We demonstrate the feasibility of a novel microgun-pumped semiconductor laser. This is the most compact (a few cm3) and the lowest threshold electron-beam-pumped semiconductor laser ever reported. The electron source is provided by a 104–105/mm2 array of field emissive microtip cathodes each of 1.5 μm diam. The laser operates below 10 kV and below 1 A/cm2. Laser action in a quasi-cw mode with 5 μs pulses at 2 kHz has been obtained between 90 and 300 K with CdTe-CdMnTe graded index separate confinement quantum-well heterostructures, as well as with GaAs-GaAlAs structures. Since neither doping nor ohmic contacts are needed, the microgun laser can use all direct gap semiconductors. It appears as a viable solution for making compact II-VI lasers in the visible domain.
An homeotropic cell is built with a thin layer (5–25 μm) of nematic liquid crystal such as MBBA sandwiched between two indium oxide coated glass plates. The transient behavior of the cooperative angular variation of molecules submitted to an electric field step is studied theoretically. Experimental results are obtained by optical detection of the birefringence variations in the cell. Comparison of these studies allows one to determine the viscosity coefficient γ1(−λ1 in Leslie's notation).
Nematic liquid crystals can be electrically addressed when sandwiched in thin layers. We present in this paper a liquid crystal optical data composer which is X-Y addressed using the electro-optical effect of index modulation, a field effect, realised for an a. c. electric field on an homeotropic structure. It is a 128 x 128 dots display capable of presenting at the same time 1.6 x 104 digital optical data, with overall writing times of a few milliseconds
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