Tunnel junction cascade coupling mode laser

Abstract

The invention provides a tunnel junction cascade coupling mode laser, which comprises an N-type structural layer, a first photonic crystal sub-layer, a main waveguide, a second photonic crystal sub-layer and a P-type structural layer which are sequentially stacked along a first direction, the main waveguide comprises two laser units which are superposed along a first direction, and a tunnel junction is arranged between any two laser units; the photonic crystal layer comprises a first photonic crystal sub-layer and a second photonic crystal sub-layer which are stacked on the two sides of the main waveguide in the first direction. The two overlapped laser units are mutually coupled to form a coupling optical cavity, and a coupling fundamental mode and a coupling high-order mode are lased in the coupling optical cavity; and the photonic crystal layer limits the coupling fundamental mode in the main waveguide and couples the coupling high-order mode into the photonic crystal layer to generate loss. According to the laser, the photonic crystal layer is arranged to dissipate a coupling high-order mode, coupling fundamental mode output is achieved, a far-field center main peak has a low divergence angle and high peak power density, and the output power of the laser is improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a tunnel junction cascade coupling mode laser. Background Art

[0002] Tunnel junction lasers are widely used in laser radar detection and other fields. In conventional tunnel junction lasers, a single laser epitaxial structure is usually used as a multi-active region series structure. The laser units are electrically connected to each other through a tunnel junction to form a waveguide that is isolated from each other. The thicker inner confinement layer of each unit completely confines the light field to its own waveguide region. The lasing modes of each unit are independent of each other and have no coherence. Its far field is a simple superposition of the far fields of each laser unit.

[0003] This conventional tunnel junction laser has the disadvantages that the laser units are spatially spaced in the epitaxial direction, the emission spots are separated from each other, and the peak positions of the far-field mode do not overlap, which greatly limits the utilization of the high output power of the tunnel junction laser. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings, the main purpose of the present invention is to provide a tunnel junction cascade coupled mode laser, which can achieve coupled fundamental mode output by arranging a photonic crystal layer to dissipate the coupled high-order modes. The far-field central main peak has a low divergence angle and a high peak power density, avoiding the complex optical path design for achieving fundamental mode coupling through an external cavity and improving the laser output power.

[0006] (II) Technical solution

[0007] In order to achieve the above-mentioned purpose, the present invention provides a tunnel junction cascade coupled mode laser, comprising: an N-type structure layer, a first photonic crystal sublayer, a main waveguide, a second photonic crystal sublayer and a P-type structure layer 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 a first photonic crystal sublayer and a second photonic crystal sublayer, and the first photonic crystal sublayer and the second photonic crystal sublayer are respectively arranged on both sides of the main waveguide along the first direction; in the main waveguide, 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 solution, the first photonic crystal sublayer and the second photonic crystal sublayer 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 lasing according to different selected bands, and the number of laser units in each band is set according to preset requirements, and photonic crystal layers with different structures are set accordingly to perform mode coupling in different bands.

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

[0011] In the above solution, the tunnel junction is a highly 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 optical field of the coupled high-order mode at the tunnel junction is less than 10 -2 , the relative intensity of the optical 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 sequence from bottom to top along a first direction; and the other laser unit includes an N-type waveguide layer, an active layer and a P-type waveguide layer stacked in sequence from bottom to top along the first direction.

[0014] In the above solution, 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 along the first direction, and the gain layer includes quantum wells, quantum wires and quantum dots.

[0015] In the above solution, the N-type structural 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 solution, the P-type structural layer includes: a P-type buffer layer, a P-type contact layer and a P-type electrode layer.

[0017] (III) Beneficial effects

[0018] The technical solution of the embodiment of the present invention has at least the following beneficial effects:

[0019] (1) The tunnel junction cascade coupled mode laser is composed of multiple laser units cascaded by tunnel junctions to form a coupled mode optical cavity in the epitaxial direction, and its eigenmode is a coupled first-order mode. The coupled first-order mode is coupled into the photonic crystal layer for dissipation, which promotes the coupled fundamental mode to be preferentially emitted, and finally realizes the coupled fundamental mode output, thereby increasing the laser output power.

[0020] (2) The tunnel junction cascade coupled mode laser forms a coupled mode optical cavity through mutual coupling between the laser units of the tunnel junction cascade, which only generates gain for a specific coupled mode, reduces the number of modes, improves the beam coherence, and narrows the output beam spectrum of the laser. In addition, the formation of a large coupled mode optical cavity expands the mode volume of the coupled fundamental mode, reducing the far-field central main peak divergence angle of the coupled mode.

[0021] (3) The relative intensity of the optical field of the coupled high-order mode at the tunnel junction of this tunnel junction cascade coupled mode laser is less than 10 -2 By designing the light field distribution, the node of the coupled high-order mode coincides with the position of the tunnel junction, avoiding the strong absorption of the light field by the highly doped tunnel junction. At the same time, the mode coupling between the laser units overcomes the disadvantage of the incoherence of the beams between the multiple active regions in the tunnel junction laser, and improves the output beam quality of the tunnel junction laser.

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

[0023] Figure 1 A schematic diagram of the structure of a tunnel junction cascade coupled mode laser according to an embodiment of the present invention is shown;

[0024] Figure 2 A schematic diagram of the structure of a photonic crystal sublayer according to an embodiment of the present invention is shown;

[0025] Figure 3 Schematically shows a refractive index distribution diagram according to an embodiment of the present invention;

[0026] Figure 4a Schematically showing the electric field distribution diagram of the fundamental mode according to an embodiment of the present invention;

[0027] Figure 4b Schematically shows an electric field distribution diagram of a first-order coupling mode according to an embodiment of the present invention;

[0028] Figure 4c Schematically shows an electric field distribution diagram of a second-order coupling mode according to an embodiment of the present invention;

[0029] 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. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

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

[0032] Please refer to Figure 1 An embodiment of the present invention provides a tunnel junction cascade coupled mode laser, comprising: an N-type structure layer 1, a first photonic crystal sublayer 31, a main waveguide 2, a second photonic crystal sublayer 32 and a P-type structure layer 4 stacked in sequence along a first direction X1, wherein; the main waveguide 2 comprises at least two laser units 21 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 a first photonic crystal sublayer 31 and a second photonic crystal sublayer 32, and the first photonic crystal sublayer 31 and the second photonic crystal sublayer 32 are respectively arranged on both sides of the main waveguide 2 along the first direction X1; in the main waveguide 2, at least two stacked laser units 21 are coupled to each other to form a coupled optical cavity, and coupled fundamental mode and coupled high-order mode are lasered 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.

[0033] Specifically, in the embodiment of the present invention, the first direction X1 is the epitaxial direction of the laser structure, such as Figure 1 As shown, two laser units 21 are stacked on each other along the first direction X1, for example, the two laser units 21 are laser units LU1 and LU2 respectively. The tunnel junction 5 provided 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 each other to form a coupled optical cavity, and the coupled fundamental mode and the coupled high-order mode are laser-coupled in the coupled optical cavity. Among them, the coupled high-order mode is a multi-waveguide structure that is coupled to each other to form a number of coupled modes equal to 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 includes at least two laser units 21 stacked along the first direction X1, and a tunnel junction 5 is provided between any two laser units 21. That is, more than two laser units 21 may be provided in the main waveguide 2, and any two adjacent stacked laser units 21 are connected through the tunnel junction 5 to be coupled together to form a coupled mode optical cavity.

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

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

[0037] Furthermore, the tunnel junction 5 is a highly doped PN junction having two layers, and the tunnel junction 5 is in a reverse bias state.

[0038] Exemplarily, the tunnel junction 5 is a double-layer reverse-biased PN junction, including: a P-type layer, made of GaAs, with a doping concentration greater than 10 19 cm -3 N-type layer, made of GaAs, with a doping concentration greater than 10 19 cm -3 , ensuring a larger tunneling peak current and smaller series resistance.

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

[0040] Specifically, if Figure 1 As shown, the laser unit LU1 includes a P-type waveguide layer 212, an active layer 213 and an N-type waveguide layer 214 stacked in sequence from bottom to top along the first direction X1; the laser unit LU2 includes an N-type waveguide layer 214, an active layer 213 and a P-type waveguide layer 212 stacked in sequence from bottom to top along the first direction X1.

[0041] It should be noted that if Figure 1 As shown, the laser unit LU1 further includes a P-type confinement layer 215 which may be provided 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 which may be provided 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 which may be provided 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 which may be provided on a side of the N-type waveguide layer 214 away from the active layer 213 along the first direction X1.

[0042] In an embodiment of the present invention, the active layer 213 in any laser unit 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 quantum wells, quantum wires and quantum dots, and adopts different materials and structures according to the specific band.

[0043] Exemplarily, the active layers 213 of the two laser units, namely the laser unit LU1 and the laser unit LU2, have gain layers of InGaAs quantum wells, and potential well layers on both sides of the active layers are AlGaAs alloys with graded composition, and the peak wavelength of the gain spectrum is around 905 nm.

[0044] Please continue reading Figure 1 A first photonic crystal sublayer 31 and a second photonic crystal sublayer 32 are respectively disposed on both sides of the main waveguide 2 along the first direction X1. The photonic crystal layer 3 includes the first photonic crystal sublayer 31 and the second photonic crystal sublayer 32.

[0045] In the embodiment of the present invention, the photonic crystal structure is an artificial periodic dielectric structure with photonic bandgap characteristics, sometimes also called a PBC photonic crystal structure. This structure itself has "allowed bands" and "forbidden bands" for light waves of different frequencies.

[0046] Exemplarily, the first photonic crystal sublayer 31 may be located on a side close to the N-type structure layer 1 , and the second photonic crystal sublayer 32 may be located on a side close to the P-type structure layer 4 .

[0047] It should be noted that, in the embodiment of the present invention, the first photonic crystal sublayer 31 and the second photonic crystal sublayer 32 may also be stacked on one side of the main waveguide 2 along the first direction X1.

[0048] Based on the above tunnel junction cascade coupling mode laser, it includes a main waveguide and photonic crystal layers selectively arranged on both sides of the main waveguide; wherein the main waveguide is composed of at least two superimposed laser units stacked to form a large optical cavity structure of a coupled fundamental mode, the inner confinement layer of the laser unit is thinned or even removed to promote the expansion of each laser unit mode to the adjacent laser unit waveguide for strong coupling, a tunnel junction is arranged between adjacent laser units, and photonic crystal layers can be selectively arranged on both sides of the main waveguide to regulate the coupling mode, the photonic crystal layer can adjust the logarithm and structure according to the coupling mode requirements, and the photonic crystal layer can be simplified according to the process conditions.

[0049] In the embodiment of the present invention, the photonic crystal layer 3 confines the coupled fundamental mode within the main waveguide 2 and couples the coupled high-order mode into the photonic crystal layer 3 to generate loss.

[0050] Figure 2 A schematic structural diagram of a photonic crystal sublayer according to an embodiment of the present invention is shown. Figure 3 The refractive index distribution diagram according to an embodiment of the present invention is schematically shown.

[0051] like Figure 2 As 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] Exemplarily, any photonic crystal sub-layer may 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 invention, by coupling the coupled high-order mode into the first photonic crystal sublayer 31 and the second photonic crystal sublayer 32, the optical confinement factor of the coupled high-order mode in the gain region is reduced, thereby promoting the lasing of the coupled fundamental mode.

[0054] Furthermore, in the main waveguide 2, any two laser units 21 can lasing according to different selected bands, and the number of laser units 21 in each band can be set according to preset requirements, and photonic crystal layers 3 with different structures can be set accordingly to perform mode coupling in different bands.

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

[0056] Figure 4a-4c yes Figure 3 The electric field distribution diagram of different coupling modes in the embodiment of the present invention is shown in FIG. In the embodiment, the relative intensity of the optical field of the coupled high-order mode at the tunnel junction 5 is less than 10 -2 , the relative intensity of the optical field of the coupled fundamental mode at the tunnel junction 5 is greater than 10 -1 .

[0057] Specifically, since the tunnel junction 5 connected to the laser unit usually has a high doping concentration and high light absorption, the relative intensity of the light field in the tunnel junction 5 area is less than 10 -2 The coupled high-order mode is preferentially lased, but the electric fields of the coupled high-order mode on both sides of the node are inversely phased, and the far-field distribution is a separated multi-lobe light spot, which is not conducive to the use of the laser beam. Therefore, in this embodiment, the coupled high-order mode is coupled and dissipated by setting the photonic crystal layer 3, so that the coupled fundamental mode is lased, and finally the coupled fundamental mode output is achieved.

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

[0059] Please continue reading Figure 1 The N-type structure layer 1 of the tunnel junction cascade coupled mode laser includes 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 from bottom to top along the first direction X1.

[0060] like Figure 1 As shown, specifically, the N-type electrode layer 11 is constructed to provide a channel for electrical injection for 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 structural 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 finally 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 of the tunnel junction cascade in the epitaxial direction to form a coupled mode optical cavity, and the mode distribution is regulated by introducing photonic crystal layers on both sides, and finally coupled fundamental mode output can be achieved. That is, by setting the photonic crystal layer to dissipate the coupled high-order mode, coupled fundamental mode output can be achieved, and the central main peak of the far field has a low divergence angle and high peak power density, avoiding the complex optical path design of realizing fundamental mode coupling through the external cavity, so that the laser has broad application prospects in the fields of laser ranging, laser radar, etc.

[0066] The above specific embodiments further illustrate the purpose, 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 protection scope of the present invention.

Claims

1. A tunnel junction cascade coupled mode laser, characterized in that: include: An N-type structural layer (1), a first photonic crystal sublayer (31), a main waveguide (2), a second photonic crystal sublayer (32), and a P-type structural layer (4) are sequentially stacked along a first direction, wherein; The main waveguide (2) comprises at least two laser units (21) stacked along a first direction, and a tunnel junction (5) is provided between any two of the laser units (21); The photonic crystal layer (3) comprises the first photonic crystal sublayer (31) and the second photonic crystal sublayer (32), wherein the first photonic crystal sublayer (31) and the second photonic crystal sublayer (32) are respectively arranged on both sides of the main waveguide (2) along a first direction; In the main waveguide (2), the at least two stacked laser units (21) are coupled to each other to form a coupled optical cavity, and a coupled fundamental mode and a coupled high-order mode are laser-induced in the coupled optical cavity; and The photonic crystal layer (3) confines the coupled fundamental mode within 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 according to claim 1, characterized in that: The first photonic crystal sublayer (31) and the second photonic crystal sublayer (32) are both stacked on one side of the main waveguide (2) along a first direction.

3. The tunnel junction cascade coupled mode laser according to claim 1, characterized in that: In the main waveguide (2), any two laser units (21) can perform lasing according to different selected wavelength bands, and The number of laser units (21) in each wavelength band is set according to preset requirements, and photonic crystal layers (3) with different structures are correspondingly set to perform mode coupling in different wavelength bands.

4. The tunnel junction cascade coupled mode laser according to claim 1 or 3, characterized in that: 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 according to claim 1, characterized in that: The tunnel junction (5) is a highly 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 according to claim 1 or 5, characterized in that: The relative intensity of the optical field of the coupled high-order mode at the tunnel junction (5) is less than 10 -2 , the relative intensity of the optical field of the coupling fundamental mode at the tunnel junction (5) is greater than 10 -1 .

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

8. The tunnel junction cascade coupled mode laser according to claim 7, characterized in that: The active layer (213) in any 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 a quantum well, a quantum wire and a quantum dot.

9. The tunnel junction cascade coupled mode laser according to claim 1, characterized in that: The N-type structural 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 according to claim 1, characterized in that: The P-type structural 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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