A method for forming a Bragg reflector includes after forming first trenches in the stack, which are intended to form structures of the distributed Bragg reflector, forming a sacrificial interlayer at least in the first trenches, depositing a second masking layer at least inside the first trenches, forming second trenches intended to form sidewalls of the laser, removing the second masking layer from inside the first trenches, removing said sacrificial interlayer so as to remove, by lift-off, residues of the second masking layer that remain inside the first trenches, and filling said first trenches with at least one metal material.

Gallium nitride based devices and, more particularly to the generation of holes in gallium nitride based devices lacking p-type doping, and their use in light emitting diodes and lasers, both edge emitting and vertical emitting. By tailoring the intrinsic design, a wide range of wavelengths can be emitted from near-infrared to mid ultraviolet, depending upon the design of the adjacent cross-gap recombination zone. The innovation also provides for novel circuits and unique applications, particularly for water sterilization.

An ICL comprises: a plurality of IC stages, wherein each of the IC stages comprises: a hole injector; an electron injector; an active region coupled to the hole injector and the electron injector and comprising a first layer, wherein the first layer comprises a first material, and wherein the first material comprises InAsP or AlInAsP; a conduction band running through the hole injector, the electron injector, and the active region; and a valence band running through the hole injector, the electron injector, and the active region.

A laser beam irradiation unit of a laser processing apparatus includes a first pulsed laser oscillator that oscillates a pulsed laser having a wavelength of 9 to 11 μm and a pulse width of 5 ns or less, a CO.sub.2 amplifier that amplifies a pulsed laser beam emitted from the first pulsed laser oscillator, and a condenser that focuses the pulsed laser beam amplified by the CO.sub.2 amplifier on a workpiece held on the chuck table.

Semiconductor laser architectures that provide weak index guiding of interband cascade lasers (ICLs) processed on a native III-V substrate and of ICLs grown on GaAs or integrated on GaAs by heterogeneous bonding. Weak index guiding of a ridge waveguide semiconductor laser can enhance the stability of lasing in the fundamental lateral mode, so as to allow a wider ridge to maintain stable single-lateral-mode operation.

A vertical-cavity surface-emitting laser (VCSEL) is provided that includes a mesa structure disposed on a substrate. The mesa structure defines an emission axis of the VCSEL. The mesa structure includes a first reflector, a second reflector, and a cascaded active region structure disposed between the first reflector and the second reflector. The cascaded active region structure includes a plurality of cascaded active region layers disposed along the emission axis, where each of the cascade active region layers includes an active region having multi-quantum well and/or dots layers (MQLs), a tunnel junction aligned with the emission axis, and an oxide confinement layer. The oxide confinement layer is disposed between the tunnel junction and MQLs, and has an electrical current aperture defined therein. The mesa structure defines an optical window through which the VCSEL is configured to emit light.

The laser module includes a QCL element, a diffraction grating unit including a movable diffraction grating, a first lens that transmits light emitted from an end surface of the QCL element and light returning from the movable diffraction grating to the QCL element, a second lens that transmits terahertz waves emitted from the QCL element, a first holder, and a package. The first holder has a support surface on which the QCL element is mounted and a side surface connected to the support surface and facing the first lens in a resonance direction. A distance from an intersection point between the side surface and the support surface to the end surface along the resonance direction is smaller than a distance between the intersection point and the first lens along the resonance direction.

The external cavity laser module includes a quantum cascade laser element, a MEMS diffraction grating, a support plate having a first surface on which the quantum cascade laser element and the MEMS diffraction grating are disposed and a second surface opposite to the first surface, and a cooling element disposed on a side facing the second surface of the support plate to overlap with the quantum cascade laser element and the MEMS diffraction grating. In the second surface of the support plate, a concave portion recessed in a direction from the second surface toward the first surface is provided in at least a region overlapping with the quantum cascade laser element and the MEMS diffraction grating when viewed from the thickness direction. At least a portion of the cooling element facing the support plate is inserted into the concave portion.

A quantum cascade laser element includes: a semiconductor substrate; a semiconductor laminate including an active layer and having a first end surface and a second end surface facing each other in an optical waveguide direction; a first electrode; a second electrode; and an anti-reflection film formed on the first end surface. The semiconductor laminate is configured to oscillate laser light having a central wavelength of 7.5 μm or more. The anti-reflection film includes at least one of at least one layer of a CeO.sub.2 film formed by continuous sputtering and vacuum evaporation and a plurality of layers of CeO.sub.2 films formed by discrete sputtering and vacuum evaporation.

A laser assembly (10) for generating a pulsed output beam (16) includes a quantum cascade device (12); and a laser driver (14A) that controls the voltage to the quantum cascade device (12) in a pulsed drive profile (950) to generate the pulsed output beam (16). The pulsed drive profile (950) includes a plurality of spaced on-time segments (952) in which the laser driver (14A) directs voltage to the quantum cascade device (12), and at least one off-time segment (954) in which the laser driver (14A) pulls down the voltage from the quantum cascade device (12). The off-time segment (954) occurs between two on-time segments (952).