Abstract: A superimposed grating tunable WDM semiconductor laser is provided comprising a grating structure is a binary superimposed grating comprising a plurality of segments of equal dimension, s, each segment having one of two values of refractive index, whereby the grating structure is provided by a binary modulation of the refractive index modulation of segments s along the length of the grating.Thus, for a superimposed grating structure for an optoelectronic device for providing a spectrum comprising j reflection peaks at wavelengths .lambda..sub.j, the grating comprising a binary superimposed grating (BSG) having a sequence of a plurality of segments of equal size s, each segment of the sequence having a refractive index of one of two values wherein the effective waveguide index of the ith segment n.sub.i.sup.0 (.lambda.) is allowed to be changed by .DELTA.n.multidot.(m-1/2) with m=1 or m=0: ##EQU1## where i=1,2,3 . . . is the segment number, for digital position i.multidot.s, n.sup.0 (.lambda.

Abstract: A complex coupled (gain coupled or loss coupled) distributed feedback (DFB) semiconductor laser, having two sections axially distinct along a cavity length direction, and two excitation means for independent pumping of corresponding sections of the laser in a master and slave type of pumping control, is provided. An extended continuous wavelength tuning range of the laser is obtained by selectively activating a left Bragg mode or a right Bragg mode across the stop band of the laser as a dominant lasing mode by the master and slave type of current injection control into different sections of the laser to alternate gain coupling and loss coupling mechanisms of laser operation, and further tuning a wavelength around the activated Bragg mode. Methods of operating the laser, enhancing a tuning range, and fabricating thereof are provided.

Abstract: A system for generating an ultra short optical pulse by pumping a semiconductor signal laser with an optical pulse from a semiconductor probe laser. The signal laser has dual segments each operated under different d.c. injection current levels. The probe laser is modulated with a pulsed input and the optical output thereof is coupled via optical means to the signal laser so as to Q-switch the latter. Optical pulses in the 65 ps range result.

Abstract: A gain-coupled distributed feedback (DFB) laser or amplifier structure having a gain-coupling grating in the form of grooves periodically etched through strained, multi-quantum wells. The etched grooves are regrown with buffer material having a bandgap selected to compensate for index-coupling aid to block carrier leakage. The low carrier leakage reduces non-radiative recombination which in turn increases quantum efficiency.