| 摘要 |
733,566. Light-valves. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Oct. 19, 1953 [Nov. 6, 1952], No. 28011/52. Class 40 (3). A valve or modulator for controlling radiations in the infra-red wavelength region comprises a body of transistor material forming a path for the radiation to be controlled and means for varying the density of charge carriers within said body to control the absorption of radiation in the path. In Fig. 1 a crystal 1 of germanium carries a base electrode 2, and further electrodes 3, mounted in parallel, are arranged so that their contact points are spaced not less than twice the length of the carrier diffusion path within the material. The crystal may be mounted with the electrode 2 on a block of insulating material encircled by a coil of wire with its turns spaced as indicated for the contact points and engaging the face of the crystal opposite that carrying the base electrode, Fig. 2 (not shown). In the operating circuit, Fig. 3, a fixed bias is provided by a battery 7 and the modulating voltage at terminal 12 is fed to the grid of a valve 11, the output being applied via the secondary winding 8 of a transformer 9 to vary the emergent light beam 6 by the operation of the modulator on light from a fixed source 5. The crystal 1 may be tapered at its sides 14 from a comparatively large rectangular end surface facing the incident light to an elongated area, and is mounted on an insulating block 4 with a coil 3 attached to respective terminals 13, Figs. 4a, 4b. In a modification, Fig. 4c (not shown), one of the surfaces 14 is plane and perpendicular to the larger end surface of the crystal. The operating conditions of the device are explained mathematically in the Specification. Germanium and silicon are referred to as suitable transistor materials and reference is also made to semi-conductors, such as the sulphide, telluride and selenide of lead. A quarterwave matching layer, preferably of selenium, may be applied to the incident or emergent surface of the crystal. |
