Provided is a laser device according to an embodiment of the inventive concept. The laser device includes: a semiconductor substrate; a germanium single crystal layer on the semiconductor substrate; and a pumping light source disposed on the germanium single crystal layer and configured to emit light toward the germanium single crystal layer, wherein the germanium single crystal layer receives the light to thereby output laser.

Disclosed herein are embodiments of a vertical external cavity surface emitting laser (VECSEL) device that utilizes an external micromirror array, and methods of fabricating and using the same. In one embodiment, a VECSEL device includes a gain chip, a mirror, and a micromirror array. The gain chip includes a gain medium. The micromirror array includes a plurality of curved micromirrors. The micromirror array and the mirror define an optical cavity, and the micromirror array is oriented such that at least one of the curved micromirrors is to reflect light generated by the gain medium back toward the gain medium along a length of the optical cavity.

A tunable laser includes a reflective silicon optical amplifier (RSOA) with a reflective end and an interface end and an array of narrow-band reflectors, which each have a different center wavelength. It also includes a silicon-photonic optical switch, having an input port and N output ports that are coupled to a different narrow-band reflector in the array of narrow-band reflectors. The tunable laser also includes an optical waveguide coupled between the interface end of the RSOA and the input of the silicon-photonic optical switch. The frequency of this tunable laser can be tuned in discrete increments by selectively coupling the input port of the silicon-photonic optical switch to one of the N output ports, thereby causing the RSOA to form a lasing cavity with a selected narrow-band reflector coupled to the selected output port. The tunable laser also includes a laser output optically coupled to the lasing cavity.

A vertical external-cavity surface-emitting laser (VECSEL) whose blueshift is reduced also in a high intensity range of emitted laser light is realized. A surface-emitting device for VECSEL includes a base substrate made of GaN and c-axis oriented, and an emitter structure formed of a group 13 nitride semiconductor and provided on the base substrate. The emitter structure is formed of unit deposition parts, each of which is provided on the base substrate and includes a DBR layer having a distributed Bragg reflection structure and an active layer that has a multiple quantum well structure and generates excitation emission in response to irradiation with external laser light. A c-axis orientation of each of the unit deposition parts conforms to the c-axis orientation of the base substrate located directly below the unit deposition parts. Grooves are formed between the unit deposition parts.

A laser element includes a photonic crystal layer on which laser light is incident. The photonic crystal layer includes a base layer formed of a first refractive index medium; and a plurality of different refractive index regions formed of a second refractive index medium having a refractive index different from that of the first refractive index medium and disposed in the base layer. The plurality of different refractive index regions includes a first different refractive index region of which a planar shape is an approximate circle, an approximate square, or an approximate polygon having a rotational symmetry of 90° and a first area perpendicular to a thickness direction; and a second different refractive index region having a second area perpendicular to a thickness direction.

A laser element includes a photonic crystal layer on which laser light is incident. The photonic crystal layer includes a base layer formed of a first refractive index medium; and a plurality of different refractive index regions formed of a second refractive index medium having a refractive index different from that of the first refractive index medium and disposed in the base layer. The plurality of different refractive index regions includes a first different refractive index region of which a planar shape is an approximate circle, an approximate square, or an approximate polygon having a rotational symmetry of 90° and a first area perpendicular to a thickness direction; and a second different refractive index region having a second area perpendicular to a thickness direction.

A vertical cavity surface emitting laser includes: a substrate; a first mirror layer; an active layer; a second mirror layer; a current constriction layer; a first area connected to the first mirror layer and including a plurality of oxide layers; and a second area connected to the second mirror layer and including a plurality of oxide layers. The first mirror layer, the active layer, the second mirror layer, the current constriction layer, the first area, and the second area configure a laminated body. The laminated body includes a first portion, a second portion, and a third portion between the first portion and the second portion. When a width of the oxide area is W1 and a width of an upper surface of the first portion is W2, W2/W1≦3.3.

A vertical cavity surface emitting laser includes: a substrate; a first mirror layer; an active layer; a second mirror layer; a current constriction layer; a first area connected to the first mirror layer and including a plurality of oxide layers; and a second area connected to the second mirror layer and including a plurality of oxide layers. The first mirror layer, the active layer, the second mirror layer, the current constriction layer, the first area, and the second area configure a laminated body. The laminated body includes a first portion, a second portion, and a third portion between the first portion and the second portion. When a width of the oxide area is W1 and a width of an upper surface of the first portion is W2, W2/W1≦3.3.

Aspects of the subject disclosure may include, for example, a first distributed Bragg reflector, a second distributed Bragg reflector, an active region with an oxide aperture between the first and second distributed Bragg reflectors, and a dielectric layer, where a positioning of the dielectric layer with respect to the first and second distributed Bragg reflectors and the oxide aperture causes suppression of higher modes of the vertical-cavity surface-emitting laser device. Other embodiments are disclosed.

Disclosed is a current-injection organic semiconductor laser diode comprising a pair of electrodes, an optical resonator structure, and one or more organic layers including a light amplification layer composed of an organic semiconductor, which has a sufficient overlap between the distribution of excitor density and the electric field intensity distribution of the resonant optical mode during current injection to emit laser light.