A method of fabricating at least one radiation emitter including fabricating a layer stack that includes a first reflector, an active region, an oxidizable layer, and a second reflector; and locally removing the layer stack, and thereby forming at least one mesa. The mesa includes the first reflector, the active region, the oxidizable layer and the second reflector. Before or after locally removing the layer stack and forming the mesa the following steps are carried out: vertically etching at least three blind holes inside the layer stack, wherein the blind holes vertically extend to and expose the oxidizable layer; and oxidizing the oxidizable layer via the sidewalls of the blind holes in lateral direction. An oxidation front radially moves outwards from each hole. The etching is terminated before the entire oxidizable layer is oxidized, thereby forming at least one unoxidized aperture that is limited by at least three oxidation fronts.

The present invention discloses a semiconductor laser comprising an optical waveguide structure which may include a lower waveguide layer, an active layer of multiple quantum wells and an upper waveguide layer, which are successively stacked from bottom to top, a grating layer being formed on upper portion of the active layer, wherein the upper waveguide layer, a cladding layer and a contact layer are formed as a ridge which has a light incidence end surface and a light output end surface, wherein a beam expanding structure is formed on one end of the output end surface. The beam expanding structure has a beam expanding portion with a shape gradually contracted inwards from the light output end surface. Preferably, the beam expanding portion has a horizontal divergence angle of 5° to 20°.

A chip scale ultra violet laser source includes a plurality of laser elements on a substrate each including a back cavity mirror, a tapered gain medium, an outcoupler, a nonlinear crystal coupled to the outcoupler with a front facet that has a first coating that is anti-reflectivity (AR) to a fundamental wavelength of the laser element and high reflectivity (HR) to ultra violet wavelengths, and has an exit facet that has a second coating that has HR to a fundamental wavelength of the laser element and AR to the ultra violet wavelengths, a photodetector coupled to the outcoupler, a phase modulator coupled to the photodetector and coupled to the back cavity mirror, and a master laser diode on the substrate coupled to the phase modulator of each laser element. Each laser element emits an ultra violet beamlet and is frequency and phase locked to the master laser diode.

A quantum cascade laser includes a semiconductor substrate and an active layer having a cascade structure, in which unit layered bodies, each composed of a quantum well light emitting layer and an injection layer, are stacked, wherein the unit layered body has a subband level structure having an upper laser level, a lower laser level, and a relaxation miniband composed of at least two energy levels with an energy spacing smaller than the energy difference (E.sub.UL) between the upper laser level and the lower laser level, the energy width of the relaxation miniband is smaller than the energy (E.sub.LO−E.sub.UL) obtained by subtracting the energy difference (E.sub.UL) from the energy (E.sub.LO) of longitudinal optical phonons, and electrons subjected to the intersubband transition are relaxed in the relaxation miniband and are injected into a quantum well light emitting layer in a subsequent unit layered body.

A vertical cavity light-emitting element includes: a first-conductivity-type semiconductor layer; an active layer; a second-conductivity-type semiconductor layer that are formed in this order on a first reflector; an insulating current confinement layer formed on the second-conductivity-type semiconductor layer; a through opening formed in the current confinement layer; a transparent electrode covering the through opening and the current confinement layer and being in contact with the second-conductivity-type semiconductor layer via the through opening; and a second reflector formed on the transparent electrode. At least one of a portion of the transparent electrode corresponding to the opening and a portion of the second-conductivity-type semiconductor layer corresponding to the opening that are in contact with each other in the through opening includes a first resistive region disposed along an inner circumference of the through opening and a second resistive region disposed on a center region of the through opening.

Provided is an optical semiconductor element including: a stacked structure body 20 formed of a first compound semiconductor layer 21, a third compound semiconductor layer (active layer) 23, and a second compound semiconductor layer 22. A fundamental mode waveguide region 40 with a waveguide width W.sub.1, a free propagation region 50 with a width larger than W.sub.1, and a light emitting region 60 having a tapered shape (flared shape) with a width increasing toward a light emitting end surface 25 are arranged in sequence.

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.

Semiconductor device structures comprising laser diode cavities with at least one of a mode-selective filter and a phase-alignment element, and methods for their fabrication, are disclosed. An example device structure comprises a surface-etched grating distributed-feedback (SEG DFB) laser with a mode-selective reflector structure. The reflector structure is designed to provide higher pot feedback of the fundamental TE0 mode and suppression of higher order mode effects. The reflector structure may be a single interface (single facet) mirror type reflector comprising a spatially patterned reflector, or a multi-interface distributed Bragg reflector (DBR). A phase alignment element may be included to provide precise optical phase control. A photodetector for back-facet power monitoring may be included. A method of fabrication is disclosed, based on a self-aligned process in which DBR features are included on the same mask that is used for the DFB laser grating.

A laser including a grating configured to reduce lasing threshold for a selected vertically confined mode as compared to other vertically confined modes.

A VCSEL can include: an electro-optic modulator between a lasing active region and a light emitting surface. The electro-optic modulator can include: an electro-optically active region; a modulator mirror region over the electro-optically active region; and at least one electrical insulator region separating the modulator mirror region into at least two separate modulator mirror cavities electrically isolated from each other, wherein each separate modulator mirror cavity and a longitudinally aligned portion of the electro-optically active region form an electro-optic modulator cavity. A method of emitting light from a VCSEL can include: emitting a laser beam from the lasing active region along a longitudinal axis; and changing a refractive index of one electro-optic modulator cavity so as to steer the laser beam from the longitudinal axis.