Abstract: In accordance with the present invention, a surface emitting laser includes a substrate, a first distributed feedback mirror formed on the substrate, and an active gain medium formed on the first mirror. The active gain medium includes at least one active, optically emitting layer and one barrier layer. A second distributed feedback mirror is formed on the active gain medium. The first and second mirrors define a resonant cavity for supporting a standing wave optical field at a designed wavelength of operation The first and second mirrors have first and second reflective bandwidths that respectively include first and second transmissive bandwidths for receiving optical pumping energy. The first and second reflective bandwidths are shifted in wavelength relative to one another so that the first and second transmissive bandwidths are located at distinct wavelengths.

Abstract: A read/write system which reduces access time in optical disc apparatus is disclosed. The head includes an array of lenses which covers a substantial portion of the radius of the disc. Access of a particular disc track is achieved by deflection of the reading beam, rather than by any physical movement of the head. For read-out, the array focuses light reflected from the disc onto a corresponding array of photodetectors.

Abstract: A semiconductor apparatus is provided. The apparatus has a multiple layer heterostructure having first and second material layers having first and second bandgaps, respectively and a semiconductor layer of a third bandgap being fabricated between said material layers, the bottom of the conduction band of said semiconductor layer is below the bottom of the conduction band of said material layers, and the top of the valence band of said semiconductor layer is above the top of the valence band of said material layers, the thickness of said semiconductor layer is chosen sufficient for carrier confinement effects within said semiconductor layer to influence the optical properties of said multiple layer heterostructure, and means for applying an electric field to the multiple layer heterostructure in order to vary an optical absorption coefficient and an index of refraction of the multiple layer heterostructure in response to the electric field.

Abstract: Tunable laser radiation is obtained by pumping a wedge-shaped ultra-short laser cavity with picosecond excitation pulses. Continuous tuning of the laser is achieved by translating either the wedge-shaped laser cavity or the excitation pulses so that different volumes of the laser material are exposed to the excitation pulses. In one embodiment utilizing picosecond laser excitation pulses the wedge-shaped laser cavity is a slightly wedged film of GaAs coated on both sides with dielectric mirrors.

Abstract: Broadband laser gain is obtained in semiconductor materials by pumping an ultra-short laser cavity with picosecond excitation pulses. The broadband laser gain is used to provide picosecond laser radiation energy covering a wide spectrum of frequencies.

Abstract: A tunable far infrared generator makes use of a four-photon mixing process that cycles among highly excited atomic states, the lowest of which states is reached from the atomic ground state by a visible or ultraviolet photon, and the remainder of which states are connected by transitions in the infrared.