Abstract: An optical transmission system is formed to include an optical phase conjugator at alternate repeater sites to minimize the presence of four-wave mixing and other Kerr effect nonlinearities in systems using optical fiber transmission paths (particularly in systems using DWDM and launching relatively high power signals into the low dispersion fiber). Raman gain is included in each fiber span (or in alternate fiber spans) so as to provide a “negative absorption” along the length of the fiber and thereby provide for essentially symmetrical power distribution along the length of each span, where the presence of such a symmetric,power distribution on each side of an optical phase conjugator has been found to significantly improve its performance.

Abstract: A waveguide structure for use with a pump laser is disclosed that is designed to counteract the decrease in pump power density. The waveguide structure may comprise an erbium-doped waveguide amplifier, a nonlinear waveguide wavelength converter device, or an optical fiber. The waveguide structure has a waveguide region that is tapered over a pump propagation distance, said distance being defined as a predetermined distance between a first pump site and a second pump site over which the pump light is propagated for signal amplification or conversion. The taper reduces the depletion in pump power as compared with prior art systems and may be kept substantially constant over the pump propagation length, thereby counteracting pump depletion.

Abstract: An accurate and simplified method of non-destructively measuring the zero-dispersion wavelength along the length of a single-mode fiber is disclosed. The method includes the steps of measuring the FWM intensity of the optical fiber at a plurality of wavelengths, plotting the measured FWM intensity at each of the plurality of wavelengths to obtain a curve representative of the FWM intensity of each of the plurality of wavelength, and performing a non-linear inversion on the curve to obtain the zero-dispersion wavelength along the length of the fiber.

Abstract: A THz imaging system with the emitter region of the THz generator designed so that the sample to be analyzed is placed in the near field of the generator allows radiation to impact the sample without intervening optics.

Abstract: The specification describes pulse generators and detectors for the far infra-red and operating at frequencies of the order of 10.sup.10 to 10.sup.13 Hz (the Terahertz range). These devices rely on electric field interactions with optical beams in biased metal semiconductor microstructures. The electric field is created between metal electrodes on the semiconductor surface and the electric field is enhanced, according to the invention, by configuring the electrode gap geometry with sharp electrode features.

Abstract: A new method to fabricate strain patterns on a strained semiconductor structure, is disclosed. The method is based on the new concept of reverse side etching of a laterally homogeneous, strained structure so that strain changes can be induced in the front-side, pre-strained area as a result of the reverse side etching process. Semiconductor structures such as quantum-wires, quantum dots, and quantum well devices may be formed by the disclosed methods where the reverse side etching provides strain control of the material properties of the semiconductor structure without processing the front side which is generally the active and the most sensitive region of the semiconductor structure. Such semiconductor structures can be formed by a process including the steps of forming a strained layer on the front-side of the structure, and etching the reverse side of the substrate to form a pattern of strain into the front-side, thus forming selectively strained regions.

Abstract: Apparatus and methods of near-field scanning optical microscopy (NSOM) are described. A sensing technique is used, in which a light source having an optical cavity is reflectively coupled to the sample surface. Changes in the surface properties of the sample at the sensed location alter the optical feedback in the light source. This leads to detectable changes in the output characteristics of the light source.