A tunnel junction cascade coupled mode laser

Abstract

The application provides a tunnel junction cascade coupling mode laser, which comprises N-type structure layers, first photonic crystal sub-layers, main waveguides, second photonic crystal sub-layers and P-type structure layers which are sequentially stacked in a first direction; the main waveguide comprises two laser units which are stacked in the first direction, and a tunnel junction is arranged between the two laser units; the photonic crystal layer comprises the first photonic crystal sub-layers and the second photonic crystal sub-layers which are stacked on both sides of the main waveguide in the first direction; the two stacked laser units are coupled with each other to form a coupled optical cavity, and a coupled basic mode and a coupled high-order mode are generated in the coupled optical cavity; and the photonic crystal layer limits the coupled basic mode in the main waveguide and couples the coupled high-order mode into the photonic crystal layer to generate loss. The laser dissipates the coupled high-order mode through the photonic crystal layer, realizes the output of the coupled basic mode, and the central main peak of the far field has a low divergence angle and a high peak power density, so that the output power of the laser is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor optoelectronic devices, in particular to a tunnel junction cascaded coupling mode laser. BACKGROUND

[0002] Tunnel junction lasers are widely used in the field of laser radar detection. In a conventional tunnel junction laser, a single laser epitaxial structure is usually taken as a multi-active region series structure, the laser units are isolated from each other by a tunnel junction to form a waveguide, and a relatively thick inner confinement layer of each unit completely confines the optical field in the waveguide region, so that the lasing modes of each unit are independent of each other and have no coherence, and the far field is a simple superposition of the far fields of each laser unit.

[0003] The conventional tunnel junction laser has the disadvantages that the laser units are spaced apart in the epitaxial direction, the exit light spots are separated from each other, and the peak positions of the far field modes do not coincide, which greatly limits the use of high output power of the tunnel junction laser. SUMMARY

[0004] (I) Technical problem to be solved

[0005] In view of the above problems, the main purpose of the present application is to provide a tunnel junction cascaded coupling mode laser, which can realize coupling of the fundamental mode by setting a photonic crystal layer to dissipate the coupled high-order modes, has a low divergence angle and a high peak power density in the center of the far field, avoids the complex optical path design for realizing the coupling of the fundamental mode by an external cavity, and improves the output power of the laser.

[0006] (II) Technical scheme

[0007] In order to achieve the above purpose, the present application provides a tunnel junction cascaded coupling mode laser, comprising: N-type structure layer, first photonic crystal sub-layer, main waveguide, second photonic crystal sub-layer and P-type structure layer which are stacked in sequence along a first direction, wherein: the main waveguide comprises at least two laser units stacked along the first direction, and a tunnel junction is arranged between any two laser units; the photonic crystal layer comprises the first photonic crystal sub-layer and the second photonic crystal sub-layer, and the first photonic crystal sub-layer and the second photonic crystal sub-layer are arranged on both sides of the main waveguide along the first direction; in the main waveguide, the at least two stacked laser units are coupled to each other to form a coupled optical cavity, and a coupled fundamental mode and a coupled high-order mode are lased in the coupled optical cavity; and the photonic crystal layer confines the coupled fundamental mode in the main waveguide and couples the coupled high-order mode into the photonic crystal layer to generate loss.

[0008] In the above scheme, the first photonic crystal sub-layer and the second photonic crystal sub-layer are both stacked on one side of the main waveguide along the first direction.

[0009] In the above scheme, in the main waveguide, any two laser units can lase according to different wave bands, and the number of laser units of each wave band is set according to the preset requirement, and the photonic crystal layer of different structures is set to divide the wave band and perform mode coupling.

[0010] In the above scheme, the waveguide structure of each laser unit in the main waveguide is a large optical cavity structure.

[0011] In the above scheme, the tunnel junction is a high-doped PN junction with two layers, and the tunnel junction is in a reverse bias state.

[0012] In the above scheme, the relative intensity of the light field of the coupled high-order mode at the tunnel junction is less than 10 -2 , and the relative intensity of the light field of the coupled fundamental mode at the tunnel junction is greater than 10 -1 .

[0013] In the above scheme, one of any two laser units includes a P-type waveguide layer, an active layer, and an N-type waveguide layer stacked in the first direction from bottom to top in sequence; and the other laser unit includes an N-type waveguide layer, an active layer, and a P-type waveguide layer stacked in the first direction from bottom to top in sequence.

[0014] In the above scheme, the active layer in any laser unit includes a potential well layer and a gain layer, wherein the potential well layer is arranged on both sides of the gain layer in the first direction, and the gain layer includes quantum wells, quantum wires, and quantum dots.

[0015] In the above scheme, the N-type structure layer includes an N-type electrode layer, an N-type substrate layer, an N-type transition layer, and an N-type buffer layer.

[0016] In the above scheme, the P-type structure layer includes a P-type buffer layer, a P-type contact layer, and a P-type electrode layer.

[0017] (Three) beneficial effects

[0018] The technical scheme of the embodiment of the application has at least the following beneficial effects:

[0019] (1) The tunnel junction cascade coupling mode laser is formed by a plurality of laser units in the epitaxial direction, and the intrinsic mode is a coupled first-order mode. The coupled first-order mode is coupled into the photonic crystal layer to dissipate, which promotes the coupled fundamental mode to preferentially lase, and finally realizes the output of the coupled fundamental mode, thereby improving the output power of the laser.

[0020] (2) The tunnel junction cascade coupled mode laser forms a coupled mode optical cavity through mutual coupling between the tunnel junction cascade laser units, only produces gain for specific coupled modes, reduces the mode number, improves the beam coherence, and narrows the output beam spectrum of the laser. And the formation of the coupled mode large cavity expands the mode volume of the coupled mode, so that the central main peak divergence angle of the far field of the coupled mode is reduced.

[0021] (3) The tunnel junction cascade coupled mode laser, the relative intensity of the coupled high-order mode light field at the tunnel junction is less than 10 -2 By designing the light field distribution, the nodes of the coupled high-order mode coincide with the position of the tunnel junction, avoiding the strong absorption of the high-doped tunnel junction to the light field. At the same time, the mode coupling between the laser units overcomes the beam incoherence between multiple active regions in the tunnel junction laser, improving the output beam quality of the tunnel junction laser.

[0022] (4) By setting the photonic crystal layer to dissipate the coupled high-order mode, the coupled fundamental mode output can be realized, the far field central main peak has low divergence angle and high peak power density, avoiding the complex optical path design of realizing the fundamental mode coupling through an external cavity. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The structure schematic diagram of the tunnel junction cascade coupled mode laser according to the embodiment of the present application is shown;

[0024] Figure 2 The structure schematic diagram of the photonic crystal sublayer according to the embodiment of the present application is shown;

[0025] Figure 3 The refractive index distribution diagram according to the embodiment of the present application is shown schematically;

[0026] Figure 4a The electric field distribution diagram of the fundamental mode according to the embodiment of the present application is shown schematically;

[0027] Figure 4b The electric field distribution diagram of the first-order coupled mode according to the embodiment of the present application is shown schematically;

[0028] Figure 4c The electric field distribution diagram of the second-order coupled mode according to the embodiment of the present application is shown schematically;

[0029] Figure 5 The vertical far field distribution diagram of the tunnel junction cascade coupled mode laser according to the embodiment of the present application is shown schematically. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below, combined with specific embodiments and referring to the drawings.

[0031] Figure 1 A structural schematic diagram of a tunnel junction cascade coupling mode laser according to an embodiment of the present application is shown.

[0032] For details, please refer to Figure 1 The embodiment of the present application provides a tunnel junction cascade coupling mode laser, which comprises N-type structure layer 1, first photonic crystal sub-layer 31, main waveguide 2, second photonic crystal sub-layer 32 and P-type structure layer 4 which are sequentially stacked along a first direction X1, wherein the main waveguide 2 comprises at least two laser units 21 which are stacked along the first direction X1, and a tunnel junction 5 is arranged between any two laser units 21; the photonic crystal layer 3 comprises the first photonic crystal sub-layer 31 and the second photonic crystal sub-layer 32 which are arranged on both sides of the main waveguide 2 along the first direction X1; in the main waveguide 2, the at least two stacked laser units 21 are coupled to form a coupled optical cavity, and a coupled fundamental mode and a coupled high-order mode are oscillated in the coupled optical cavity; and the photonic crystal layer 3 limits the coupled fundamental mode in the main waveguide 2 and couples the coupled high-order mode into the photonic crystal layer 3 to generate loss.

[0033] Specifically, in the embodiment of the present application, the first direction X1 is the epitaxial direction of the laser structure, as Figure 1 shown, two laser units 21 which are stacked along the first direction X1, for example, the two laser units 21 are laser units LU1 and LU2 respectively. The tunnel junction 5 arranged between the two laser units 21 together constitutes the main waveguide 2. In the main waveguide 2, the waveguide layers of the two laser units 21 are coupled to form a coupled optical cavity, and a coupled fundamental mode and a coupled high-order mode are oscillated in the coupled optical cavity. Among them, the coupled high-order mode is that the multiple waveguide structures are coupled to form the same number of coupled modes as the number of coupled waveguides, and the mode with an order greater than zero is a high-order mode.

[0034] It should be noted that the main waveguide 2 comprises at least two laser units 21 which are stacked along the first direction X1, and a tunnel junction 5 is arranged between any two laser units 21. That is, more than two laser units 21 can be arranged in the main waveguide 2, and any two adjacent stacked laser units 21 are connected by the tunnel junction 5 to form a coupled mode optical cavity.

[0035] In the embodiment of the present application, the waveguide structure of each laser unit 21 in the main waveguide 2 is a large optical cavity structure.

[0036] Further, in the main waveguide 2, any two laser units 21 can oscillate according to different wave bands, and the number of laser units 21 of each wave band can also be set according to the preset requirements.

[0037] Further, the tunnel junction 5 is a high-doped PN junction with two layers, and the tunnel junction 5 is in a reverse bias state.

[0038] For example, the tunnel junction 5 is a double-layer reverse-biased PN junction, which includes a P-type layer made of GaAs and having a doping concentration greater than 10 19 cm -3 , and an N-type layer made of GaAs and having a doping concentration greater than 10 19 cm -3 , so as to ensure a large tunneling peak current and a small series resistance.

[0039] In the embodiment of the present application, one of the two laser units 21 includes, in sequence from bottom to top along the first direction X1, a P-type waveguide layer 212, an active layer 213, and an N-type waveguide layer 214; and the other laser unit 21 includes, in sequence from bottom to top along the first direction X1, an N-type waveguide layer 214, an active layer 213, and a P-type waveguide layer 212.

[0040] Specifically, as shown in FIG. 1, the laser unit LU1 includes, in sequence from bottom to top along the first direction X1, a P-type waveguide layer 212, an active layer 213, and an N-type waveguide layer 214; and the laser unit LU2 includes, in sequence from bottom to top along the first direction X1, an N-type waveguide layer 214, an active layer 213, and a P-type waveguide layer 212. Figure 1 It should be noted that, as shown in FIG. 1, the laser unit LU1 further includes a P-type confinement layer 215 arranged on a side of the P-type waveguide layer 212 away from the active layer 213 along the first direction X1, and an N-type confinement layer 216 arranged on a side of the N-type waveguide layer 214 away from the active layer 213 along the first direction X1. The laser unit LU2 further includes a P-type confinement layer 215 arranged on a side of the P-type waveguide layer 212 away from the active layer 213 along the first direction X1, and an N-type confinement layer 216 arranged on a side of the N-type waveguide layer 214 away from the active layer 213 along the first direction X1.

[0041] Figure 1 In the embodiment of the present application, the active layer 213 in any of the laser units 21 includes a potential well layer and a gain layer, wherein the potential well layer is arranged on both sides of the gain layer along the first direction X1, and the gain layer includes a quantum well, a quantum wire, and a quantum dot, and different materials and structures are adopted according to specific wave bands.

[0042] For example, the active layer 213 of the two laser units, the laser unit LU1 and the laser unit LU2, has an InGaAs quantum well as the gain layer, and AlGaAs alloy with gradually changing components as the potential well layer on both sides, and the peak wavelength of the gain spectrum is near 905 nm.

[0043] For example, the active layer 213 of the two laser units, the laser unit LU1 and the laser unit LU2, has an InGaAs quantum well as the gain layer, and AlGaAs alloy with gradually changing components as the potential well layer on both sides, and the peak wavelength of the gain spectrum is near 905 nm. ​

[0044] Please continue to refer to Figure 1 The first photonic crystal sub-layer 31 and the second photonic crystal sub-layer 32 are respectively arranged on the two sides of the main waveguide 2 along the first direction X1. The photonic crystal layer 3 includes the first photonic crystal sub-layer 31 and the second photonic crystal sub-layer 32.

[0045] In the embodiment of the present application, the photonic crystal structure is a periodic artificial dielectric structure with photonic band gap characteristics, which is also called PBC photonic crystal structure. The structure itself has a "passband" and a "forbidden band" for different frequency light waves.

[0046] For example, the first photonic crystal sub-layer 31 can be arranged on the side close to the N-type structure layer 1, and the second photonic crystal sub-layer 32 can be arranged on the side close to the P-type structure layer 4.

[0047] It should be noted that in the embodiment of the present application, the first photonic crystal sub-layer 31 and the second photonic crystal sub-layer 32 can also be arranged on one side of the main waveguide 2 along the first direction X1.

[0048] Based on the above-mentioned tunnel junction cascade coupling mode laser, the laser includes a main waveguide and a photonic crystal layer selectively arranged on the two sides of the main waveguide; wherein the main waveguide is composed of at least two superimposed laser units to form a large optical cavity structure of a coupling mode, the inner confinement layer of the laser unit is thinned or even removed to promote the mode expansion of each laser unit to the adjacent laser unit waveguide to occur strong coupling, a tunnel junction is arranged between the adjacent laser units, and a photonic crystal layer can be selectively arranged on the two sides of the main waveguide to regulate the coupling mode. The photonic crystal layer can adjust the number and structure according to the coupling mode requirement, and the photonic crystal layer can be simplified according to the process condition.

[0049] In the embodiment of the present application, the photonic crystal layer 3 limits the coupling mode in the main waveguide 2, and couples the coupling high-order mode into the photonic crystal layer 3 to generate loss.

[0050] Figure 2 A structure diagram of the photonic crystal sub-layer according to the embodiment of the present application is shown. Figure 3 A refractive index distribution diagram according to the embodiment of the present application is schematically shown.

[0051] As Figure 2 shown, any photonic crystal sub-layer includes a high refractive index layer 311 and a low refractive index layer 312, wherein the high refractive index layer 311 and the low refractive index layer 312 are arranged alternately.

[0052] For example, any photonic crystal sub-layer can include a plurality of pairs of high refractive index layers 311 and low refractive index layers 312.

[0053] According to Figure 3As shown, in the embodiment of the present application, by coupling the high-order modes into the first photonic crystal sub-layer 31 and the second photonic crystal sub-layer 32, the light confinement factor of the high-order modes in the gain region is reduced, which promotes the lasing of the base mode.

[0054] Further, in the main waveguide 2, any two laser units 21 can lase according to different wavelength bands, and the number of laser units 21 of each wavelength band can be set according to the preset requirement, and the photonic crystal layer 3 of different structures can be set to perform mode coupling in different wavelength bands.

[0055] Figure 4a The electric field distribution of the base mode according to the embodiment of the present application is schematically shown. Figure 4b The electric field distribution of the first-order coupling mode according to the embodiment of the present application is schematically shown. Figure 4c The electric field distribution of the second-order coupling mode according to the embodiment of the present application is schematically shown.

[0056] Figures 4a-4c is Figure 3 The electric field distribution of different coupling modes in the embodiment of the present application is shown. In the embodiment, the relative light field intensity of the high-order coupling mode at the tunnel junction 5 is less than 10 -2 , and the relative light field intensity of the base mode at the tunnel junction 5 is greater than 10 -1 .

[0057] Specifically, since the tunnel junction 5 connecting the laser units usually has a very high doping concentration and a very high light absorption, the high-order coupling mode with the relative light field intensity less than 10 -2 at the tunnel junction 5 region preferentially lases, but the electric field on both sides of the node of the high-order coupling mode is opposite to each other, and the far field distribution is a separated multi-lobe spot, which is not conducive to the utilization of the laser beam. Therefore, in the embodiment, the photonic crystal layer 3 is arranged to couple and dissipate the high-order coupling mode, so that the base mode lases and finally outputs.

[0058] The tunnel junction cascade coupling mode laser, the relative light field intensity of the high-order coupling mode at the tunnel junction is less than 10 -2 , that is, by designing the light field distribution, the node of the high-order coupling mode coincides with the position of the tunnel junction, which avoids the strong absorption of the high-doped tunnel junction to the light field. At the same time, the laser units are coupled by the mode, which overcomes the disadvantage that the light beams between the multiple active regions in the tunnel junction laser are incoherent, and improves the output beam quality of the tunnel junction laser.

[0059] Please continue to refer to Figure 1 The N-type structure layer 1 of the tunnel junction cascade coupling mode laser includes, from bottom to top along the first direction X1, an N-type electrode layer 11, an N-type substrate layer 12, an N-type transition layer 13, and an N-type buffer layer 14.

[0060] like Figure 1 As shown, specifically, the N-type electrode layer 11 is constructed to provide a channel for electrical injection into the laser device; the N-type substrate layer 12 is arranged on the N-type electrode layer 11 to support the semiconductor chip; the N-type transition layer 13 is constructed to perform composition and doping transition between the N-type substrate layer 12 and the N-side photonic crystal layer.

[0061] Please continue reading Figure 1 The P-type structure layer 4 includes a P-type buffer layer 41 , a P-type contact layer 42 and a P-type electrode layer 43 .

[0062] Specifically, along the first direction X1, the P-type buffer layer 41 is arranged on the second photonic crystal sublayer 32; the P-type contact layer 42 is arranged between the P-type buffer layer 41 and the P-type electrode layer 43; the P-type electrode layer 43 is arranged on the P-type contact layer 42, and is constructed to provide a channel for electrical injection for the laser device.

[0063] Figure 5 The vertical far-field distribution diagram of the tunnel junction cascade coupled mode laser according to an embodiment of the present invention is schematically shown.

[0064] according to Figure 5 It can be seen that the embodiment of the present invention couples the coupled high-order mode into the photonic crystal layer, thereby regulating the coupled mode distribution, and ultimately achieving laser output dominated by the coupled fundamental mode; by using a large optical cavity structure, the vertical far-field divergence angle of the tunnel junction cascade coupled mode laser is reduced, and the beam quality of the semiconductor laser is improved.

[0065] Through the embodiments of the present invention, the tunnel junction cascade coupled-mode laser is formed by coupling adjacent laser units in the epitaxial direction of the tunnel junction cascade to form a coupled-mode optical cavity. By introducing photonic crystal layers on both sides to regulate the mode distribution, it is ultimately possible to achieve coupled fundamental mode output. Specifically, by providing photonic crystal layers to dissipate the coupled higher-order modes, coupled fundamental mode output is achieved. The far-field central main peak has a low divergence angle and high peak power density, avoiding the complex optical path design required to achieve fundamental mode coupling through an external cavity. This makes the laser have broad application prospects in fields such as laser ranging and lidar.

[0066] The above specific embodiments further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A tunnel junction cascade coupled mode laser, comprising: The application relates to a laser device, comprising: N-type structure layer (1), first photonic crystal sub-layer (31), main waveguide (2), second photonic crystal sub-layer (32) and P-type structure layer (4) which are sequentially stacked along a first direction, wherein: The main waveguide (2) comprises at least two laser units (21) stacked along the first direction, and a tunnel junction (5) is arranged between any two laser units (21). The photonic crystal layer (3) comprises the first photonic crystal sub-layer (31) and the second photonic crystal sub-layer (32), and the first photonic crystal sub-layer (31) and the second photonic crystal sub-layer (32) are arranged on both sides of the main waveguide (2) along the first direction. In the main waveguide (2), the at least two stacked laser units (21) are coupled to form a coupled optical cavity, and a coupled fundamental mode and a coupled high-order mode are oscillated in the coupled optical cavity; and The photonic crystal layer (3) confines the coupled fundamental mode in the main waveguide (2) and couples the coupled high-order mode into the photonic crystal layer (3) to generate loss.

2. The tunnel junction cascade coupled mode laser of claim 1, wherein, The first photonic crystal sub-layer (31) and the second photonic crystal sub-layer (32) are both stacked on one side of the main waveguide (2) along the first direction.

3. The tunnel junction cascade coupled mode laser of claim 1, wherein, In the main waveguide (2), any two laser units (21) can oscillate at different wave bands according to selection, and The number of laser units (21) of each wave band is set according to a preset requirement, and a photonic crystal layer (3) with different structures is correspondingly arranged to perform mode coupling in a wave band.

4. The tunnel junction cascade coupled mode laser of claim 1 or 3, wherein, The waveguide structure of each laser unit (21) in the main waveguide (2) is a large optical cavity structure.

5. The tunnel junction cascade coupled mode laser of claim 1, wherein, The tunnel junction (5) is a high-doped PN junction with two layers, and the tunnel junction (5) is in a reverse bias state.

6. The tunnel junction cascade coupled mode laser of claim 1 or 5, wherein, the relative intensity of the optical field at the tunnel junction (5) of the coupled high order mode is less than 10 -2 , the relative intensity of the optical field at the tunnel junction (5) of the coupled fundamental mode is greater than 10 -1 .

7. The tunnel junction cascade coupled mode laser of claim 1, wherein, One of the any two laser units (21) comprises a P-type waveguide layer (212), an active layer (213) and an N-type waveguide layer (214) which are sequentially stacked along the first direction from bottom to top; and The other laser unit (21) comprises an N-type waveguide layer (214), an active layer (213) and a P-type waveguide layer (212) which are sequentially stacked along the first direction from bottom to top.

8. The tunnel junction cascade coupled mode laser of claim 7, wherein, The active layer (213) in any one of the laser units (21) comprises a potential well layer and a gain layer, wherein the potential well layer is arranged on both sides of the gain layer along the first direction, and the gain layer comprises quantum wells, quantum wires and quantum dots.

9. The tunnel junction cascade coupled mode laser of claim 1, wherein, The N-type structure layer (1) comprises an N-type electrode layer (11), an N-type substrate layer (12), an N-type transition layer (13) and an N-type buffer layer (14).

10. The tunnel junction cascade coupled mode laser of claim 1, wherein, The P-type structure layer (4) comprises a P-type buffer layer (41), a P-type contact layer (42) and a P-type electrode layer (43).

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