Abstract: A mode controlling device for capturing a highly divergent, multi-mode laser beam received from a high-power broad area laser source and producing a narrow, single-mode laser beam. In one embodiment, the mode controlling device comprises a diffractive device having a nonplanar profile positioned to receive the multi-mode laser beam. The diffractive device comprises a plurality of grooves for receiving the multi-mode laser beam and diffracting light to a reflective medium, thereby creating feedback for producing a narrow, single-mode laser beam with a non-uniform intensity profile. The reflective medium may be positioned at the surface of the diffractive device; alternatively, the reflective medium may be positioned at a predetermined distance from the diffractive device.

Abstract: A mode controlling device for capturing a highly divergent, multi-mode laser beam received from a high-power broad area laser source and producing a narrow, single-mode laser beam. In one embodiment, the mode controlling device comprises a diffractive device having a nonplanar profile positioned to receive the multi-mode laser beam. The diffractive device comprises a plurality of grooves for receiving the multi-mode laser beam and diffracting light to a reflective medium, thereby creating feedback for producing a narrow, single-mode laser beam with a non-uniform intensity profile. The reflective medium may be positioned at the surface of the diffractive device; alternatively, the reflective medium may be positioned at a predetermined distance from the diffractive device.

Abstract: A device for generating blue or green laser light by the use of a device comprising an infrared high power semiconductor laser or an infrared high power semiconductor laser bar or array, a diffractive optical device, and an optical device utilizing a non-linear crystal to generate the blue or green laser light. In one embodiment, the diffractive optical device comprises a volume holographic transmission grating and the optical device comprises a ring resonator. In another embodiment, the diffractive optical device comprises a reflective diffraction grating feedback mechanism and the optical device comprises a ring resonator. In another embodiment, the optical device comprises a parabolic or non-planar feedback mechanism and a ring resonator. In another embodiment, the diffractive optical feedback device, which can be in the form of digital/binary optics, is attached to the semiconductor laser source.

Abstract: A semi-conductor device having the properties of carrier confinement induced by local variations of strain comprising a semi-conductor base material, a vertical confinement layer over the semi-conductor base material for vertical confining charge carriers and a strain layer which creates a local strain pattern in the underlying semi-conductor material which strain pattern laterally confines charge carriers in accordance with the strain pattern. The semi-conductor base may include a quantum-well, e.g., one formed utilizing a superlattice structure, where the charge carriers are laterally confined within the quantum well by the strain pattern.

Abstract: A low noise multistage photodetector device is formed from a sequence of pairs of layers of opposite conductivity type having heterojunctions between each pair. The second layer of each pair has a bandgap which is larger than the bandgap of the first layer of the pair adjacent to the second layer. Electrodes are formed on the device so that voltages may be applied to reverse bias the heterojunctions formed between each pair in the sequence and to forward bias the heterojunctions formed between the second layer of one pair and the first layer of another pair. The device provides traps for one sign of carrier, which traps prevent the trapped carrier from avalanching through amplification regions of the device.

Abstract: Devices constructed according to the present invention provide low noise avalanche photodetectors. The devices are comprised of a sequence of at least four layers of semiconductor material of alternating opposed conductivity. In a first embodiment the layers form alternating homojunctions and heterojunctions at the interface between adjacent layers, and the bandgap of the layers on either side of the homojunctions decreases in the direction of the propagating signal. In another embodiment the layers form heterojunctions at the interfaces between adjacent layers; the layers are grouped into a sequence of pairs of layers where the bandgap of the two layers in each pair are substantially equal; and the bandgap of the layers in the sequence of pairs of layers decreases in the direction of the propagating signal. The effect of the structure of the multilayer device is to create traps for one sign of carrier and to prevent the trapped carrier from avalanching through amplification regions of the device.