A terahertz vector vortex quantum cascade laser and its preparation method

Abstract

The present invention relates to a terahertz vector vortex quantum cascade laser, comprising a substrate, a bonding metal layer located above the substrate, a seed laser region and a bus waveguide arranged along the length direction of the laser and connected to each other are arranged above the bonding metal layer, a resonant ring and a transition electrode arranged along the length direction of the laser and spaced apart from each other are arranged on one side of the bus waveguide, a metal air bridge is set between the resonant ring and the transition electrode, and an absorption boundary is set at the end of the seed laser region and the end of the bus waveguide. The present invention also provides a method for preparing a terahertz vector vortex quantum cascade laser, which can directly emit a terahertz vector vortex laser with a high mode purity, can realize a hollow annular far-field light spot, and the emitted vector vortex light can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum, and the polarization characteristic is angular polarization, which has the advantages of high stability, high excitation efficiency, narrow line width, and high side mode suppression ratio.

Description

Technical Field

[0001] The present invention relates to the field of terahertz quantum cascade lasers, and more specifically to a terahertz vector vortex quantum cascade laser and a preparation method thereof. Background Art

[0002] Terahertz (THz) quantum cascade lasers (QCL) have become a highly potential coherent light source in the range of 2-5 THz due to their high energy conversion efficiency, small size, easy integration, and electric pumping. They have important applications in imaging, material detection, and communications. For example, in imaging and material detection, because the intrinsic vibrational energy levels of a large number of molecules and clusters are in the THz band, this band is also called the fingerprint spectrum of molecules. The THz imaging technology using this characteristic has been applied in the fields of molecular spectroscopy, biomedicine, security, and non-destructive testing. In terms of communications, THz wireless communications have the advantages of wide bandwidth, high confidentiality, and the ability to penetrate plasma layers, and can become another important communication frequency band after microwave and optical communications.

[0003] by (l is the topological charge, i is the imaginary unit, Electromagnetic waves with phase distribution in the form of angular coordinates have orbital angular momentum. Due to its spiral wavefront, it is called vortex light. Vortex light is used in STED technology, which can break the diffraction limit and reduce the resolution to the nanometer level. In addition, through the encoding and multiplexing of orbital angular momentum, an unlimited number of channels can be added at the same communication frequency in theory. Vortex light can be divided into scalar vortex light and vector vortex light. The polarization of the scalar vortex field is uniform and the same everywhere in space, while the polarization of the vector vortex field changes with the spatial position.

[0004] At present, vortex light is mostly generated by discrete devices, which has the disadvantage of unstable optical path assistance. Integrated vortex light emitters are concentrated in the visible light and communication bands, and there is no laser that can directly generate vortex light in the terahertz band. Therefore, there is an urgent need for a laser that can vortex-control the phase of the terahertz wave to directly generate a stable scalar vortex terahertz wave. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a terahertz vector vortex quantum cascade laser and a preparation method thereof, which can directly emit vector vortex terahertz waves and has the advantage of high stability, so that the emitted vector vortex terahertz waves have higher mode purity.

[0006] A terahertz vector vortex quantum cascade laser provided by the present invention comprises a substrate and a bonding metal layer located above the substrate, a seed laser region and a bus waveguide arranged along the length direction of the laser and connected to each other are provided above the bonding metal layer, and a resonant ring and a transition electrode are provided on one side of the bus waveguide, arranged along the length direction of the laser and spaced apart from each other, a metal air bridge is constructed between the resonant ring and the transition electrode, and absorption boundaries are provided at the ends of the seed laser region and the ends of the bus waveguide.

[0007] Furthermore, the seed laser region includes a first active region and a first top metal layer from bottom to top, and the first active region has a periodic grating structure.

[0008] Furthermore, the periodic grating structure is composed of a number of long strip gratings of the same size, and the long strip gratings are equidistantly spaced.

[0009] Furthermore, the bus waveguide includes a gradual change zone and a holding zone, the width of the gradual change zone gradually decreases from the seed laser zone to the holding zone, and the holding zone is a long strip region with a constant width.

[0010] Furthermore, the gradual change zone has a starting side and a terminating side, the width of the starting side matches the width of the seed laser zone, and the width of the terminating side matches the width of the holding zone.

[0011] Furthermore, the resonant ring includes a third active region and a third top metal layer in sequence from bottom to top, and the third top metal electrode has a periodic double-slit structure.

[0012] Furthermore, the periodic double slit structure is composed of a plurality of groups of double slits which are equally spaced and circumferentially arranged at a certain angle, and each group of double slits is composed of two single slits whose length directions point to the axis of the resonant ring.

[0013] The present invention also provides a method for preparing a terahertz vector vortex quantum cascade laser, comprising:

[0014] Step S1, preparing a substrate having a bonding metal layer and an active region layer.

[0015] Step S2, forming an absorption edge pattern on a substrate having a bonding metal layer and an active region layer.

[0016] Step S3, forming a periodic grating pattern on the surface of the active region layer in the absorption edge pattern region, and etching the active region layer having the periodic grating pattern to obtain periodic grating slits.

[0017] Step S4, making an electrode pattern on the surface of the active region layer after the step S3, and growing metal on the photolithographic electrode pattern, and forming a top metal layer after peeling.

[0018] Step S5, using photoresist as a mask for the top metal layer, etching the area of ​​the active layer not covered by the photoresist to expose the bonding metal layer, and completing the production of the seed laser region, bus waveguide, resonant ring, transition electrode and absorption boundary.

[0019] Step S6, making a metal air bridge between the resonant ring and the transition electrode.

[0020] Furthermore, the step S1 comprises:

[0021] Step S11, preparing a first substrate having a first metal layer; including: providing a first base, epitaxially growing a corrosion barrier layer on the surface of the first base, epitaxially growing an upper contact layer on the corrosion barrier layer, epitaxially growing an active area layer on the upper contact layer, epitaxially growing a lower contact layer on the active area layer, and then forming a first metal layer on the lower contact layer.

[0022] Step S12, preparing a second substrate having a second metal layer; comprising: providing a second substrate, and forming a second metal layer on a surface of the second substrate.

[0023] Step S13: bonding the first metal layer and the second metal layer together to form a bonding metal layer.

[0024] Step S14, corroding the first substrate to expose the corrosion barrier layer, and then removing the corrosion barrier layer, and the second substrate serves as the substrate.

[0025] Further, the step S6 comprises:

[0026] Step S61, filling the gap between the resonant ring and the transition electrode with photoresist, so that the surfaces of the top metal layer of the resonant ring and the top metal layer of the transition electrode have photoresist of a certain width.

[0027] Step S62: baking the photoresist at a high temperature to deform and bulge the photoresist on the top metal layer of the resonant ring and the top metal layer of the transition electrode.

[0028] Step S63, forming a photoresist inverted mesa, and growing metal on the deformed and arched photoresist surface.

[0029] Step S64, applying glue to protect the top of all areas after step S63, thinning the substrate after step S63 by chemical etching, and then growing metal behind the thinned substrate.

[0030] Step S65, stripping off the excess metal and removing the filled photoresist to prepare a metal air bridge.

[0031] The present invention can directly emit terahertz vector vortex laser with higher mode purity through electric pumping, and can realize a hollow annular far-field light spot. The emitted vector vortex light can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum. The polarization characteristic is angularly polarized light, and it has the advantages of high stability, high excitation efficiency, narrow line width, and high side mode suppression ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the terahertz vector vortex quantum cascade laser according to the present invention.

[0033] Figure 2 yes Figure 1 Schematic diagram of the structure of the seed laser region.

[0034] Figure 3 yes Figure 1 Schematic diagram of the structure of the bus waveguide.

[0035] Figure 4 It is a flow chart of the method for preparing the terahertz vector vortex quantum cascade laser according to the present invention.

[0036] Figure 5 yes Figure 1 Flow chart of the preparation of metal air bridge.

[0037] Figure 6 This is the LIV test result of the terahertz vector vortex quantum cascade laser according to the present invention.

[0038] Figure 7 It is a spectrum diagram of the terahertz vector vortex quantum cascade laser under different pump currents according to the present invention.

[0039] Figure 8 It is a mode purity diagram of the topological charge of vortex light emitted by the terahertz vector vortex quantum cascade laser according to the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0041] like Figure 1As shown, the terahertz vector vortex quantum cascade laser provided by the present invention adopts a bimetallic waveguide structure, including a substrate 1, a bonding metal layer 2 is provided above the substrate 1, a seed laser region 3 and a bus waveguide 4 arranged along the length direction of the laser and connected to each other are provided above the bonding metal layer 2, a resonant ring 5 and a transition electrode 6 arranged along the length direction of the laser and spaced apart from each other are provided on one side of the bus waveguide 4, the resonant ring 5 and the transition electrode 6 are both provided above the bonding metal layer 2, and a metal air bridge 7 is provided between the resonant ring 5 and the transition electrode 6. In addition, an absorption boundary 8 is provided at the end of the seed laser region 3 and the end of the bus waveguide 4.

[0042] The seed laser region 3 is rectangular in shape as a whole. Figure 2 As shown, it includes a first active area 31 and a first top metal layer 32 from bottom to top. The first active area 31 has a periodic grating structure 311, which is composed of a number of long strip gratings of the same size, and these long strip gratings are equidistantly spaced. The periodic grating structure 311 is formed by first etching a number of grating slits of the same size in the first active area 31, and then growing gold on the surface of the first active area 31. When growing gold, the metal enters the grating slits to form the grating structure 311, and the remaining metal that does not enter the grating slits grows on the surface of the first active area 31 as the first top metal layer 32. The number of long strip gratings in the periodic grating structure 311 is 60-100, the spacing between two adjacent long strip gratings is 8μm-22μm, the length of each long strip grating is 150μm-250μm, the width is 8μm, and the height (i.e., the corrosion depth of the first active area 13) is 600nm. If the vortex light frequency excited by the laser of the present invention is designed to be 3.45THz, the number of long strip gratings is designed to be 60, the spacing between two adjacent long strip gratings is designed to be 12.1um, the length of each long strip grating is designed to be 150μm-250μm, the length is designed to be 8μm, and the height is designed to be 600nm. At the same time, adding a π phase shift of one quarter of the wavelength of the vortex light at the center of the grating can improve the Q value of the distributed feedback structure, so that the frequency of the lasing works at the forbidden center of the photon energy band and maintains the single-mode characteristic.

[0043] Reference again Figure 1, the bus waveguide 4 includes a gradient zone 41 and a holding zone 42. The width of the gradient zone 41 gradually decreases from the seed laser zone 3 to the holding zone 42, and the holding zone 42 is a long strip area with a constant width. The gradient zone 41 has a starting side 411 and a termination side 412, the width of the starting side 411 matches the width of the seed laser zone 3, and the width of the termination side 42 matches the width of the holding zone 42. The gradient zone 41 tapers to a distance of 1000μm-1600μm, that is, the distance between the starting side 411 and the termination side 412 is 1000μm-1600μm. The length of the holding zone 42 is 500μm-1000μm, and the width is 10μm. Taking the width of the seed laser region 3 as 150 μm as an example, the bus waveguide 4 gradually shrinks from 150 μm to 1000 μm-1600 μm and then transmits 500 μm-1000 μm while maintaining the width of 10 μm. The specific structure of the bus waveguide 4 is as follows: Figure 3 As shown, from bottom to top, it includes a second active area 43 and a second top metal layer 44. Part of the second active area 43 and part of the second top metal layer 44 are in a trapezoidal shape, and the short sides of the trapezoidal parts together constitute the above-mentioned starting side 411, and the long sides together constitute the above-mentioned terminating side 412. In addition, the second top metal layer 44 is used for wiring to provide electrical pumping.

[0044] Reference again Figure 1 The resonant ring 5 includes a third active region 51 and a third top metal layer 52 from bottom to top. The third top metal electrode 52 has a periodic double slit structure. The periodic double slit structure is composed of a plurality of groups of double slits that are equally spaced and arranged circumferentially at a certain angle, and each group of double slits is composed of two single slits whose length directions point to the axis of the resonant ring. The width of a single slit is between 2μm and 6μm, and the length is between 8μm and 14μm.

[0045] Since the radius r of the resonant ring 5 and the order N of its whispering gallery mode satisfy: k0×n eff ×r=N, where k0 is the wave vector in vacuum, n effis the effective refractive index. Therefore, by adjusting the radius r of the resonant ring 5, the order N of its whispering gallery mode can be adjusted. In addition, the topological charge of the target vector vortex light is related to the number M of the above-mentioned double slits, that is, the topological charge of the decomposed left-handed / right-handed circularly polarized vortex light is N-M+1 / NM-1 respectively. In actual design, the spacing between the resonant ring 5 and the bus waveguide 4 can be adjusted to improve the coupling efficiency, and the angle θ between the two single slits of each set of double slits is designed to be one-quarter of the effective wavelength to suppress the reverse whispering gallery mode and improve the coupling efficiency and mode purity of the vortex laser. Taking the excitation of the 3rd order / 1st order left-handed / right-handed circularly polarized vortex light as an example, the required parameters at this time are as follows: r=170.1μm, N=40, M=38, θ=2.34°. The fixed-frequency seed laser generated by the seed laser 3 is coupled to the resonant ring 5 through the bus waveguide 4 to excite the whispering gallery mode of the resonant ring 5. Since the radiation unit of the resonant ring 5 is composed of periodic double slits, and the number of double slits and the order of the whispering gallery mode of the resonant ring have a fixed difference, the emitted laser has a fixed phase difference, which is conducive to constructing the phase distribution of the vortex light.

[0046] The transition electrode 6 is located at Figure 1 The right side of the resonant ring 5 in FIG. 1 (i.e., the side close to the seed laser 3) includes a fourth active region 61 and a fourth top metal layer 62 from bottom to top, which are used to provide electrical pumping to the resonant ring 5 through the metal air bridge 7. The transition electrode 6 is a square with a side length of 100 μm-400 μm, and the distance between the transition electrode 6 and the resonant ring 5 is 5 μm-70 μm.

[0047] The metal air bridge 7 is an arched metal structure with air underneath, and is used to connect the resonant ring 5 and the transition electrode 6. The length and width of the metal air bridge 7 are 5 μm-70 μm and 4 μm-30 μm respectively. The absorption boundary 8 includes a fifth active region, and is used to absorb excess electromagnetic fields. It should be noted that the above-mentioned first active area 31, second active area 43, third active area 51, fourth active area 61 and fifth active area are the same active area (that is, the top surfaces of the first active area 31, the second active area 43, the third active area 51, the fourth active area 61 and the fifth active area are at the same height), and are prepared in one step. The above-mentioned first top metal layer 32, second top metal layer 44, third top metal layer 52 and fourth top metal layer 62 are also the same metal layer (that is, the top surface and bottom surface of the first top metal layer 32, the second top metal layer 44, the third top metal layer 52 and the fourth top metal layer 62 are at the same height), and are prepared in one step. For the convenience of explanation, they are distinguished.

[0048] The method for preparing the above-mentioned terahertz vector vortex quantum cascade laser is described below.

[0049] like Figure 4As shown, the method for preparing the terahertz vector vortex quantum cascade laser provided by the present invention comprises the following steps:

[0050] Step S1, preparing a substrate 1 having a bonding metal layer 2 and an active region layer. The process comprises:

[0051] Step S11, preparing a first substrate having a first metal layer: providing a first substrate, epitaxially growing a corrosion barrier layer on the surface of the first substrate, epitaxially growing an upper contact layer on the corrosion barrier layer, epitaxially growing an active region layer on the upper contact layer, epitaxially growing a lower contact layer on the active region layer, and then forming a first metal layer on the lower contact layer. The active region layer comprises 90 periodically repeated modules, each module comprising 9 overlapping layers of GaAs potential wells and 9 layers of Al 0.15 Ga 0.85 The thickness of the As barrier starting from GaAs is: 11.4, 2.0, 12.0, 2.0, 12.2, 1.8, 12.8, 1.5, 15.8, 0.6, 9.0, 0.6, 14.0, 3.8, 11.6, 3.5, 11.3, 2.7 (nm). The first two layers of GaAs are doped layers with an n-type doping concentration of 10 16 cm -3 .

[0052] Step S12, preparing a second substrate having a second metal layer: providing a second substrate, and forming a second metal layer on a surface of the second substrate.

[0053] Step S13, bonding the first metal layer and the second metal layer together to form a bonding metal layer. The bonding metal layer obtained at this time corresponds to the bonding metal layer 2 mentioned above.

[0054] Step S14, the first substrate is corroded to expose the corrosion barrier layer, and then the corrosion barrier layer is removed with an acid solution (such as HF acid or concentrated hydrochloric acid). At this time, the second substrate with the second metal layer is retained to form the above-mentioned substrate 1, and the substrate 1 with the bonding metal layer 2 and the active area layer is prepared.

[0055] Step S2, forming an absorption edge pattern on the substrate having the bonding metal layer and the active region layer. The absorption edge pattern is a boundary pattern formed by the periphery of the seed laser region 3, the bus waveguide 4, the resonant ring 5, the transition electrode 6, and the absorption boundary 8.

[0056] Step S3, using photolithography technology to produce a periodic grating pattern on the surface of the active area layer in the absorption edge pattern area, and using a sulfuric acid system etching solution to etch the active area layer with the periodic grating pattern to obtain periodic grating slits. At this time, the active area with the periodic grating slits corresponds to the first active area 31. The etching depth is calibrated by a step profiler. After the etching is completed, the photoresist on the surface of the active area layer needs to be removed.

[0057] Step S4, using photolithography technology to make an electrode pattern on the surface of the active area layer with periodic grating slits, and using electron beam evaporation, magnetron sputtering or thermal evaporation to grow metal on the photolithographic electrode pattern, and after stripping the photoresist, a top metal layer is formed. The top metal layer at this time corresponds to the first top metal layer 32, the second top metal layer 44, the third top metal layer 52 and the fourth top metal layer 62. Among them, the third top metal layer 52 has a double slit pattern.

[0058] Step S5, using the photoresist as a mask for the top metal layer, the region of the active region layer not covered by the photoresist is etched to expose the bonding metal layer. It should be noted that the photoresist used as a mask is 5um wider than the top metal layer and the absorption boundary in step S2 to protect the top metal layer and the absorption boundary. After etching, the photoresist on the surface of the active region layer is removed. At this point, the seed laser region 3, bus waveguide 4, resonant ring 5, transition electrode 6 and absorption boundary 8 are completed.

[0059] Step S6, making a metal air bridge 7 between the resonant ring 5 and the transition electrode 6. The process of making the metal air bridge 7 is as follows: Figure 5 As shown, including:

[0060] Step S61, using a low-speed coating process, fills the gap between the resonant ring 5 and the transition electrode 6 with photoresist, so that the surfaces of the third top metal layer 52 of the resonant ring 5 and the fourth top metal layer 62 of the transition electrode 6 have a certain width of photoresist.

[0061] Step S62 , baking the photoresist at a high temperature (140° C.) for a period of time (eg, 15 minutes) to deform and bulge the photoresist on the surfaces of the third top metal layer 52 and the fourth top metal layer 62 .

[0062] Step S63, using a reverse photoresist process to form a photoresist inverted mesa 71, and using an electron beam evaporation method to grow metal on the deformed and raised photoresist surface.

[0063] Step S64, top coating of all areas after step S63 is performed for protection, and the substrate 1 after step S63 is thinned to about 200 μm by citric acid chemical etching, and then metal is grown behind the thinned substrate 1 to improve heat dissipation. Chemical etching is selected to avoid compressing the air bridge metal on the top.

[0064] Step S65, stripping off the excess metal in acetone, and removing the filled photoresist with a degumming solution, and finally preparing Figure 5 Metal air bridge in 7.

[0065] By utilizing the present invention, a terahertz scalar vortex laser with high mode purity can be obtained. The performance of the laser of the present invention is described in detail below through experimental results.

[0066] Figure 6 The LIV test results of the terahertz vector vortex quantum cascade laser of the present invention at different temperatures are shown, and the results are measured in a pulse mode with a repetition frequency of 60kHz and a pulse width of 1μs. The laser and the resonant ring are pumped simultaneously in the test. It can be seen from the figure that the maximum output power of the above device is 5.78mW at 20K and 3.78mW at 77K.

[0067] Figure 7 The test results of the spectral characteristics of the terahertz vector vortex quantum cascade laser of the present invention are shown. The pumping conditions are: the laser and the resonant ring are pumped simultaneously, with a pulse mode of a repetition frequency of 60kHz and a pulse width of 1μs. The test temperature is 77K. It can be seen from the figure that the laser starts from the threshold current and maintains a single-mode characteristic as the current increases until a multi-mode characteristic appears at the peak current. The central frequency of the laser lasing is f=3.445THz.

[0068] Figure 8 The figure shows the mode purity of the left-handed / right-handed circularly polarized vortex light after the vortex light emitted by the laser is separated. It can be concluded that the topological charge of the left-handed / right-handed circularly polarized vortex light is 3 and 1 respectively. This result is consistent with the theoretical design (40-order whispering gallery mode and 38 scattering elements), and its mode purity is as high as 87.7% and 91% respectively.

[0069] It can be seen that the present invention can realize a hollow annular far-field light spot, and the emitted vector vortex light can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum, and has the characteristics of high mode purity, narrow linewidth, and high side mode suppression ratio.

[0070] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A terahertz vector vortex quantum cascade laser, comprising a substrate and a bonding metal layer located above the substrate, characterized in that: A seed laser region and a bus waveguide are arranged along the length direction of the laser and connected to each other, and a resonant ring and a transition electrode are arranged on one side of the bus waveguide, arranged along the length direction of the laser and spaced apart from each other, a metal air bridge is set between the resonant ring and the transition electrode, and an absorption boundary is set at the end of the seed laser region and the end of the bus waveguide; The seed laser region includes a first active region and a first top metal layer from bottom to top, wherein the first active region has a periodic grating structure; the periodic grating structure is composed of a plurality of long strip gratings of the same size, and the long strip gratings are equidistantly spaced; The bus waveguide includes a gradual change zone and a holding zone, the width of the gradual change zone gradually decreases from the seed laser zone to the holding zone, and the holding zone is a long strip region with a constant width; the gradual change zone has a starting side and a terminating side, the width of the starting side matches the width of the seed laser zone, and the width of the terminating side matches the width of the holding zone; The resonant ring includes a third active area and a third top metal layer from bottom to top, and the third top metal layer has a periodic double slit structure; the periodic double slit structure is composed of a plurality of groups of double slits that are equally spaced and circumferentially arranged at a certain angle, and each group of double slits is composed of two single slits whose length directions point to the axis of the resonant ring.

2. A method for preparing a terahertz vector vortex quantum cascade laser as claimed in claim 1, characterized in that: include: Step S1, preparing a substrate having a bonding metal layer and an active area layer; Step S2, forming an absorption edge pattern on a substrate having a bonding metal layer and an active region layer; Step S3, making a periodic grating pattern on the surface of the active region layer in the absorption edge pattern area, and etching the active region layer with the periodic grating pattern to obtain a periodic grating slit; Step S4, making an electrode pattern on the surface of the active area layer after the step S3, and growing metal on the photolithographic electrode pattern, and forming a top metal layer after peeling; Step S5, using the photoresist as a mask for the top metal layer, etching the area of ​​the active layer not covered by the photoresist to expose the bonding metal layer, and completing the production of the seed laser region, bus waveguide, resonant ring, transition electrode and absorption boundary; Step S6, making a metal air bridge between the resonant ring and the transition electrode.

3. The method for preparing a terahertz vector vortex quantum cascade laser according to claim 2, characterized in that: The step S1 comprises: Step S11, preparing a first substrate having a first metal layer; comprising: providing a first substrate, epitaxially growing a corrosion barrier layer on the surface of the first substrate, epitaxially growing an upper contact layer on the corrosion barrier layer, epitaxially growing an active region layer on the upper contact layer, epitaxially growing a lower contact layer on the active region layer, and then forming a first metal layer on the lower contact layer; Step S12, preparing a second substrate having a second metal layer; comprising: providing a second substrate, and forming a second metal layer on a surface of the second substrate; Step S13, bonding the first metal layer and the second metal layer together to form a bonding metal layer; Step S14, corroding the first substrate to expose the corrosion barrier layer, and then removing the corrosion barrier layer, and the second substrate serves as the substrate.

4. The method for preparing a terahertz vector vortex quantum cascade laser according to claim 2, characterized in that: The step S6 comprises: Step S61, filling the gap between the resonant ring and the transition electrode with photoresist, so that the top metal layer of the resonant ring and the top metal layer of the transition electrode have a certain width of photoresist on their surfaces; Step S62, baking the photoresist at a high temperature to deform and arch the photoresist on the top metal layer of the resonant ring and the top metal layer of the transition electrode; Step S63, forming a photoresist inverted surface and growing metal on the deformed and arched photoresist surface; Step S64, applying glue to all regions after step S63 for protection, thinning the substrate after step S63 by chemical etching, and then growing metal behind the thinned substrate; Step S65, stripping off the excess metal and removing the filled photoresist to prepare a metal air bridge.

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