A quantum cascade laser is configured with a semiconductor substrate, and an active layer provided on a first surface of the substrate and having a cascade structure in the form of a multistage lamination of unit laminate structures each of which includes an emission layer and an injection layer. The active layer is configured to be capable of generating first pump light of a frequency .sub.1 and second pump light of a frequency .sub.2 by intersubband emission transitions of electrons, and to generate output light of a difference frequency by difference frequency generation from the first pump light and the second pump light. Grooves respectively formed in a direction intersecting with a resonating direction in a laser cavity structure are provided on a second surface opposite to the first surface of the substrate.

A quantum cascade laser is configured with a semiconductor substrate, and an active layer provided on a first surface of the substrate and having a cascade structure in the form of a multistage lamination of unit laminate structures each of which includes an emission layer and an injection layer. The active layer is configured to be capable of generating first pump light of a frequency .sub.1 and second pump light of a frequency .sub.2 by intersubband emission transitions of electrons, and to generate output light of a difference frequency by difference frequency generation from the first pump light and the second pump light. Grooves respectively formed in a direction intersecting with a resonating direction in a laser cavity structure are provided on a second surface opposite to the first surface of the substrate.

The present disclosure falls into the field of optoelectronics, particularly, includes the design, epitaxial growth, fabrication, and characterization of Laser Diodes (LDs) operating in the ultraviolet (UV) to infrared (IR) spectral regime on patterned substrates (PSs) made with (formed on) low cost, large size Si, or GaN on sapphire, GaN, and other wafers. We disclose three types of PSs, which can be universal substrates, allowing any materials (III-Vs, II-VIs, etc.) grown on top of it with low defect and/or dislocation density.

The present disclosure falls into the field of optoelectronics, particularly, includes the design, epitaxial growth, fabrication, and characterization of Laser Diodes (LDs) operating in the ultraviolet (UV) to infrared (IR) spectral regime on patterned substrates (PSs) made with (formed on) low cost, large size Si, or GaN on sapphire, GaN, and other wafers. We disclose three types of PSs, which can be universal substrates, allowing any materials (III-Vs, II-VIs, etc.) grown on top of it with low defect and/or dislocation density.

An optical waveguide structure includes: a first waveguide that has a layered structure in which layering is performed in a first direction, includes a first core layer that extends in a second direction, and a first cladding layer that has an end surface in the second direction; and a second waveguide that has a layered structure in which layering is performed in the first direction, includes a second core layer that is adjacent to the first core layer in the second direction, that is optically connected to the first core layer, and that, at least in an end portion of the second waveguide in an opposite direction to the second direction, extends in the second direction, and a second cladding layer that sandwiches the second core layer in the first direction.

In a semiconductor laser device, a light shielding groove is formed in an upper cladding layer so as to be adjacent to a bank in a waveguide direction. A surface of the light shielding groove is covered with an insulating layer (not illustrated), and a depth of the light shielding groove reaches an absorption layer that is either a substrate or a buffer layer formed on the substrate.

In a semiconductor laser device, a light shielding groove is formed in an upper cladding layer so as to be adjacent to a bank in a waveguide direction. A surface of the light shielding groove is covered with an insulating layer (not illustrated), and a depth of the light shielding groove reaches an absorption layer that is either a substrate or a buffer layer formed on the substrate.