SURFACE-EMITTING QUANTUM CASCADE LASER

• US 20190148915A1
• Filed: 11/13/2018
• Published: 05/16/2019
• Est. Priority Date: 11/16/2017
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: SAITO, Shinji, TAKASE, Tomohiro, HASHIMOTO, Rei, KAKUNO, Tsutomu
• Granted Patent: US 10,447,012 B2
• Time in Patent Office: Days
• CPC Class Codes: H01S 5/02469 Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC
• CPC Class Codes: H01S 5/02476 Heat spreaders, i.e. improving heat flow between laser chip and heat dissipating elements
• CPC Class Codes: H01S 5/04254 characterised by the shape
• CPC Class Codes: H01S 5/1014 Tapered waveguide, e.g. spotsize converter H01S5/1064 takes precedence
• CPC Class Codes: H01S 5/1021 Coupled cavities H01S5/14 takes precedence
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/1203 over only a part of the length of the active region
• CPC Class Codes: H01S 5/18386 Details of the emission surface for influencing the near- or far-field, e.g. a grating on the surface
• 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 5/3401 having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers
• CPC Class Codes: H01S 5/3402 intersubband lasers, e.g. transitions within the conduction or valence bands
• CPC Class Codes: H01S 5/3407 characterised by special barrier layers

Abstract

A surface-emitting quantum cascade laser of an embodiment includes a semiconductor stacked body, an upper electrode, and a lower electrode. The semiconductor stacked body includes an active layer that includes a quantum well layer and emits infrared laser light, a first semiconductor layer that includes a photonic crystal layer in which pit parts constitute a rectangular grating, and a second semiconductor layer. The upper electrode is provided on the first semiconductor layer. The lower electrode is provided on a lower surface of a region of the second semiconductor layer overlapping at least the upper electrode. The photonic crystal layer is provided on the upper surface side of the first semiconductor layer. In plan view, the semiconductor stacked body includes a surface-emitting region including the photonic crystal layer and a current injection region. The upper electrode is provided on the current injection region.

Claims

1. A surface-emitting quantum cascade laser comprising:

a semiconductor stacked body including an active layer that includes a quantum well layer causing intersubband transition and that emits infrared laser light, a first semiconductor layer that is provided on the active layer and that includes a photonic crystal layer in which pits constitute a rectangular grating, and a second semiconductor layer provided below the active layer;

an upper electrode provided on an upper surface of the first semiconductor layer; and

a lower electrode provided on a lower surface of a region of the second semiconductor layer overlapping at least the upper electrode,

the photonic crystal layer being provided on the upper surface side of the first semiconductor layer,

a planar shape of an opening end of each of the pits being asymmetric with respect to lines passing through a barycenter of the planar shape and being respectively parallel to two sides of the rectangular grating,

in plan view, the semiconductor stacked body including a surface-emitting region including the photonic crystal layer and a current injection region extending radially outward from an outer edge of the surface-emitting region,

the upper electrode being provided on the current injection region of the upper surface of the first semiconductor layer, and

the active layer generating a gain by the intersubband transition based on a current flowing between the upper electrode and the lower electrode in the current injection region to enable emission of the infrared laser light in a direction generally perpendicular to the surface-emitting region while causing optical resonance based on the rectangular grating in the surface-emitting region.

2. The laser according to claim 1, wherein the current injection region is provided along two lines orthogonal to each other on the upper surface of the first semiconductor layer.

3. The laser according to claim 2, wherein the current injection region is orthogonal to at least one of the two sides of the rectangular grating.

4. The laser according to claim 1, further comprising:

a metal layer covering the surface-emitting region including the pits of the photonic crystal layer,

the lower electrode being provided with an opening enabling the infrared laser light reflected by the metal layer to be emitted outward, and

an upper surface of the metal layer and an upper surface of the upper electrode serve as a heat sink attachment surface.

5. The laser according to claim 1, wherein part of the quantum well layer of the active layer of the surface-emitting region is disordered.

6. The laser according to claim 1, wherein part of the quantum well layer of the active layer of the surface-emitting region is oxidized.

7. The laser according to claim 1, further comprising:

a tapered resonator between the current injection region and the surface-emitting region,

the infrared laser light being single-mode, and

a region of minimum taper width of the tapered resonator being connected to the surface-emitting region.

8. The laser according to claim 7, wherein the tapered resonators are provided like a parallel array.