Abstract: The inventive methods of making a semiconductor device, e.g., a laser, comprise thermal (e.g., 3-5 .mu.m wavelength) imaging of a powered, partially completed device. The thermal image is obtained with apparatus that is capable of forming a substantially diffraction-limited image on a sensor array with an acquisition time of no more than 0.1 seconds, preferable no more than 0.01 seconds. In preferred embodiments, the image has temperature resolution of 0.01.degree. C. or better. Exemplary apparatus is disclosed. The inventive method facilitates, for instance, early identification of devices that are likely to fail lifetime requirements.

Abstract: Electromagnetic radiation such as, in particular, infrared radiation is detected opto-electronically by means of a superlattice structure forming quantum wells having a single bound state; in the interest of minimizing dark-current, relatively wide barriers are used between quantum wells. Resulting highly sensitive, high-speed detectors can be used in optical communications, for terrain mapping, and for infrared viewing. Furthermore, upon application of a variable electrical potential across the superlattice structure, radiation traversing such structure can be modulated.

Abstract: Radiation-induced effects discovered in layered structures of conductor and semiconductor materials are utilized in radiation-sensitive devices such as, e.g., highly linear as well as highly nonlinear position sensors. Such devices includes a structure of alternating layers of conductor and semiconductor materials, and electrical contacts are provided between which a radiation-induced voltage appears. Among suitable layer materials are silicon and titanium, and resulting devices are sensitive to electromagnetic as well as to particle radiation.

Abstract: A narrow-bandwidth, high-speed infrared radiation detector is based on tunneling of photo-excited electrons out of quantum wells. Infrared radiation incident on a superlattice of doped quantum wells gives rise to intersubband resonance radiation which excites electrons from the ground state into an excited state. A photocurrent results from excited electrons tunneling out of quantum wells. Conveniently, Group III-V materials can be used in device manufacture. Preferably, quantum well potential barriers are shaped so as to facilitate resonant tunneling of photocurrents as compared with dark current. Preferred device operation is at elevated bias voltage, giving rise to enhancement of photocurrent by a quantum-well-avalanche effect.

Abstract: An avalanche photodetector having separate absorption and multiplication regions comprising Group III-V compound semiconductors is useful as a detector of small numbers of photons when it is operated with an above threshold bias voltage at ambient temperature.

Abstract: A modulation-doped field effect photodetector has a fast response time.

Abstract: A photodetector having a graded bandgap region is an ultrahigh speed photodetector when operated at zero bias.

Abstract: Nonlinear devices using 2-methyl-4-nitroaniline are described. Devices using 2-methyl-4-nitroaniline as the active element include second harmonic generators, optical mixers and parametric oscillators which can be operated under phasematched conditions.

Abstract: An optically nonlinear liquid thin film in a thin film optical waveguide is utilized in order to produce optical parametric interactions such as second harmonic generation. Optimization (tuning) of parametric output by "phase matching" is achieved by means of an electric field which is set up in the liquid film, the field having a spatial periodicity along the propagation direction of the optical waves in the thin film. Alternative or further optimization of parametric output is achieved by varying the thickness of the liquid film in situ.