A semiconductor light emitting device of double hetero junction includes an active layer and clad layers. The clad layers include an n-type layer and p-type layer. The clad layers sandwich the active layer. A band gap energy of the clad layers is larger than that of the active layer. The band gap energy of the n-type clad layer is smaller than of the p-type clad layer.

Semiconductor light emitting device and manufacturing method therefor

A gas discharge laser crystallization apparatus and method for performing a transformation of a crystal makeup or orientation in a film on a workpiece is disclosed, which may comprise a master oscillator power amplifier MOPA or power oscillator power amplifier configured XeF laser system producing a laser output light pulse beam at a high repetition rate and high power with a pulse to pulse dose control; an optical system producing an elongated thin pulsed working beam from the laser output light pulse beam. The apparatus may further comprise the laser system is configured as a POPA laser system and further comprising: relay optics operative to direct a first output laser light pulse beam from a first laser PO unit into a second laser PA unit; and, a timing and control module timing the creation of a gas discharge in the first and second laser units within plus or minus 3 ns, to produce the a second laser output light pulse beam as an amplification of the first laser output light pulse beam. The system may comprise divergence control in the oscillator laser unit. Divergence control may comprise an unstable resonator arrangement. The system may further comprise a beam pointing control mechanism intermediate the laser and the workpiece and a beam position control mechanism intermediate the laser and the workpiece. Beam parameter metrology may provide active feedback control to the beam pointing mechanism and active feedback control to the beam position control mechanism.

Laser thin film poly-silicon annealing system

A semiconductor laser apparatus comprises a light-emitting portion including a light-emitting device for outputting a laser beam, a light-receiving element for receiving the laser beam outputted from said light-emitting device, a wavelength monitoring portion including an optical system disposed between said light-emitting device and said light-receiving element, a control portion for controlling the wavelength of the laser beam outputted from said light-emitting device by controlling the temperature of said light-emitting device based on the wavelength of the laser beam detected by said wavelength monitoring portion, an optical isolator disposed on the optical path between said light-emitting device and said wavelength monitoring portion for preventing the light from returning from said wavelength monitoring portion back to said light-emitting device, and a temperature regulating portion for independently controlling the temperatures of said light-emitting portion and wavelength monitoring portion.

Semiconductor laser apparatus, semiconductor laser module, optical transmitter and wavelength division multiplexing communication system

Accurate and efficient synchronization of two pulsed radiation sources (e.g. iwo mode locked lasers) is accomplished in stages. Rough synchronization is accomplished by synchronizing (for example) the fundamental repetition rate of the two lasers. Fine synchronization is accomplished by synchronizing high harmonics of the two lasers. More accurate synchronization may be accomplished by adding more stages, by utilizing light out of a nonlinear laser in which the two beams are crossed, or by utilizing heterodyne beats of the two laser beams. A dc offset signal may added to the control signal generated by the synchronization stages.

Multistage synchronization of pulsed radiation sources

A VSB generation control system is provided that uses received signal quality (detected error rate) as a measure of correct VSB filter or signal wavelength adjustment. The use of VSB will offer spectral efficiency improvements for optical transmission and the margins gained may be used either to increase span length or reduce wavelength spacing. The control loops proposed offer minimal complexity and implementation whilst providing reliable and understandable performance improvement.

Optical vestigial sideband (VSB) transmission

A multichannel light source wavelength and strength stabilizing apparatus and a method thereof are disclosed. The apparatus includes a first proportional/integrator for receiving an output signal from the error detector, detecting a value proportional thereto, integrating the detected proportional value, generating a signal corresponding to the optimum feedback circuit, and outputting to the temperature controller; a current controller for providing the current capable of controlling the light strength in accordance with the signal inputted to the light source and stabilizing the light strength; a second optical coupling unit for dividing the output signal from the first optical coupling unit; a photodetector for converting the strength of a light among the output signals from the second optical coupling unit into an electrical signal; and a second proportional/integration unit for detecting a proportional value of the output signal from the optical detector, integrating the detected proportional value, generating a signal corresponding to the optimum feedback circuit, and outputting to the current controller.

Multichannel light source wavelength and strength stabilizing apparatus and method thereof

Wavelength and power stabilization apparatus

A fuel cell system and a method of purging the same are provided. The fuel cell system includes: a fuel cell stack that includes a fuel electrode and an air electrode as well as an air supply unit that supplies air of a blower to the air electrode via a humidifier through an air supply line. A water trap collects condensed water that is generated at the fuel electrode, and a drain valve that is installed within a drain line between the water trap and the humidifier is also provided. A purge valve is installed at a purge line that is branched from the drain line between the fuel cell stack and the water trap. in particular, by opening the drain valve and the purge valve during operation, condensed water and unreacted hydrogen are each exhausted to the humidifier, and when operation is terminated, by opening the drain valve, condensed water and unreacted hydrogen are exhausted to the humidifier, and by opening the purge valve in a different flow direction, unreacted hydrogen is purged to the air electrode inlet side.

Fuel cell system and method of purging the same

Provided is a fuel cell system and a purging method thereof. A fuel cell system according to an embodiment of the present invention comprises a stack having a fuel electrode and an air electrode; an air supply for supplying air to the air electrode through an air supply line and a humidifier; a water trap trapping condensed water formed from the fuel electrode; a drain valve installed in a discharge line between the water trap and the humidifier; and a purge valve installed in a purge line, which is branched from a discharge line between the stack and the water trap. In operation, the drain valve and the purge valve are opened to discharge the condensed water and unreactive hydrogen and, at the end of operation, the drain valve is opened to discharge the condensed water and the unreactive hydrogen to the humidifier, and the purge valve is opened to purge the unreactive hydrogen toward the inlet of the air electrode.

Fuel cell system and purging method thereof

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Multichannel light source wavelength and strength stabilizing apparatus and method thereof

Wavelength and power stabilization apparatus

Fuel cell system and method of purging the same

Fuel cell system and purging method thereof