One aspect provides a method for providing a short electrical pulse using a switching circuit, the method including: providing a forward current to at least one semiconductor diode electrically connected with and controlling electrical current to an electrical component within a circuit; and switching the at least one semiconductor diode into a reverse bias by applying a reverse voltage to the at least one semiconductor diode, thereby causing the at least one semiconductor diode to enter a reverse recovery state and controlling a destination of the electrical current and generating the short electrical pulse to the destination for the duration of the reverse recovery state; the duration of the reverse recovery state being based upon a value of the forward current and a value of the reverse voltage.

A semiconductor laser is provided with: an active layer that excites a transverse electric (TE) mode and a transverse magnetic (TM) mode of light and constitutes at least a part of a resonator guiding the TE mode and the TM mode of light; and a diffraction grating as a frequency difference setting structure that sets the difference in oscillation frequency between the TE mode and the TM mode of light higher than a relaxation-oscillation frequency.

A semiconductor device includes an electrode which is arranged on an organic material with an insulation film interposed therebetween and which does not easily peel away from the organic material along with the insulation film. An insulation film in a region including pad portions of a phase shift electrode and a modulation electrode has openings at the centers of the pad portions of the phase shift electrode and the modulation electrode, the edge portions of which are formed on the phase shift electrode and the modulation electrode. In this way, the adjoining edges of the phase shift electrode and modulation electrode and the insulation film are all covered by the insulation film so as not to be exposed to the atmosphere. By covering the cracks that occur in the insulation film in the production process with the insulation film made of SiO.sub.2, SiN.sub.X, SiON.sub.X or the like, an organic solvent such as acetone or ethanol used in the process can be prevented from seeping in between the insulation film and the organic material through the cracks in the insulation film.

An optical device for a quantum random number generator comprising: a source of phase randomised pulses of light, the source of phase randomised pulses of light further comprising a plurality of gain-switched lasers, each gain-switched laser having an output, and each gain-switched laser being configured to emit a stream of pulses such that the phase of each pulse in the stream of pulses is randomised, and an optical pulse combiner, the optical pulse combiner being configured to receive streams of pulses from the output of each gain-switched laser, combine the streams of pulses with one another into a combined stream of pulses and direct the combined stream of pulses into at least one output of the optical pulse combiner, the at least one output of the optical pulse combiner being the output of the source of phase randomised pulses of light; wherein the source of phase randomised pulses of light is configured such that the streams of pulses of light emitted by the plurality of gain-switched lasers are temporally offset relative to one another, a phase measurement element, the phase measurement element being configured to receive the combined stream of pulses from the output of the source of phase randomised pulses of light; and an optical detector, the optical detector being optically coupled to the phase measurement element.

A laser light source may include an arrangement of surface-emitting semiconductor lasers to which a voltage is applied such that an operating current is below the threshold current and an intrinsic emission of the surface-emitting semiconductor laser is prevented. The laser light source also comprises a first semiconductor laser which emits radiation that enters the surface-emitting semiconductor laser such that induced emission takes place via the injection locking mechanism and the individual surface-emitting semiconductor lasers emit laser light having the same wavelength and polarisation direction as the irradiated radiation. The emission frequency of the first semiconductor laser can be changed by changing the operating current.

Example vertical cavity surface emitting lasers (VCSELs) include a mesa structure disposed on a substrate, the mesa structure including a first reflector, a second reflector defining at least one diameter, and an active cavity material structure disposed between the first and second reflectors; and a second contact layer disposed at least in part on top of the mesa structure and defining a physical emission aperture having a physical emission aperture diameter. The ratio of the physical emission aperture diameter to the at least one diameter is greater than or approximately 0.172 and/or the ratio of the physical emission aperture diameter to the at least one diameter is less than or approximately 0.36. An example VCSEL includes a substrate; a buffer layer disposed on a portion of the substrate; and an emission structure disposed on the buffer layer.

A metal stem includes a cylindrical portion in which an FPC inserting portion is formed, and a base standing upright from one plane of the cylindrical portion. A tubular lens cap with one open end is fixed to a peripheral portion of the one plane of the cylindrical portion, and has a lens mounted on a bottomed portion. A substrate mounted on one plane of the base includes a signal wiring layer and a ground wiring layer. An optical semiconductor element is mounted on the substrate and has a signal terminal connected to the signal wiring layer of the substrate, and a ground terminal connected to the ground wiring layer of the substrate. An FPC substrate is disposed so as to pass through the FPC inserting portion and to face the one plane of the base. The FPC substrate includes a signal wiring layer connected to the signal wiring layer of the substrate with a metal wire.

A 2nd signal line has impedance lower than impedance of a 1st signal line. A capacitor includes a 1st extension part and a 2nd extension part, a 1st ground part and a 2nd ground part. The 1st extension part and the 2nd extension part are connected to a 2nd signal line and are provided on an insulation substrate to extend along a longitudinal direction of the 2nd signal line. The 1st ground part and the 2nd ground part are at least a part of a ground pattern, and are provided between the 1st extension part and the 2nd extension part and the 2nd signal line, and between the 1st extension part and the 2nd extension part and an end part of the insulation substrate, to be electrically coupled with the 1st extension part and the 2nd extension part.

A light-emitting device includes a light emission section (Em), a separation groove (152), and a high reflectance region (Hr). The light emission section (Em) includes a stack structure (100) including an active layer (100), a first reflector (110), and a second reflector (120). The active layer (130) performs light emission by current injection. The first reflector (110) and the second reflector (120) are stacked in a first direction with the active layer (130) interposed therebetween. The separation groove (152) is provided symmetrically around the light emission section (Em) on an emission surface of light from the stack structure (100) in the first direction. The separation groove (152) is dug in the stack structure (100) in the first direction. The high resistance region (Hr) is provided in the stack structure (100) on the outer side of an outermost shape of the separation groove (152) on the emission surface. The high resistance region (Hr) has electrical resistance higher than that of the light emission section (Em).

A controller stabilizes a distributed feedback plus reflection (DFB+R) laser, which has a back facet, a DFB section, a passive section, and a front facet with a low reflective element. An etalon filter is formed by a portion of the DFB section, the passive section, and the low reflective element. Control circuitry directly modulates the DFB section with a modulation signal and biases the passive section with a bias signal. In operation, a lasing mode of the DFB section is aligned to a long wavelength edge of one of the periodic peaks of a reflection profile of the etalon filter. Meanwhile, photodiodes are arranged to monitor the output power emitted from the laser's front and back facets. The control circuitry monitors a ratio of the detected output power and adjusts the bias based on the monitored ratio.