Abstract: A photodetector and a method of manufacture therefor. The photodetector includes a waveguide located over a photodetector substrate and a resonant coupler located over and coupled to the waveguide. An index of refraction of the resonant coupler is greater than an index of refraction of the waveguide. The photodetector also includes an absorber located over and coupled to the resonant coupler, wherein the absorber has an index of refraction greater than the index of refraction of the resonant coupler.

Abstract: Si-based photodetectors according to the invention can have high speed (e.g.,.gtoreq.1 Gb/s) and high efficiency (e.g.,>20%). The detectors include a relatively thin (e.g.,<0.5.alpha..sup.-1, where .alpha..sup.-1 is the absorption length in Si of the relevant radiation) crystalline Si layer on a dielectric (typically SiO.sub.2) layer, with appropriate contacts on the Si layer. Significantly, the surface of the Si layer is textured such that the radiation that is incident on the surface and transmitted into the Si layer has substantially random direction. The randomization of the propagation direction results in substantial trapping of the radiation in the Si layer, with attendant increased effective propagation length in the Si. Detectors according to the invention advantageously are integrated with the associated circuitry on a Si chip, typically forming an array of detectors.

Abstract: Quantum well infrared photodetectors (QWIPs) according to the invention have a surface that provides pseudo-random reflection of the radiation that is incident thereon, resulting in an increase in the effective number of passes of the radiation through the quantum well region, and hence in increased responsivity of the QWIPs, as compared to corresponding prior art grating QWIPs. A convenient approach to forming the pseudo-random reflecting surface is disclosed.

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 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.