Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

The present technology can be used to control the current injection profile in the longitudinal direction of a high-power diode laser in order to optimize current densities as a function of position in the cavity to promote higher reliable output power and increase the electrical to optical conversion efficiency of the device beyond the level which can be achieved without application of this technique. This approach can be utilized, e.g., in the fabrication of semiconductor laser chips to improve the output power and wall plug efficiency for applications requiring improved performance operation.

According to an aspect of the present inventive concept there is provided a light emitting unit, for emitting laser light at a laser wavelength, arranged on a planar surface of a substrate. The unit comprises a first reflective element to reflect light at the laser wavelength, a gain element to amplify the light, and a second reflective element to partially reflect the light, and to emit the laser light. The elements form a stack of layers integrated onto the planar surface. Each layer is parallel with the planar surface, and the gain element is arranged between the first and second reflective elements.

The unit comprises a beam shaping element integrated with the stack. The beam shaping element is configured to shape the emitted laser light. The beam shaping element comprises a plurality of structures spaced apart in a direction of an extension of a layer of the beam shaping element. A size of the structures and/or a distance between adjacent structures is smaller than the laser wavelength.

Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

A semiconductor laser element includes a substrate and a semiconductor stack. The semiconductor stack includes an N-side semiconductor layer, an active layer, a P-side semiconductor layer, and a P-type contact layer. The semiconductor stack includes two end faces. Laser light resonates between the two end faces. The semiconductor stack includes: a ridge portion; and a bottom portion surrounding the ridge portion in a top view of the semiconductor stack. The ridge portion protrudes upward from the bottom portion, is spaced apart from the two end faces, and includes at least a portion of the P-type contact layer. A current injection window is provided only on the ridge portion out of a top face of the semiconductor stack, the current injection window being a region into which a current is injected. A distance from a top face of the active layer to the bottom portion is constant.

Disclosed herein are multi-layered optically active regions for semiconductor light-emitting devices (LEDs) that incorporate intermediate carrier blocking layers, the intermediate carrier blocking layers having design parameters for compositions and doping levels selected to provide at least one strain compensation layer and efficient control over the carrier injection distribution across the active regions to achieve desired device injection characteristics. Examples of embodiments discussed herein include, among others: a multiple-quantum-well variable-color LED operating in visible optical range with full coverage of RGB gamut, a multiple-quantum-well variable-color LED operating in visible optical range with an extended color gamut beyond standard RGB gamut, a multiple-quantum-well light-white emitting LED with variable color temperature, and a multiple-quantum-well LED with uniformly populated active layers.

An emitter array, may comprise a first set of emitters that has a nominal optical output power at an operating voltage. The emitter array may comprise a second set of emitters that has substantially less than the nominal optical output power or no optical output power at the operating voltage. The first set of emitters and the second set of emitters may be interleaved with each other to form a two-dimensional regular pattern of emitters that emits a random pattern of light at the nominal optical output power at the operating voltage. The first set of emitters and the second set of emitters may be electrically connected in parallel.

A waveguide structure (IOO) for a photonic integrated circuit, comprising: a substrate; an active region (102) comprising a diode junction, the active region comprising: a light emission portion (102a) to emit light in a first direction and a second direction perpendicular the first direction; and a light absorption portion (102b) to absorb light emitted from the light emission portion (102a) in the second direction; a first contact corresponding to the light emission portion (102a); and a second contact corresponding to the light absorption portion (102b).

A semiconductor light-emitting element includes: an n-type cladding layer formed of a nitride semiconductor; an active layer which is arranged above the n-type cladding layer and formed of a nitride semiconductor; a p-type cladding layer arranged above the active layer and formed of a nitride semiconductor; and a p-side electrode arranged above the p-type cladding layer, wherein the p-type cladding layer contains hydrogen, and a first concentration of the hydrogen at a center of the p-type cladding layer in a region below the p-side electrode is lower than a second concentration of the hydrogen at a position located on a side closer to an outer edge than to the center in the region below the p-side electrode.