Abstract: An optical gain medium comprising, for example, an optical semiconductor device which is differentially pumped and a master oscillator power amplifier (MOPA) device employing such an amplifier. The gain medium may have a linear stripe region or a diverging stripe region that allows the light propagating therein to diverge along at least part of its length, such as a flared or tapered amplifier having a gain region that increases in width toward its output at a rate that equals or exceeds the divergence of the light. The amplifier is pumped with a current density at its input end which is smaller than the current density used to pump the output end for maintaining coherence of the beam to high power levels employing differential pumping.

Abstract: An optical amplifier semiconductor device which is differentially pumped and a master oscillator power amplifier (MOPA) device employing such an amplifier. The amplifier allows the light propagating therein to diverge along at least part of its length, and may be a flared amplifier having a gain region that increases in width toward its output at a rate that equals or exceeds the divergence of the light. The amplifier is pumped with a current density at its input end which is smaller than the current density used to pump the output end for maintaining coherence of the beam to high power levels. Differential pumping may be both longitudinal and lateral within the amplifier. A single mode preamplifier section may be optically coupled to the input end of the amplifier. The amplifier input may have a width which is the same as or wider than that of the preamplifier output. The preamplifier may have a constant mode width or may be tapered to alter the divergence of the beams provided to the amplifier section.

Abstract: An optical crossbar switch matrix for use in switching optical signals from a first set of optical fibers to a second set of optical fibers, in any order, which is characterized by having a matrix of rows and columns of diffraction gratings formed in a semiconductor heterostructure. Each grating is independently biased with either a forward or reverse bias voltage to switch the grating between a reflective state and a transmissive state. The gratings are oriented at an angle relative to the rows and columns so that when the Bragg condition for the light received from an optical film is met, a portion of the light is diffracted from the row in which it is propagating into a column toward another optical fiber. The heterostructure may include optical amplifiers to restore the optical signal to its original power level. Beam expanding, collimating and focussing optics may also be integrated into the heterostructure.

Abstract: A semiconductor laser that includes at least one grating reflector with a grating period selected to diffract at a nonperpendicular angle within the plane of the laser waveguide. This allows dispersal of laser light, eliminating filamentary multimode operation of broad area lasers. In one embodiment, the grating reflector couples light between a single transverse mode waveguide portion of the optical cavity and a second, broad area, portion that is not collinear with the single mode waveguide. In another embodiment, the cavity favors a ring mode of oscillation. One or more grating reflectors form part of the feedback mechanism which forms a resonant optical cavity with noncollinear portions. Other reflectors in the feedback mechanism include facet reflectors which can be cleaved or ion milled, or semiconductor material refractive index boundaries. Laser embodiments with two or more grating reflectors can be independently tuned to provide a high rate of amplitude modulation.

Abstract: In a semiconductor laser array structure in which antiguided regions between high effective refractive index waveguide regions experience greater gain then the waveguide regions, structures introduced at the sides of the array, next to the edgemost waveguides and not on the array period, reflect laterally transmitted radiation back toward the center of the array. The edge reflecting structures may be waveguide regions having widths of (m'+1/2) half-wavelengths, where "m'" is zero or a positive integer, compared to array waveguides with width m, where "m" is an integer not necessarily equal to "m'". The edge reflecting structures may also be stacks of such waveguides, where the regions between the edge waveguides are of a width substantially equal to (n'+1/2) half-wavelengths, compared to antiguide element widths of n half-wavelengths. The two integers n and n' may be, but are not necessarily, equal.