Disclosed is a terahertz wave generating apparatus. The terahertz wave generating apparatus includes a dual mode laser including a first single mode laser that generates a first beating signal, a gain adjustment region that modulates the first beating signal, and a second single mode laser that generates a second beating signal, and a photomixer that mixes the modulated first beating signal and the second beating signal, and that modulates a current supplied based on a beating frequency of the mixed beating signals to generate a terahertz wave signal, and the gain adjustment region is formed between the first single mode laser and the second single mode laser, and the first beating signal is output from the first single mode laser to the gain adjustment region and is modulated based on a reverse bias voltage supplied to the gain adjustment region.

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 embodiment relates to a light emitting device having a structure capable of removing zero order light from output light of an S-iPM laser. The light emitting device includes a semiconductor light emitting element and a light shielding member. The semiconductor light emitting element includes an active layer, a pair of cladding layers, and a phase modulation layer. The phase modulation layer has a basic layer and a plurality of modified refractive index regions, each of which is individually disposed at a specific position. The light shielding member has a function of passing through a specific optical image output along an inclined direction and shielding zero order light output along a normal direction of a light emitting surface.

The present embodiment relates to a light emitting device having a structure capable of removing zero order light from output light of an S-iPM laser. The light emitting device includes a semiconductor light emitting element and a light shielding member. The semiconductor light emitting element includes an active layer, a pair of cladding layers, and a phase modulation layer. The phase modulation layer has a basic layer and a plurality of modified refractive index regions, each of which is individually disposed at a specific position. The light shielding member has a function of passing through a specific optical image output along an inclined direction and shielding zero order light output along a normal direction of a light emitting surface.

A electro-absorption optical modulator includes a multiple quantum well composed of a plurality of layers including a plurality of quantum well layers and a plurality of barrier layers that are alternately stacked, the plurality of quantum well layers and the plurality of barrier layers including an acceptor and a donor; a p-type semiconductor layer in contact with an uppermost layer of the plurality of layers; and an n-type semiconductor layer in contact with a lowermost layer of the plurality of layers, the multiple quantum well being 10% or more and 150% or less of the p-type semiconductor layer in a p-type carrier concentration, and in the multiple quantum well, an effective carrier concentration which corresponds to a difference between the p-type carrier concentration and an n-type carrier concentration is 10% or less of the p-type carrier concentration of the multiple quantum well.

A limited range source of electromagnetic radiation and a radiation method, includes a tunable source of electromagnetic radiation; and a control element configured to tune the wavelength of the source of electromagnetic radiation to a desired wavelength corresponding to an absorption line of an atom or a molecule or other species present in the medium through which the electromagnetic radiation is to propagate; wherein the control element is configured to receive data relating to the desired wavelength.

Examples disclosed herein relate to multi-wavelength semiconductor lasers. In some examples disclosed herein, a multi-wavelength semiconductor laser may include a silicon-on-insulator (SOI) substrate and a quantum dot (QD) layer above the SOI substrate. The QD layer may include and active gain region and may have at least one angled junction at one end of the QD layer. The SOI substrate may include a waveguide in an upper silicon layer and a mode converter to facilitate optical coupling of a lasing mode to the waveguide.

There is disclosed a DBR laser and a method of use. The DBR laser comprises a phase section in a cavity of the DBR laser and configured to adjust an optical path length of the cavity. A DBR section comprises a frequency tuning system configured to adjust a Bragg frequency of the DBR section. A detector is configured to detect laser light transmitted through the DBR section. A controller is configured: to cause the phase section to apply a dither to the optical path length of the cavity or cause the frequency tuning system to apply a dither to the Bragg frequency of the DBR section; to use the detector to monitor intensity of light transmitted from the laser cavity via the DBR section during application of the dither; to determine a deviation from longitudinal mode centre operation on the basis of the monitored intensity; and to cause the frequency tuning system to adjust the Bragg frequency of the DBR section in order to reduce said deviation, or cause the phase section to adjust the optical path length of the cavity in order to reduce said deviation.

A vertical cavity surface emitting laser (VCSEL) has first and second electrical contacts, and an optical resonator. The optical resonator has first and second distributed Bragg reflectors (DBRs), an active layer, a distributed heterojunction bipolar phototransistor (DHBP), and an optical guide. The DHBP has a collector layer, light sensitive layer; a base layer; and an emitter layer. There is an optical coupling between the active layer and the DHBP for providing an active carrier confinement by the DHBP. The optical guide guides an optical mode within the optical resonator during operation. The optical guide is outside a current flow which can be provided by the first and second electrical contacts during operation of the VCSEL. The optical guide is outside a layer sequence between the first and second electrical contacts in the vertical direction of the VCSEL. The optical guide has an oxide aperture arranged in the second DBR.