A method for generating light emission is provided. The method includes providing a transistor element including collector, emitter, and base regions, a quantum cascade region between the base and collector regions, and quantum well structures for interband emission within the base or emitter regions. A waveband controller applies, via first and second electrodes with respect to the collector and base regions, a first electrical signal to control a base-collector junction bias level and select between first and second base-collector bias levels. Selection of the first base-collector bias level causes at least one of the emitter and base regions to produce interband-based light emission having a first wavelength of a first wavelength band. Selection of the second base-collector bias level causes the quantum cascade region to produce intraband-based light emission having a second wavelength of a second wavelength band.

A broad-spectrum laser for use in a MEMS laser scanning display device is provided. In one example, the broad-spectrum laser includes a laser diode emitter with plural quantum wells each having a different spectral peak. In another example, the broad-spectrum laser includes a laser diode emitter with a tunable absorber to achieve a broadened emissions spectrum. In another example, the broad-spectrum laser includes a laser diode emitter array having plural individual emitters with different spectral peaks.

A broad-spectrum laser for use in a MEMS laser scanning display device is provided. In one example, the broad-spectrum laser includes a laser diode emitter with plural quantum wells each having a different spectral peak. In another example, the broad-spectrum laser includes a laser diode emitter with a tunable absorber to achieve a broadened emissions spectrum. In another example, the broad-spectrum laser includes a laser diode emitter array having plural individual emitters with different spectral peaks.

The present disclosure describes broadband optical emission sources that include a stack of semiconductor layers, wherein each of the semiconductor layers is operable to emit light of a different respective wavelength; a light source operable to provide optical pumping for stimulated photon emission from the stack; wherein the semiconductor layers are disposed sequentially in the stack such that a first one of the semiconductor layers is closest to the light source and a last one of the semiconductor layers is furthest from the light source, and wherein each particular one of the semiconductor layers is at least partially transparent to the light generated by the other semiconductor layers that are closer to the light source than the particular semiconductor layer. The disclosure also describes various spectrometers that include a broadband optical emission device, and optionally include a tuneable wavelength filter operable to allow a selected pass through.

The present disclosure discloses a narrow-linewidth laser. The narrow-linewidth laser comprises a passive ring waveguide, a first passive input/output waveguide which is coupled with the passive ring waveguide, a gain wavelength-selection unit which is used for providing gain for the whole laser and is configured to be capable of selecting the light with a specific wavelength to be coupled into the passive ring waveguide, and a second passive input/output waveguide which is coupled with the passive ring waveguide in order to output lasing light from the laser. The narrow-linewidth semiconductor laser provided by the present disclosure has a simple structure and does not have butt-joint coupling loss between a gain region and a waveguide external cavity region. There is no a linewidth limitation caused by butt-coupling loss in such semiconductor lasers. Moreover, because of the integral formation semiconductor technique, the laser should have low cost, higher stability and reliability, and higher resistance to severe environment. Furthermore, based on a loss compensation structure, a ring external cavity of the laser can work in a critical coupling state under different coupling coefficients. Therefore, the laser with a narrow linewidth and a high side-mode suppression ratio should be achieved.

A semiconductor laser tuned with an acousto-optic modulator. The acousto-optic modulator may generate standing waves or traveling waves. When traveling waves are used, a second acousto-optic modulator may be used in a reverse orientation to cancel out a chirp created in the first acousto-optic modulator. The acousto-optic modulator may be used with standing-wave laser resonators or ring lasers.

A quantum cascade laser includes a laser structure having an output face for emitting laser light in a first direction, and a reflecting film provided on the output face. The laser structure includes a core layer. The output face includes an end face of the core layer. The end face includes a first region and a second region that differs from the first region. The reflecting film covers the first region and does not cover the second region.

This oscillator comprises: a source generating an incident optical wave at a pulsation frequency ; an optomechanical resonator, having optical resonances at the pulsation frequency and mechanical resonances at a frequency f.sub.1 and generating, from the incident optical wave, emergent optical waves at the pulsation frequencies and 2f.sub.1, and an acoustic wave at frequency f.sub.1; and, a photodiode delivering a useful signal at frequency f.sub.1 from the emergent waves. This oscillator further comprises: an acoustic propagation means for propagating the acoustic wave over a distance in order to produce a delayed acoustic wave; a means for converting the delayed acoustic wave into a delay signal at the frequency f.sub.1; and, a control loop, processing the delay signal in order to obtain a control signal applied to the source.

A monolithic integrated semiconductor random laser comprising substrate, lower confinement layer on the substrate, active layer on the lower confinement layer, upper confinement layer on the active layer, strip-shaped waveguide layer longitudinally made in middle of the upper confinement layer, P.sup.+ electrode layer divided into two segments and made on the waveguide layer and N.sup.+ electrode layer on a back face of the lower confinement layer, wherein the two segments correspond respectively to gain region and random feedback region. The random feedback region uses a doped waveguide to randomly feedback light emitted by the gain region and then generates random laser which is random in frequency and intensity. Further, the semiconductor laser is light, small, stable in performance and strong in integration.

A photoacoustic apparatus including circuitry configured to generate a frequency comb of light including a plurality of wavelengths; circuitry configured to modulate the light of the frequency comb at a modulation frequency; circuitry configured to change at least a subset of the plurality of wavelengths of the frequency comb of light; and at least one acoustic sensor configured to detect sound produced by analyte illuminated by the frequency comb of light.