A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.
A novel quantum cascade (QC) laser comprises a multiplicity of identical repeat units, with each repeat unit comprising an active region and an injector region. The injector region comprises quantum wells and barriers, selected to facilitate, under appropriate bias, resonant carrier transport from a lower energy level of a given active region to an upper energy level of an adjacent downstream active region. Carrier transition from the upper energy level to a lower energy level of an active region results in emission of infrared radiation. The laser is advantageously used in, e.g., a measurement system for detection of trace compounds in air.
A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.
A novel superlattice quantum cascade (SLQC) laser has undoped SL active regions, with the dopant concentration in the injector region being selected, such that, under an appropriate electrical bias, the SL active region is substantially electric field free. The absence of dopant atoms in the SL active region results in reduced carrier scattering and reduced optical losses, with consequent low threshold current and/or room temperature operation. The novel laser emits in the mid-IR spectral region and can be advantageously used in measurement or monitoring systems, e.g., in pollution monitoring systems.
A QC laser comprises first and second optical confinement (i.e., cladding) regions, and an In-based, Group III-V compound, QC active region disposed between the confinement regions. At least the first confinement region and the active region having the shape of an elongated mesa. An i-type InP layer covers the sidewalls to provide efficient heat transport and effective low loss mode confinement. A metal layer makes ohmic contact with the top surface of the mesa and a rectifying contact with the i-InP layer.