A control device for controlling a temperature of a laser device includes a pulse width modulation (PWM) signal generator, a temperature acquisition circuit, a voltage comparator, and a logic circuit. The a pulse width modulation (PWM) signal generator configured to generate a PWM signal; a temperature acquisition circuit configured to acquire a temperature of the laser device and convert the temperature into a measurement voltage; a voltage comparator configured to compare the acquired measurement voltage associated with the temperature of the laser device with a temperature threshold voltage and output a comparison result signal; and a logic circuit configured to generate a drive signal based on the PWM signal and the comparison result signal to drive the laser device.

A light source control device, includes circuitry to: apply a threshold current, a first emission current, and a first correction current to a light source to drive the light source to emit light to form a first pixel, and apply the threshold current, a second emission current, and a second correction current to the light source to drive the light source to emit light to form a second pixel, wherein the circuitry calculates a value of the second correction current by multiplying a value of the first correction current by a ratio of a value of the second emission current to a value of the first emission current, the value of the second emission current being greater than the value of the first emission current.

Apparatuses, methods, and systems are disclosed to drive pumping laser diode arrays. In implementations, an integrated system can be constructed to in a compact, efficient and cost-effective manner and to meet the needs of driving laser diode arrays in various diode pumped solid state laser applications. The disclosed implementations include individual laser diode drivers or pulsers, methods of communicating with laser diode drivers, and methods of controlling the pulse shape of each laser diode driver.

A laser diode control circuit includes: a LD driver circuit for driving a laser diode; a direct current component remover circuit for generating a feedback signal based on a detected signal; a first conversion and filter circuit for generating a first filtered signal based on the feedback signal; a first rectifier for rectifying the first filtered signal to generate a first rectified signal; a reference signal generator for generating a reference signal; a second conversion and filter circuit for generating a second filtered signal based on the reference signal; a second rectifier for rectifying the second filtered signal to generate a second rectified signal; a rectified signals processing circuit for generating a processed signal based on the first and second rectified signals; and a comparator for generating a comparison signal based on the processed signal.

A system comprising drive circuitry configured to apply in a start-up phase a first drive current and then a second different drive current to a laser diode, the first drive current and second drive current being such that the laser diode is configured to provide a first optical output and a second optical output respectively. The system further comprising an optical sensor configured to provide a first sensor output corresponding to the first optical output of the laser diode and a second sensor output corresponding to the second optical output. The system further comprises a controller configured to use a value of the first drive current, a value of the second drive current, the first sensor output, the second sensor output and at least one supplied input value to provide control values for the drive circuitry to control an operating current of the laser diode, wherein the system is arranged to be used in a communication system wherein information is transmitted in at least one burst.

An optical scanning device includes a laser light emitter in which an excess of a current over a bias current is increased or decreased in proportion to an analog signal input thereto, a laser driver to drive the laser light emitter, an optical scanner to scan a surface of an object with laser light emitted from the laser light emitter, an offset value determiner to determine an offset value of the analog signal input to the laser light emitter based on a target light quantity of the laser light emitter, and a laser driver controller to control a quantity of light emitted from the laser light emitter by inputting a signal on the basis of a signal of the determined offset value to the laser driver.

The semiconductor laser driving circuit that controls an overshoot on modulation includes a semiconductor laser, of which anode is connected to a power source, that emits the laser light that is modulated by an external modulation input signal, an impedance element connected to a cathode of the laser device, an impedance element connected to the anode, and a collector of a transistor Q1, connected to the impedance element; a collector of a transistor Q2, connected to the other end of the impedance element, a differential pair circuit to which emitters of Q1, Q2 are connected; an electric current source iMOD connected to the emitters of Q1, Q2; and a differential driver that generates a differential voltage (vb1vb2) that controls Q1, Q2 by driving Q1 by the external modulation input signal, wherein the differential driver controls the differential voltage so that the amplitude of the overshoot of the electric current, which flows in the laser when the output of the laser is at a high-level.

A laser device suppresses the variation of each time-lag so that a distortion of a combined laser output is suppressed. The laser device includes electric current control elements Q1, Q2 connected in series to a laser diode unit corresponding to respective laser diode units LD1, LD2, an electric current control circuit 11 that controls an electric current flow in the laser diode unit by adding a voltage to a control terminal of the electric current control element to turn on the electric current control element, and voltage adjustment circuits 12a, 12b corresponding to the laser diode unit adjusts, individually, every laser diode unit and the voltage that is added to the control terminal of the electric current control element when the laser diode is off.

A method for detecting abnormality in a light emitting device including a semiconductor laser element that is pulse-driven by pulse-control to emit excitation light, a wavelength conversion member including a phosphor and that emits fluorescent light by being irradiated with the excitation light, and a light receiving element disposed on a light extraction side of the wavelength conversion member and that detects the excitation light, the method includes: pulse-controlling an applied voltage with a pulse width shorter than a time from a start of voltage application until an optical intensity of light extracted from the wavelength conversion member reaches a maximum intensity, thereby pulse-driving the semiconductor laser element to achieve laser oscillation; measuring an optical intensity of the excitation light, or optical intensities of both the excitation light and the fluorescent light; and determining whether or not the optical intensity or the optical intensities falls within a prescribed range.

A configuration of a DFB laser-based wavelength tunable laser is well known, but long resonators have difficulty in forming uniform resonators due to production variations, thereby inducing limitation in narrowing the spectral linewidth in the DFB laser-based wavelength tunable laser as well. In the semiconductor laser device of the present invention, a semiconductor laser that oscillates in a single mode and a low-loss lightwave circuit using SiO.sub.2 glass are arranged on the common substrate. The lightwave circuit is configured such that part of output light from the semiconductor laser propagates through a certain length of an optical path, and then is reflected by a reflector and is fed back to the semiconductor laser. Output light from the semiconductor laser and an input waveguide of the lightwave circuit can also be configured to be optically connected directly to each other. The present invention can provide a compact laser device with a narrowed spectral linewidth and stable wavelength controllability.