Two-dimensional photonic crystal surface-emitting laser light source

• US 20090279579A1
• Filed: 08/28/2006
• Published: 11/12/2009
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: Kyoto University, ROHM Co., Ltd.
• Original Assignee: Kyoto University, ROHM Co., Ltd.
• Inventors: Noda, Susumu, Miyai, Eiji, Kunishi, Wataru, Ohnishi, Dai
• Granted Patent: US 8,379,686 B2
• Time in Patent Office: Days
• US Class Current: 372/50.124
• CPC Class Codes: H01S 2301/18 Semiconductor lasers with special structural design for influencing the near- or far-field
• CPC Class Codes: H01S 5/0215 Bonding to the substrate
• CPC Class Codes: H01S 5/0234 Up-side down mountings, e.g. Flip-chip, epi-side down mountings or junction down mountings
• CPC Class Codes: H01S 5/024 Arrangements for thermal management
• CPC Class Codes: H01S 5/04254 characterised by the shape
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/1021 Coupled cavities H01S5/14 takes precedence
• CPC Class Codes: H01S 5/1039 Details on the cavity length
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity

Abstract

The present invention provides a two-dimensional photonic crystal surface-emitting laser light source capable of producing a beam that is not accompanied by unnecessary side lobes. A window-shaped electrode 36 having a central window 361 devoid of the electrode material is provided on the surface of a device substrate 31 from which surface emission is extracted. A mount surface electrode 37 having an area smaller than that of the window-shaped electrode 36 including the window 361 is provided on a mount surface 38. The distance between the device substrate 31 and the active layer 32 is larger than that between the mount surface 38 and the active layer 32. When a voltage is applied between the electrodes, electric charges are injected into the active layer and emission is obtained. Then, a component of light having a specific wavelength is amplified by a two-dimensional photonic crystal 33, whereby a laser oscillation is produced. The laser light is extracted through the window 361 to the outside. Since the window-shaped electrode 36 does not block the emission of light, the emitted light never forms side lobes due to interference. The positioning of the active layer 32 close to the mount surface 38 significantly enhances the heat-radiating effect.

Claims

1. A two-dimensional photonic crystal surface-emitting laser light source, comprising:

a) a substrate made of a material that is transparent to light having an objective wavelength;

b) an active layer located below the substrate;

c) a two-dimensional photonic crystal for amplifying light having the objective wavelength, where the two-dimensional photonic crystal is located either between the substrate and the active layer or below the active layer and includes a plate-shaped body material in which a large number of modified refractive index areas whose refractive index differs from that of the body material are periodically arranged;

d) a mount layer to be in contact with an external member when the light source is mounted, where the mount layer is located below the two-dimensional photonic crystal and the active layer in such a manner where a distance between a lower surface of the mount layer and the active layer is smaller than a distance between an upper surface of the substrate and the active layer;

e) a window-shaped electrode on the upper surface of the substrate, where the electrode has a window for allowing laser light having the objective wavelength to pass through; and

f) a mount surface electrode located on the lower surface of the mount layer and having an area smaller than that of the window-shaped electrode inclusive of an area of the window.

2. The two-dimensional photonic crystal surface-emitting laser light source according to claim 1, wherein:

a ratio of an area of the window-shaped electrode including the area of the window to that of the mount surface electrode is within a range from 2;

1 to 400;

1 and a ratio of the distance between the upper surface of the substrate and the active layer to the distance between the lower surface of the mount surface and the active layer is within a range from 2;

1 to 400;

1.

3. The two-dimensional photonic crystal surface-emitting laser light source according to claim 1, wherein:

the modified refractive index areas are arranged in a square lattice pattern and have an asymmetrical shape with respect to at least one of axes of the square lattice pattern.

4. The two-dimensional photonic crystal surface-emitting laser light source according to claim 3, wherein:

the modified refractive index areas have an equilateral-triangular shape.

5. The two-dimensional photonic crystal surface-emitting laser light source according to claim 1, wherein:

a reflector for reflecting the laser light having the objective wavelength is provided below a laser oscillator consisting of the active layer and the two-dimensional photonic crystal.

6. The two-dimensional photonic crystal surface-emitting laser light source according to claim 5, wherein:

the reflector is located between the laser oscillator and the mount surface electrode.

7. The two-dimensional photonic crystal surface-emitting laser light source according to claim 5, wherein:

the mount layer is made of a conductive material, a portion of the lower surface of the mount layer is defined as a conductive area, and an insulating area is created around the conductive area; and

the mount surface electrode made of a material reflecting the laser light having the objective wavelength is placed so that it covers the insulating area.

8. The two-dimensional photonic crystal surface-emitting laser light source according to claim 7, wherein:

the insulating area is created by injecting resistance-increasing ions into the mount layer.

9. The two-dimensional photonic crystal surface-emitting laser light source according to claim 5, wherein:

a distance between the laser oscillator and the reflector is set so that a reflected light emitted from the laser oscillator and then reflected by the reflector constructively interferes with a light directly emitted from the laser oscillator to the side on which the window-shaped electrode is located.

10. The two-dimensional photonic crystal surface-emitting laser light source according to claim 9, wherein:

the distance between the laser oscillator and the reflector is adjusted by one or more distance-adjusting layers located between the laser oscillator and the reflector.

11. The two-dimensional photonic crystal surface-emitting laser light source according to claim 1, wherein:

the active layer is a multi-quantum well of InGaAs/GaAs; and

the substrate is an n-type GaAs.