SEMICONDUCTOR LASER ELEMENT

• US 20160020581A1
• Filed: 02/27/2014
• Published: 01/21/2016
• Est. Priority Date: 03/04/2013
• Status: Active Grant

• Current Assignee: Hamamatsu Photonics KK, Kyoto University
• Original Assignee: Hamamatsu Photonics KK, Kyoto University
• Inventors: HIROSE, Kazuyoshi, WATANABE, Akiyoshi, KUROSAKA, Yoshitaka, SUGIYAMA, Takahiro, NODA, Susumu
• Granted Patent: US 9,583,914 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01S 2301/14 Semiconductor lasers with special structural design for lasing in a specific polarisation mode
• CPC Class Codes: H01S 3/08009 using a diffraction grating
• CPC Class Codes: H01S 5/04254 characterised by the shape
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/1231 Grating growth or overgrowth details
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H01S 5/18319 comprising a periodical structure in lateral directions
• CPC Class Codes: H01S 5/185 having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL] comprising a photonic bandgap structure H01S5/11
• CPC Class Codes: H01S 5/187 using Bragg reflection

Abstract

A semiconductor laser element is realized with high beam quality (index M²<1). A diffraction grating 6ba of a diffraction grating layer 6 extends along a principal surface 2a and is provided on a p-side surface 6a of the diffraction grating layer 6; the refractive index of the diffraction grating layer 6 periodically varies in directions extending along the principal surface 2a, in the diffraction grating 6ba; the diffraction grating 6ba has a plurality of holes 6b; the plurality of holes 6b are provided in the p-side surface 6a and arranged in translational symmetry along a square lattice R3; the plurality of holes 6b each have the same size and shape; each hole 6b corresponds to a lattice point of the diffraction grating 6ba and is of a triangular prism shape; a shape of a bottom face 6c of the hole 6b is an approximate right triangle.

Claims

1. A semiconductor laser element comprising a semiconductor laminate,

wherein the semiconductor laminate comprises

a support substrate, a first cladding layer, an active layer, a diffraction grating layer, and a second cladding layer,

wherein the first cladding layer, the active layer, the diffraction grating layer, and the second cladding layer are provided on a principal surface of the support substrate,

wherein the active layer and the diffraction grating layer are provided between the first cladding layer and the second cladding layer,

wherein the active layer generates light,

wherein the second cladding layer has a conductivity type different from a conductivity type of the first cladding layer,

wherein the diffraction grating layer has a diffraction grating,

wherein the diffraction grating has a two-dimensional photonic crystal structure of square lattice arrangement,

wherein the two-dimensional photonic crystal structure has a plurality of holes and extends along the principal surface,

wherein the plurality of holes have an identical shape and are arranged along a square lattice of the diffraction grating,

wherein the hole corresponds to a lattice point of the diffraction grating,

wherein a shape of a bottom face of the hole is an approximate right triangle,

wherein the hole has a refractive index different from a refractive index of a base material of the diffraction grating,

wherein a node of an electromagnetic field generated in the diffraction grating by luminescence of the active layer is located substantially at the same position as a centroid of the approximate right triangle of the hole, and

wherein an extremum of intensity of a magnetic field in the electromagnetic field is present around the hole.

2. The semiconductor laser element according to claim 1,

wherein the semiconductor laminate further comprises an electron blocking layer, and

wherein the electron blocking layer lies between a layer with a conductivity type of p-type in the first cladding layer and the second cladding layer, and the active layer.

3. The semiconductor laser element according to claim 1,

wherein the diffraction grating layer lies between a layer with a conductivity type of p-type in the first cladding layer and the second cladding layer, and the active layer.

4. The semiconductor laser element according to claim 1,

wherein a material of the semiconductor laminate is a III-V semiconductor containing GaAs.

5. The semiconductor laser element according to claim 1,

wherein the bottom face has a first side and a second side,

wherein the first side and the second side make a right angle, and

wherein the first side is inclined relative to a lattice vector of a square lattice.

6. The semiconductor laser element according to claim 1,

wherein each of three vertices of the approximate right triangle of the bottom face is rounded so as to overlap a circumference of a reference circle touching the sides internally at the vertex.

7. The semiconductor laser element according to claim 1,

wherein the approximate right triangle of the bottom face has a first side and a second side,

wherein the first side and the second side make a right angle,

wherein each of three vertices of the approximate right triangle of the bottom face is rounded so as to overlap a circumference of a reference circle touching the sides internally at the vertex,

wherein the shape of the approximate right triangle of the hole satisfies any one of the following conditions (1) to (10):

(1) a roundedness is 0.00×

a lattice constant, a filling factor is not less than 10% and not more than 25%, and an aspect ratio is not less than 1.00 and not more than 1.16;

(2) a roundedness is 0.00×

a lattice constant, a filling factor is not less than 15% and not more than 25%, and an aspect ratio is not less than 1.16 and not more than 1.20;

(3) a roundedness is 0.05×

a lattice constant, a filling factor is not less than 9% and not more than 24%, and an aspect ratio is not less than 1.00 and not more than 1.20;

(4) a roundedness is 0.10×

a lattice constant, a filling factor is not less than 10% and not more than 22%, and an aspect ratio is not less than 1.00 and not more than 1.08;

(5) a roundedness is 0.10×

a lattice constant, a filling factor is not less than 10% and not more than 21%, and an aspect ratio is not less than 1.08 and not more than 1.12;

(6) a roundedness is 0.10×

a lattice constant, a filling factor is not less than 10% and not more than 18%, and an aspect ratio is not less than 1.12 and not more than 1.20;

(7) a roundedness is 0.15×

a lattice constant, a filling factor is not less than 11% and not more than 22%, and an aspect ratio is not less than 1.00 and not more than 1.08;

(8) a roundedness is 0.15×

a lattice constant, a filling factor is not less than 11% and not more than 21%, and an aspect ratio is not less than 1.08 and not more than 1.16;

(9) a roundedness is 0.15×

a lattice constant, a filling factor is not less than 11% and not more than 20%, and an aspect ratio is not less than 1.16 and not more than 1.20;

(10) a roundedness is 0.20×

a lattice constant, a filling factor is not less than 13% and not more than 22%, and an aspect ratio is not less than 1.00 and not more than 1.20,

wherein the roundedness is a radius of the reference circle,

wherein the lattice constant is a length of one side of a unit lattice of the diffraction grating,

wherein the filling factor is a rate of an area of the approximate right triangle of the hole to an area of the unit lattice, and

wherein the aspect ratio is a ratio of a side length of the first side and a side length of the second side on the assumption that the vertices are not rounded.