A vertical cavity surface emitting laser (VCSEL) has a shortened overall laser cavity by combining the gain section with a distributed Bragg reflector (DBR). The overall cavity length can be contracted by placing gain structures inside the DBR. This generally applies to a number of semiconductor material systems and wavelength bands, but this scheme is very well suited to the AlGaAs/GaAs material system with strained InGaAs quantum wells as a gain medium, for example.

An apparatus for outputting directional light includes a light-emitting structure including a light-emitting layer that emits light, and an optical antenna layer disposed on the light-emitting structure, wherein the optical antenna layer includes a light feeder configured to resonate light output from the light-emitting layer and a light reflector configure to reflect light output from the light feeder to have directivity. The light feeder and the light reflector are formed on a surface of the optical antenna layer.

A nitride semiconductor light-emitting device with periodic gain active layers includes an n-type semiconductor layer, a p-type semiconductor layer and a resonator. The device further includes a plurality of active layers disposed between the n-type and p-type semiconductor layers so as to correspond to a peak intensity position of light existing in the resonator and at least one interlayer disposed between the active layers. The active layer disposed at the p-type semiconductor layer side has a larger light emission intensity than the active layer disposed at the n-type semiconductor layer side.

An intra-cavity doubled OPS-laser has a laser-resonator including a birefringent filter (BRF) for coarse wavelength-selection, and an optically nonlinear (ONL) crystal arranged for type-II frequency-doubling and fine wavelength-selection. Laser-radiation circulates in the laser-resonator at one of a range of fundamental wavelengths dependent on the resonator length. The ONL crystal has a transmission peak-wavelength dependent on the crystal temperature. Reflection of circulating radiation from the BRF is monitored. The reflection is at a minimum when the ONL crystal transmission-peak wavelength is at the circulating radiation wavelength. The temperature of the ONL crystal is selectively varied to maintain the monitored reflection at about a minimum.

A very strong selection mechanism is provided in a tunable vertical cavity surface emitting laser (VCSEL) by manipulating the laser threshold to be different for TE and TM polarization by a employing a subwavelength grating in the laser cavity. The laser selects the polarization with the lowest threshold. The grating does not diffract and does not add loss to the cavity. It works by creating a large birefringence layer between the semiconductor and air sub-cavities of the full VCSEL. Multilayer stack calculations show that this results in a lower threshold for the TM polarization over the TE. This subwavelength grating layer, in one embodiment, replaces the AR coating on the semiconductor surface.

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.

A vertical cavity surface emitting laser (VCSEL) may include an epitaxial structure that includes a first active layer, a second active layer, and a tunnel junction therebetween. The VCSEL may include a set of contacts that are electrically connected to the epitaxial structure. The set of contacts may include three or more contacts, and the set of contacts may be electrically separated from each other on the VCSEL. At least one contact, of the set of contacts, may be electrically connected to the epitaxial structure at a depth between the first active layer and the second active layer.

A vertical cavity surface emitting laser (VCSEL) may include an epitaxial structure that includes a first active layer, a second active layer, and a tunnel junction therebetween. The VCSEL may include a set of contacts that are electrically connected to the epitaxial structure. The set of contacts may include three or more contacts, and the set of contacts may be electrically separated from each other on the VCSEL. At least one contact, of the set of contacts, may be electrically connected to the epitaxial structure at a depth between the first active layer and the second active layer.

A multi-junction VCSEL is formed by as a compact structure that reduces lateral current spreading by reducing the spacing between adjacent active regions in the stack of such regions used to from the multi-junction device. At least two of the active regions within the stack are located adjacent peaks of the intensity profile of the VCSEL, with an intervening tunnel junction positioned at a trough between the two peaks. The alignment of the active regions with the peaks maximizes the generated optical power, while the alignment of the tunnel junction with the trough minimizes optical loss. The close spacing on adjacent peaks forms a compact structure (which may even include a cavity having a sub-λ optical length) that lessens the total path traveled by carriers and therefore reduces lateral current spread.

Disclosed herein are self-mixing interferometry (SMI) sensors, such as may include vertical cavity surface emitting laser (VCSEL) diodes and resonance cavity photodetectors (RCPDs). Structures for the VCSEL diodes and RCPDs are disclosed. In some embodiments, a VCSEL diode and an RCPD are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate. In some embodiments, a first and a second VCSEL diode are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate, and an RCPD is formed on the second VCSEL diode. In some embodiments, a VCSEL diode may include two quantum well layers, with a tunnel junction layer between them. In some embodiments, an RCPD may be vertically integrated with a VCSEL diode.