tunable quantum cascade laser output module, characterized in that, include: A first laser, along the optical path of the first laser, is provided with a first lens, a first half-wave plate and a first mid-infrared grating polarizer in sequence; The second laser has a second lens, a second half-wave plate, a second mid-infrared grating polarizer, and a third half-wave plate arranged sequentially along its optical path. The third mid-infrared grating polarizer, the light emitted from the first mid-infrared grating polarizer and the third half-wave plate are respectively focused on different surfaces of the third mid-infrared grating polarizer; By setting the tilt angle of the third mid-infrared grating polarizer, the transmitted light from the first mid-infrared grating polarizer passing through the third mid-infrared grating polarizer and the reflected light from the third half-wave plate on the surface of the third mid-infrared grating polarizer can be combined. It also includes a first blazed grating and a second blazed grating, wherein the first blazed grating is disposed in the reflected light path of the first mid-infrared grating polarizer, and the second blazed grating is disposed in the reflected light path of the second mid-infrared grating polarizer.

2. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that, The mounting angles of both the first and second blazed gratings are adjustable.

3. The high-power external cavity tunable quantum cascade laser output module according to claim 2, characterized in that, The blaze angle of the blaze grating is set at the Littrow angle.

4. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that, Both the first laser and the second laser are quantum cascade lasers.

5. The high-power external cavity tunable quantum cascade laser output module according to claim 4, characterized in that, The first laser and the second laser are fixed on an anodized aluminum substrate, and an indium sheet is disposed between their bottom and the aluminum substrate.

6. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that, Both the first lens and the second lens are aspherical lenses.

7. The high-power external cavity tunable quantum cascade laser output module according to claim 6, characterized in that, Both sides of the first lens and the second lens are coated with anti-reflective coatings.

8. The high-power external cavity tunable quantum cascade laser output module according to claim 1, characterized in that, The first half-wave plate, the second half-wave plate, and the third half-wave plate are all rotatable half-wave plates.

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