DISTRIBUTED FEEDBACK LASER BASED ON SURFACE GRATING

• US 20190319426A1
• Filed: 06/21/2019
• Published: 10/17/2019
• Est. Priority Date: 12/22/2016
• Status: Active Grant

• Current Assignee: Huazhong University of Science & Technology
• Original Assignee: Huazhong University of Science & Technology
• Inventors: LU, Qiaoyin, ZHANG, Pengfei, GUO, Weihua
• Granted Patent: US 10,811,842 B2
• Time in Patent Office: Days
• CPC Class Codes: H01S 5/0014 Measuring characteristics or properties thereof measuring techniques per se G01J, G01K, G01N, G01R
• CPC Class Codes: H01S 5/0287 Facet reflectivity
• CPC Class Codes: H01S 5/0425 Electrodes, e.g. characterised by the structure
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/12 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18
• CPC Class Codes: H01S 5/1206 having a non constant or multiplicity of periods
• CPC Class Codes: H01S 5/124 incorporating phase shifts
• CPC Class Codes: H01S 5/125 Distributed Bragg reflector [DBR] lasers
• CPC Class Codes: H01S 5/2063 obtained by particle bombardment
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/2215 using native oxidation of semiconductor layers
• CPC Class Codes: H01S 5/2226 semiconductors with a specific doping
• CPC Class Codes: H01S 5/3095 Tunnel junction
• CPC Class Codes: H01S 5/3211 characterised by special cladding layers, e.g. details on band-discontinuities

Abstract

A distributed feedback laser, including: a ridge waveguide; two upper electrodes disposed on two sides of the ridge waveguide, respectively; two lower electrodes disposed on two sides of the upper electrodes, respectively; a substrate; a second waveguide cladding layer; an active layer; and a first waveguide cladding layer. The first waveguide cladding layer is n-doped and includes a conductive layer and a refractive layer disposed on the conductive layer. The refractive index of the refractive layer is greater than the refractive index of the active layer. The ridge waveguide includes a ridge region formed by a middle part of the refractive layer. The ridge region includes a surface provided with Bragg gratings. Two grooves are formed between the ridge waveguide and the upper electrodes. The conductive layer is connected to the upper electrodes. The second waveguide cladding layer includes one or more current restricted areas.

Claims

1. A distributed feedback laser, comprising:

a ridge waveguide;

two upper electrodes disposed on both sides of the ridge waveguide, respectively;

two lower electrodes disposed on two sides of the upper electrodes, respectively;

a substrate;

a second cladding layer;

an active layer; and

a first cladding layer;

wherein;

the first cladding layer is n-doped and comprises a conductive layer and a refractive layer disposed on the conductive layer;

a refractive index of the refractive layer is greater than that of the active layer;

the refractive layer has a thickness of less than 1 micrometer;

a ridge region of the ridge waveguide is formed in an intermediate portion of the refractive layer, and the Bragg grating is etched on the surface of the ridge region;

two grooves are formed between the ridge waveguide and the upper electrodes;

the conductive layer is connected to the upper electrodes;

the second cladding layer comprises one or more current limited regions, or a buried tunnel junction is formed in the first cladding layer for restricting current; and

the second cladding layer comprises an ohmic contact layer which is connected to the two lower electrodes.

2. The laser of claim 1, wherein a light field of the ridge region forms an interaction with the Bragg grating, and the coupling coefficient of the Bragg grating can be greater than 250 cm⁻

1.

3. The laser of claim 1, wherein the Bragg gratings are first-order gratings comprising one or more phase shift regions of λ

_B/4, or are high-order gratings;

a period of the Bragg gratings is ∧

=mλ

_B/2n_eff , where λ

_B and m are a Bragg wavelength and an order of the gratings, respectively, and n_eff is an effective refractive index of the waveguide.

4. The laser of claim 1, wherein the conductive layer is n-doped.

5. The laser of claim 1, wherein the two grooves extend to the conductive layer, and a width of the two grooves is greater than 500 nanometers.

6. The laser of claim 1, wherein the upper electrode is N-type electrode, and the lower electrode is P-type electrode.

7. The laser of claim 2, wherein the active layer is not doped, and comprises an active layer and one or more confinement layers;

the active layer consists of multi-quantum wells, quantum wires, quantum dots, or bulk material.

8. The laser of claim 1, wherein the second cladding layer is p-doped;

the first cladding layer, the active layer, and the second cladding layer form an N-i-P structure;

a current confinement region is formed at a position near the active layer in the second cladding layer to limit the injection of holes, so that the hole injection region and the ridge waveguide mode can be maximally overlapped.

10. The laser of claim 1, wherein the ohmic contact layer is p-doped and has a doping density ranging from 10¹⁹ to 10²⁰ cm⁻

3.

9. The laser of claim 11, wherein a method for forming the current limiting region comprises:

forming by ion implantation into a corresponding region;

or forming a aluminum-rich layer in a corresponding region, and then oxidizing the aluminum-rich layer from both sides to form aluminum oxide, thereby forming a high resistance region;

or a tunnel junction is used above the active layer region to limit the injection of holes.