A method for physical random number generation includes the steps of: modulating the gain of a vertical-cavity surface-emitting laser periodically from the lower threshold to the upper threshold and back; maintaining the gain per round trip positive for a longer period than the round trip time of the cavity; maintaining the net gain per round trip negative for a longer period than the round trip time of the cavity, in order to create optical pulses of random amplitude; detecting the optical pulses; converting the optical pulses into electrical analog pulses; and digitising the electrical analog pulses into random numbers.

An optical device comprises a light input, a light modulating means and a light output. The optical device further comprises an optical amplification device arranged to amplify light travelling between said light modulating means and said output. The optical amplification device comprises first and second serially connected post SOA (Semiconductor Optical Amplifier) units, each comprising at least one respective serially connected post SOA segment, which device is arranged to vary a light amplification by varying respective SOA bias voltages across said post SOA segments. A total SOA length of the first post SOA unit is relatively longer than a total SOA length of the second post SOA unit, which is relatively shorter. The optical device is arranged to, during operation using a particular operation program, always keep respective SOA bias voltages across each of the post SOA segments of the first post SOA unit at +0.5 V or more.

A header for a semiconductor package, includes an eyelet having an upper surface, and a lower surface on an opposite side from the upper surface, a metal block having a side surface, and configured to protrude from the upper surface of the eyelet, a lead sealed in a through hole which penetrates the eyelet from the upper surface to the lower surface of the eyelet, and a substrate having a front surface formed with a signal pattern electrically connected to the lead, and a back surface on an opposite side from the front surface. The back surface of the substrate is fixed to the side surface of the metal block. A portion of the back surface of the substrate is exposed from the metal block, and this portion of the substrate is formed with a ground pattern.

A laser apparatus includes: a light source configured to generate laser light; and an optical negative feedback unit configured to narrow a spectral line of the laser light using optical negative feedback. A modulation signal is input to the light source to modulate a frequency of the laser light. A modulation amount in the frequency of the laser light is detected. A modulation sensitivity is calculated from (i) the modulation amount and (ii) an intensity of the modulation signal.

A laser system is provided that includes a modulated laser, which is configured to generate an amplitude modulated laser signal, comprising a first amplitude modulation. The first amplitude modulation is based on a data signal. Moreover, the laser system includes an optical modulator, which is configured to receive the amplitude modulated laser signal as an input signal, and modulate the amplitude modulated laser signal with a second amplitude modulation, based on the data signal, resulting in an amplitude modulated output laser signal.

Method and gas analyzer for measuring the concentration of a gas component in a measurement gas, a wavelength-tunable laser diode is actuated with a current, one part of the light generated by the laser diode is guided through the measurement gas to a measuring detector to generate a measuring signal, the other part of the light is guided to a monitor detector to generate a monitor signal, the current is varied in periodically consecutive scanning intervals to scan an absorption line of interest of the gas component as a function of the wavelength, the current is further modulated with a radio-frequency noise signal having a lower cut-off frequency selected as a function of the properties of the laser diode and high enough to ensure no wavelength modulation occurs and the measuring signal is correlated with the monitor signal and then evaluated to generate a measurement result.

A Lidar system includes a tunable laser configured to generate an output light signal and a photodiode array for receiving light from the tunable laser reflected from a target object. The tunable laser includes a feedback loop including a Mach-Zender interferometer, MZI, receiving the output light signal from the tunable laser, in which the MZI includes two optical paths receiving the output light signal. A phase shifter is provided in one optical path that is operable to produce a pre-determined shift in the phase angle of the light signal passing through the one optical path relative to the phase angle of the light signal passing through the other optical path. A photodiode configured to detect the interference signal generated by the MZI is operable to generate a photodiode current in response thereto. Circuitry converts the photodiode current to a control signal for controlling the tunable laser.

A CMOS inverter circuit is provided as a circuit to modulate a current flowing into a laser diode on the basis of a digital signal. An amplitude of a current flowing in a PMOSFET in the CMOS inverter circuit is made to contribute to an amplitude of the current flowing into the laser diode, to reduce an input amplitude.

A narrow linewidth external cavity laser includes a sealed housing, an external resonant cavity disposed in the sealed housing, and a gain chip and a tunable wavelength selective component disposed in the external resonant cavity. An electrical interface of the sealed housing is configured to receive an electrical signal such as a drive signal, a wave selection signal, a cavity length control signal, and a dither control signal. The cavity length control signal is configured to adjust an optical cavity length of the external resonant cavity so that a laser mode produced in the external resonant cavity aligns with a wavelength selected by the wavelength selective component. The dither control signal is configured to control the optical cavity length of the external resonant cavity to produce dither by adjusting an optical length of the gain chip in order to lock a center wavelength of an output light beam.

In a drive unit according to an embodiment of the present disclosure, in each of a plurality of current pulses, a rising crest value is the largest, and after the rising, the crest value is damped. Further, a rising crest value of a pulse of an n+1-th wave is smaller than a rising crest value of a pulse of an n-th wave. Furthermore, rising crest values of the current pulses of a second wave and waves after the second wave are determined by a mathematical function expressed as an electric potential change caused by ON-OFF of an RC time constant circuit that is single-end grounded. Moreover, in the mathematical function, a time constant at an OFF time is larger than a time constant at an ON time.