Surface-emitting quantum cascade laser

Patent metadata

Field	Value
Publication number	US-10490977-B2
Application number	US-201816185875-A
Country	US
Kind code	B2
Filing date	Nov 9, 2018
Priority date	Nov 16, 2017
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.

First claim

What is claimed is:

1. A surface-emitting quantum cascade laser comprising:
a substrate;
an active layer provided on the substrate, having optical nonlinearity, and being capable of emitting a first and a second infrared laser light by intersubband transition; and
a photonic crystal layer placed on the active layer and including a first region provided with a rectangular grating having optical anisotropy and a second region provided with the rectangular grating, the rectangular grating of the first region being orthogonal to the rectangular grating of the second region,
in the first region, the first infrared laser light having a first wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating, and the first infrared laser light lasing in the direction parallel to the first side,
in the second region, the second infrared laser light having a second wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating, and the second infrared laser light lasing in the direction parallel to the second side,
part of the first infrared laser light flowing into the second region and being capable of existing in the second region, and
the first and second infrared laser light being emitted in a direction generally perpendicular to the active layer.

2. The laser according to claim 1 , wherein the second wavelength corresponds to a gain spectrum peak.

3. The laser according to claim 1 , wherein
the first region and the second region are arranged in a checkerboard pattern, and
in each region constituting the checkerboard pattern, difference frequency light of the first infrared laser light and the second infrared laser light is generated by Cherenkov phase matching based on the optical nonlinearity and emitted outward as a terahertz wave from the substrate.

4. The laser according to claim 2 , wherein
the first region and the second region are arranged in a checkerboard pattern, and
in each region constituting the checkerboard pattern, difference frequency light of the first infrared laser light and the second infrared laser light is generated by Cherenkov phase matching based on the optical nonlinearity and emitted outward as a terahertz wave from the substrate.

5. The laser according to claim 1 , wherein the first photonic bandgap is larger than the second photonic bandgap.

6. The laser according to claim 2 , wherein the first photonic bandgap is larger than the second photonic bandgap.

7. The laser according to claim 3 , wherein the first photonic bandgap is larger than the second photonic bandgap.

8. The laser according to claim 1 , wherein
the rectangular grating is composed of pit parts having a lower refractive index than the photonic crystal layer therearound, length of each pit part in the direction parallel to the first side is larger than length parallel to the second side, and
the each pit part is shaped to be asymmetric with respect to lines passing through a barycenter of the each pit part and being parallel to the first side and the second side, respectively.

9. The laser according to claim 3 , wherein depressions capable of refracting the difference frequency light to a perpendicular outward direction are two-dimensionally provided in a back surface of the substrate.

10. The laser according to claim 3 , further comprising:
a lower electrode provided on a back surface of the substrate and reflecting the difference frequency light upward.

11. The laser according to claim 3 , further comprising:
a lower electrode provided on a back surface of the substrate and provided with an opening,
the difference frequency light being emitted outside through the opening.

12. The laser according to claim 8 , further comprising:
an upper electrode having a frame shape and provided in a peripheral part of the each region, wherein
the each pit part is provided so as not to overlap the upper electrode.

Assignees

• Toshiba Kk

Inventors

• Hashimoto Rei
• Saito Shinji
• Yamamoto Yuichiro
• Kakuno Tsutomu
• Kaneko Kei
• Takase Tomohiro

Classifications

• H01S5/04254

  characterised by the shape · CPC title

• H01S2302/02

  THz - lasers, i.e. lasers with emission in the wavelength range of typically 0.1 mm to 1 mm · CPC title

• H01S5/0604

  comprising a non-linear region, e.g. generating harmonics of the laser frequency · CPC title

• H01S5/22

  having a ridge or stripe structure · CPC title

• H01S5/0207

  Substrates having a special shape · CPC title