CN113594857A - Terahertz vector vortex quantum cascade laser and preparation method thereof - Google Patents

Abstract

The invention relates to a terahertz vector vortex quantum cascade laser which comprises a substrate and a bonding metal layer positioned above the substrate, wherein a seed laser area and a bus waveguide which are arranged along the length direction of the laser and are connected with each other are arranged above the bonding metal layer, a resonance ring and a transition electrode which are arranged along the length direction of the laser and are separated from each other are arranged on one side of the bus waveguide, a metal air bridge is erected between the resonance ring and the transition electrode, and absorption boundaries are arranged at the end part of the seed laser area and the end part of the bus waveguide. The invention also provides a preparation method of the terahertz vector vortex quantum cascade laser, the terahertz vector vortex laser with higher mode purity can be directly emitted, hollow annular far-field light spots can be realized, the emitted vector vortex optical rotation can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum, the polarization characteristic is angular polarization, and the terahertz vector vortex quantum cascade laser has the advantages of high stability, high excitation efficiency, narrow linear width and high side mode suppression ratio.

Description

Terahertz vector vortex quantum cascade laser and preparation method thereof

Technical Field

The invention relates to the field of terahertz quantum cascade lasers, in particular to a terahertz vector vortex quantum cascade laser and a preparation method thereof.

Background

Due to the advantages of high energy conversion efficiency, small size, easy integration, electric pumping and the like, the terahertz (THz) Quantum Cascade Laser (QCL) becomes a coherent light source with great potential in the range of 2-5THz, and has important application in the fields of imaging, material detection, communication and the like. For example, in the imaging and material detection, because the intrinsic vibrational energy levels of a large number of molecules and clusters are in the terahertz band, the band is also called the fingerprint spectrum band of molecules, and the terahertz imaging technology utilizing the characteristic has been applied to the fields of molecular spectroscopy, biomedicine, safety, nondestructive inspection and the like. In the aspect of communication, terahertz wireless communication has the advantages of wide bandwidth, high confidentiality, plasma layer penetrability and the like, and can become another important communication frequency band for relaying microwave and optical communication.

To be provided with

(l is the number of topological charges, i is the unit of imaginary numbers,

angular coordinates) has orbital angular momentum, and is called vortex rotation due to its spiral wave front. Vortex light is used for the STED technology, and can break through the diffraction limit, so that the resolution is reduced to the nanometer level. In addition, by encoding and multiplexing of orbital angular momentum, an infinite number of channels can be theoretically added to the same communication frequency. Vortex light can be divided into scalar vortex light and vector vortex rotation light, the polarization of a scalar vortex field is uniform and is identical everywhere in space, and the polarization of a vector vortex field changes along with the space position.

At present, the eddy rotation is mostly generated by a discrete device, and has the defect of unstable light path assistance. The integrated vortex light emitters are all concentrated on visible light and communication bands, and no laser capable of directly generating vortex optical rotation exists in terahertz bands. Therefore, there is a need for a laser capable of performing vortex control on the phase of a terahertz wave to directly generate a stable scalar vortex terahertz wave.

Disclosure of Invention

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

The invention provides a terahertz vector vortex quantum cascade laser which comprises a substrate and a bonding metal layer positioned above the substrate, wherein a seed laser area and a bus waveguide which are arranged along the length direction of the laser and are connected with each other, a resonant ring and a transition electrode which are arranged on one side of the bus waveguide, are arranged along the length direction of the laser and are separated from each other, a metal air bridge is erected between the resonant ring and the transition electrode, and absorption boundaries are arranged at the end part of the seed laser area and the end part of the bus waveguide.

Further, the seed laser region comprises a first active region and a first top metal layer from bottom to top, and the first active region is provided with a periodic grating structure.

Furthermore, the periodic grating structure is composed of a plurality of long-strip-shaped gratings with the same size, and the long-strip-shaped gratings are spaced at equal intervals.

Further, the bus waveguide comprises a gradual change region and a holding region, the width of the gradual change region is gradually reduced from the seed laser region to the holding region, and the holding region is an elongated region with a constant width.

Further, the transition region has a start side having a width matching the width of the seed laser region and an end side having a width matching the width of the holding region.

Further, the resonant ring sequentially comprises a third active region and a third top metal layer from bottom to top, and the third top metal electrode has a periodic double-slit structure.

Furthermore, the periodic double-slit structure is composed of a plurality of groups of double slits which are equidistantly arranged and are circumferentially arranged at a certain angle, and each group of double slits is composed of two single slits with the length direction pointing to the axis of the resonance ring.

The invention also provides a preparation method of the terahertz vector vortex quantum cascade laser, which comprises the following steps:

step S1, a substrate having a bonding metal layer and an active region layer is prepared.

In step S2, an absorption edge pattern is formed on a substrate having a bonding metal layer and an active region layer.

Step S3, a periodic grating pattern is formed on the surface of the active area layer in the absorption edge pattern area, and the active area layer having the periodic grating pattern is etched to obtain a periodic grating slit.

And step S4, forming an electrode pattern on the surface of the active region layer after the step S3, growing metal on the electrode pattern after photoetching, and forming a top metal layer after stripping.

And step S5, taking the photoresist as a mask of the top metal layer, etching the region of the active region layer which is not covered by the photoresist to expose the bonding metal layer, and manufacturing and finishing the seed laser region, the bus waveguide, the resonance ring, the transition electrode and the absorption boundary.

Step S6, a metal air bridge is fabricated between the resonance ring and the transition electrode.

Further, the step S1 includes:

step S11, preparing a first substrate having a first metal layer; the method comprises the following steps: the method comprises the steps of 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 forming a first metal layer on the lower contact layer.

Step S12, preparing a second substrate having a second metal layer; the method comprises the following steps: and providing a second substrate, and forming a second metal layer on the surface of the second substrate.

Step S13, bonding the first metal layer and the second metal layer together to form a bonding metal layer.

And step S14, etching the first base to expose the corrosion barrier layer, and removing the corrosion barrier layer, wherein the second base is used as the substrate.

Further, the step S6 includes:

step S61, filling photoresist into the gap between the resonant ring and the transition electrode, 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.

And step S62, baking the photoresist at 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.

And step S63, forming a photoresist inverted mesa, and growing metal on the deformed and arched photoresist surface.

And step S64, performing top gluing protection on all the areas subjected to the step S63, thinning the substrate subjected to the step S63 through chemical corrosion, and growing metal on the back of the thinned substrate.

And step S65, stripping the redundant metal and removing the filled photoresist to prepare the metal air bridge.

The terahertz vector vortex laser with high mode purity can be directly emitted through the electric pump, a hollow annular far-field light spot can be realized, the emitted vector vortex optical rotation can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum, the polarization characteristic is angular polarized light, and the terahertz vector vortex laser has the advantages of high stability, high excitation efficiency, narrow line width and high side mode suppression ratio.

Drawings

Fig. 1 is a schematic structural diagram of a terahertz vector vortex quantum cascade laser according to the invention.

Fig. 2 is a schematic structural diagram of the seed laser region in fig. 1.

Fig. 3 is a schematic diagram of the structure of the bus waveguide of fig. 1.

FIG. 4 is a flow chart of a method for manufacturing a terahertz vector vortex quantum cascade laser according to the invention.

FIG. 5 is a flow chart of the preparation of the metal air bridge of FIG. 1.

FIG. 6 is an L-I-V test result of a terahertz vector vortex quantum cascade laser according to the invention.

FIG. 7 is a spectrum diagram of a terahertz vector vortex quantum cascade laser according to the invention under different pumping currents.

FIG. 8 is a mode purity diagram of the topological charge number of the terahertz vector vortex quantum cascade laser emission vortex rotation according to the invention.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the terahertz vector vortex quantum cascade laser provided by the invention adopts a bimetal waveguide structure, and comprises a substrate 1, a bonding metal layer 2 is arranged above the substrate 1, a seed laser region 3 and a bus waveguide 4 which are arranged along the length direction of the laser and are connected with each other are arranged above the bonding metal layer 2, a resonance ring 5 and a transition electrode 6 which are arranged along the length direction of the laser and are spaced from each other are arranged on one side of the bus waveguide 4, the resonance ring 5 and the transition electrode 6 are both arranged above the bonding metal layer 2, and a metal air bridge 7 is erected between the resonance ring 5 and the transition electrode 6. An absorption boundary 8 is provided at an end of the seed laser region 3 and an end of the bus waveguide 4.

The seed laser region 3 is rectangular as a whole and includes, as shown in fig. 2, a first active region 31 and a first top metal layer 32 from bottom to top. The first active region 31 has a periodic grating structure 311, and the periodic grating structure 311 is composed of a plurality of elongated gratings with the same size, and the elongated gratings are spaced at equal intervals. The periodic grating structure 311 is formed in the following manner: firstly, a plurality of grating slits with the same size are etched in the first active region 31, then gold is grown on the surface of the first active region 31, when the gold is grown, the metal enters the grating slits to form a grating structure 311, and the rest of the metal which does not enter the grating slits grows into a first top metal layer 32 on the surface of the first active region 31. The number of the elongated gratings in the periodic grating structure 311 is 60-100, the distance between two adjacent elongated gratings is 8 μm-22 μm, the length of each elongated grating is 150 μm-250 μm, the width is 8 μm, and the height (i.e., the etching depth of the first active region 13) is 600 nm. If the frequency of vortex light excited by the laser is designed to be 3.45THz, the number of the strip-shaped gratings is designed to be 60, the distance between two adjacent strip-shaped gratings is designed to be 12.1um, the length of each strip-shaped grating is designed to be 150-250 mu m, the length of each strip-shaped grating is designed to be 8 mu m, and the height of each strip-shaped grating is designed to be 600 nm. Meanwhile, the pi phase shift of one-fourth vortex light wavelength is added to the center of the grating, so that the Q value of a distributed feedback structure can be improved, the lasing frequency works in the forbidden band center of a photon energy band, and the single-mode characteristic is kept.

Referring again to fig. 1, the bus waveguide 4 includes a tapered region 41 and a holding region 42. The width of the gradual change region 41 is gradually reduced from the seed laser region 3 to the holding region 42, and the holding region 42 is an elongated region with a constant width. The gradation region 41 has a start side 411 and an end side 412, the width of the start side 411 matching the width of the seed laser region 3, and the width of the end side 42 matching the width of the holding region 42. The transition region 41 tapers over a distance of 1000 μm to 1600 μm, i.e. the distance between the starting side 411 and the terminating side 412 is 1000 μm to 1600 μm. The holding region 42 has a length of 500 μm to 1000 μm and a width of 10 μm. Taking the width of the seed laser region 3 as 150 μm as an example, the bus waveguide 4 is tapered from 150 μm to 1000 μm to 1600 μm to form a waveguide structure with a width of 10 μm, and the transmission width of 10 μm is maintained to be 500 μm to 1000 μm. The specific structure of the bus waveguide 4 is shown in fig. 3, and includes a second active region 43 and a second top metal layer 44 from bottom to top. A portion of the second active region 43 and a portion of the second top metal layer 44 are in a trapezoid shape, short sides of the trapezoid portions jointly form the start side 411, and long sides jointly form the end side 412. In addition, a second top metal layer 44 is used for the leads to provide electrical pumping.

Referring again to fig. 1, the resonant ring 5 includes, in order from bottom to top, a third active region 51 and a third top metal layer 52. Wherein 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 which are equidistantly arranged and are circumferentially arranged at a certain angle, and each group of double slits is composed of two single slits with the length directions pointing to the axis of the resonance ring. The width of the single slit is between 2 and 6 μm, and the length is between 8 and 14 μm.

Since the radius r of the resonant ring 5 and its whispering gallery mode order N satisfy: k is a radical of₀×n_effX r is N, wherein k₀Is the wave vector in vacuum, n_effIs the effective refractive index. Thus, the whispering gallery mode order N of the resonant ring 5 can be adjusted by adjusting its radius r. In addition, the topological charge number of the target vector vortex optical rotation is related to the number M of the double slits, namely the decomposed topological charge numbers of the left-handed/right-handed circular polarization vortex optical rotation are respectively N-M + 1/N-M-1. In actual design, the distance between the resonant ring 5 and the bus waveguide 4 can be adjusted to improve the coupling efficiency, and the included angle theta between the two single slits of each group of double slits is designed to be one-fourth of the effective wavelength to suppress the reverse whispering gallery mode and improve the coupling efficiency and the mode purity of the vortex laser. Taking the excitation of 3 rd order/1 th order left/right hand circularly polarized vortex rotation as an example, the required parameters are as follows: r 170.1 μ M, N40, M38, θ 2.34 °. The seed laser 3 generates seed laser with fixed frequency, which is coupled into the resonant ring 5 through the bus waveguide 4, and excites the whispering gallery mode of the resonant ring 5. Because the radiation unit of the resonant ring 5 is composed of periodic double slits, and the number of the double slits and the whispering gallery mode order of the resonant ring have fixed difference, the emitted laser has fixed phase difference, which is beneficial to constructing the phase distribution of the vortex rotation.

The transition electrode 6 is located on the right side of the resonance loop 5 in fig. 1 (i.e. the side close to the seed laser 3) and comprises, from bottom to top, a fourth active region 61 and a fourth top metal layer 62 for providing electrical pumping to the resonance loop 5 via the metal-air bridge 7. The transition electrode 6 is a square with the side length of 100-400 μm, and the distance between the transition electrode and the resonant ring 5 is 5-70 μm.

The metal air bridge 7 is a raised metal structure with air below it for connecting the resonance ring 5 and the transition electrode 6. The length and width of the metal air bridges 7 are 5 μm to 70 μm and 4 μm to 30 μm, respectively. The absorption boundary 8 comprises a fifth active region for absorbing unwanted electromagnetic fields. It should be noted that the first active region 31, the second active region 43, the third active region 51, the fourth active region 61, and the fifth active region are the same active region (i.e., top surfaces of the first active region 31, the second active region 43, the third active region 51, the fourth active region 61, and the fifth active region are at the same height), and are prepared in one step, and 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 also the same metal layer (i.e., top surfaces and bottom surfaces 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, so that they are separated for convenience of description.

A method for manufacturing the terahertz vector vortex quantum cascade laser is described below.

As shown in fig. 4, the preparation method of the terahertz vector vortex quantum cascade laser provided by the invention comprises the following steps:

step S1, a substrate 1 having a bonding metal layer 2 and an active region layer is prepared. The method comprises the following steps:

step S11, preparing a first substrate having a first metal layer: the method comprises the steps of 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 forming a first metal layer on the lower contact layer. The active region layer comprises 90 modules with periodic repetition, each module comprises 9 GaAs potential wells and 9 Al layers overlapped with each other_0.15Ga_0.85As potential barrier, the thickness from GaAs is As follows: 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 and 2.7(nm), the GaAs layer of the first two layers is a doped layer, and the n-type doping concentration is 10¹⁶cm^-3。

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

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 above bonding metal layer 2.

In step S14, the first substrate is etched to expose the corrosion barrier layer, and the corrosion barrier layer is removed by an acid solution (e.g., HF acid or concentrated hydrochloric acid). At this time, the second base having the second metal layer remains to form the above-described substrate 1, and the substrate 1 having the bonding metal layer 2 and the active region layer is completed.

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

And step S3, manufacturing a periodic grating pattern on the surface of the active area layer in the absorption edge pattern area by adopting a photoetching technology, and corroding the active area layer with the periodic grating pattern by adopting a corrosive liquid of a sulfuric acid system to obtain a periodic grating slit. At this time, the active region having the periodic grating slit corresponds to the first active region 31. Wherein, the corrosion depth is calibrated by a step profiler. After the etching is completed, the photoresist on the surface of the active region layer needs to be removed.

And step S4, manufacturing an electrode pattern on the surface of the active area layer with the periodic grating slit by adopting a photoetching technology, growing metal on the photoetched electrode pattern by adopting an electron beam evaporation method, a magnetron sputtering method or a thermal evaporation method, and stripping the photoresist to form a top metal layer. The top metal layers at this time correspond 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. Wherein the third top metal layer 52 has a double slit pattern.

Step S5, using the photoresist as a mask of the top metal layer, etching the region of the active region layer not covered by the photoresist to expose the bonding metal layer. Note that the photoresist 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. And after etching is finished, removing the photoresist on the surface of the active area layer. At this time, the seed laser region 3, the bus waveguide 4, the resonance ring 5, the transition electrode 6, and the absorption boundary 8 are completed.

In step S6, a metal air bridge 7 is formed between the resonant ring 5 and the transition electrode 6. The process of making the metal air bridge 7 is shown in fig. 5 and comprises:

in step S61, a low-speed photoresist coating process is used to fill the photoresist into the gap between the resonant ring 5 and the transition electrode 6, 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.

In step S62, the photoresist is baked at a high temperature (140 ℃) for a period of time (e.g., 15 minutes) to deform and arch the photoresist on the surfaces of the third top metal layer 52 and the fourth top metal layer 62.

Step S63, forming a photoresist inverted mesa 71 by using an inverse photoresist process, and growing metal on the deformed and arched photoresist surface by using an electron beam evaporation method.

And step S64, performing top gluing protection on all the areas subjected to the step S63, thinning the substrate 1 subjected to the step S63 to about 200 microns through citric acid chemical corrosion, and growing metal on the back of the thinned substrate 1 to improve the heat dissipation performance. The chemical corrosion is chosen to avoid stressing the top air bridge metal.

Step S65, stripping the excess metal in acetone, and removing the filled photoresist with a photoresist stripper, to finally prepare the metal air bridge 7 as shown in fig. 5.

By using the invention, the terahertz scalar vortex laser with high mode purity can be obtained, and the performance of the laser is described in detail through experimental results.

FIG. 6 shows the L-I-V test results of the terahertz vector vortex quantum cascade laser at different temperatures, which are measured in a pulse mode with the repetition frequency of 60kHz and the pulse width of 1 mus. The laser and the resonant ring were pumped simultaneously during the test. As can be seen, the maximum output power of the device at 20K is 5.78mW, and the maximum output power at 77K is 3.78 mW.

Fig. 7 shows a spectral characteristic test result of the terahertz vector vortex quantum cascade laser of the present invention. The pumping conditions were: simultaneously, a laser and a resonant ring are pumped, and the repetition frequency is 60kHz, and the pulse width is 1 mu s. The test temperature was 77K. As can be seen from the figure, the laser maintains a single mode characteristic starting from the threshold current with increasing current until a multi-mode characteristic occurs at peak current. The center frequency of laser radiation is f 3.445 THz.

Fig. 8 shows the mode purity of the l/d circularly polarized vortex rotation of the vortex light emitted by the laser after separation. The topological charge numbers of the levorotatory/dextrorotatory circular polarization vortex rotation can be respectively 3 and 1. The results are in accordance with the theoretical design (40 scale whispering gallery modes and 38 scattering elements) with mode purities as high as 87.7% and 91%, respectively.

The invention can realize the hollow annular far-field light spot, the emitted vector vortex optical rotation can be decomposed into left-handed and right-handed circularly polarized light carrying orbital angular momentum, and the invention has the characteristics of high mode purity, narrow line width and high side mode suppression ratio.

The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.

Claims (10)

1. A terahertz vector vortex quantum cascade laser comprises a substrate and a bonding metal layer located above the substrate, and is characterized in that a seed laser area and a bus waveguide which are arranged along the length direction of the laser and are connected with each other, a resonant ring and a transition electrode which are arranged on one side of the bus waveguide, are arranged along the length direction of the laser and are separated from each other, a metal air bridge is erected between the resonant ring and the transition electrode, and absorption boundaries are arranged at the end part of the seed laser area and the end part of the bus waveguide.

2. The terahertz vector vortex quantum cascade laser of claim 1, wherein the seed laser region comprises, from bottom to top, a first active region and a first top metal layer, the first active region having a periodic grating structure therein.

3. The terahertz vector vortex quantum cascade laser of claim 2, wherein the periodic grating structure is composed of a plurality of elongated gratings of the same size, the elongated gratings being equally spaced.

4. The terahertz vector vortex quantum cascade laser of claim 1, wherein the bus waveguide comprises a transition region and a holding region, the transition region has a width that tapers from the seed laser region to the holding region, and the holding region is an elongated region with a constant width.

5. The terahertz vector vortex quantum cascade laser of claim 4, wherein the grading region has a starting side and an ending side, the starting side has a width that matches a width of the seed laser region, and the ending side has a width that matches a width of the holding region.

6. The terahertz vector vortex quantum cascade laser of claim 1, wherein the resonant ring comprises a third active region and a third top metal layer from bottom to top in sequence, and the third top metal electrode has a periodic double-slit structure.

7. The terahertz vector vortex quantum cascade laser of claim 6, wherein the periodic double-slit structure is composed of a plurality of groups of double slits arranged circumferentially at equal intervals and at a certain angle, and each group of double slits is composed of two single slits with length directions pointing to the axis of the resonance ring.

8. A preparation method of a terahertz vector vortex quantum cascade laser is characterized by comprising the following steps:

step S1, preparing a substrate with a bonding metal layer and an active area layer;

step S2, manufacturing an absorption edge pattern on a substrate with a bonding metal layer and an active area layer;

step S3, manufacturing a periodic grating pattern on the surface of the active area layer in the absorption edge pattern area, and corroding the active area 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, growing metal on the electrode pattern after photoetching, and forming a top metal layer after stripping;

step S5, taking the photoresist as the mask of the top metal layer, etching the area of the active area layer which is not covered by the photoresist to expose the bonding metal layer, and manufacturing and finishing the seed laser area, the bus waveguide, the resonance ring, the transition electrode and the absorption boundary;

step S6, a metal air bridge is fabricated between the resonance ring and the transition electrode.

9. The method for preparing the terahertz vector vortex quantum cascade laser as claimed in claim 8, wherein the step S1 comprises:

step S11, preparing a first substrate having a first metal layer; the method comprises the following steps: 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 forming a first metal layer on the lower contact layer;

step S12, preparing a second substrate having a second metal layer; the method comprises the following steps: providing a second substrate, and forming a second metal layer on the surface of the second substrate;

step S13, bonding the first metal layer and the second metal layer together to form a bonded metal layer;

and step S14, etching the first base to expose the corrosion barrier layer, and removing the corrosion barrier layer, wherein the second base is used as the substrate.

10. The method for preparing the terahertz vector vortex quantum cascade laser as claimed in claim 8, wherein the step S6 comprises:

step S61, filling photoresist into the gap between the resonant ring and the transition electrode, 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;

step S62, baking photoresist at high temperature to deform and arch the photoresist on the top metal layer of the resonance ring and the top metal layer of the transition electrode;

step S63, forming a photoresist inverted mesa, and growing metal on the deformed and arched photoresist surface;

step S64, performing top gluing protection on all the areas subjected to the step S63, thinning the substrate subjected to the step S63 through chemical corrosion, and growing metal on the back of the thinned substrate;

and step S65, stripping the redundant metal and removing the filled photoresist to prepare the metal air bridge.

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