An infrared communication system includes a plurality of infrared transceivers for receiving and transmitting infrared signals through the free air in which each transceiver includes: an omnidirectional infrared receiver for receiving infrared signals; an omnidirectional infrared transmitter for transmitting infrared signals; and a controller which determines the direction of arrival and the quality of the signals received by the infrared receiver, and controls the respective infrared transmitter in accordance therewith.

Infra-red communication system

Chalcogenide glasses transmitting in the infrared between 1 and 20 μ — a state of the art review

Distinct glass-forming composition regions were found in the system Ge-S (1) from GeS2 to GeS9 and (2) from GeS1.21 a to GeS1.5 The properties of these glasses, e.g. ir absorption spectra, thermal expansion, extraction of S8 molecules with CS2, Vickers hardness, density, and optical absorption, led to the conclusion that the structures of glasses in the two regions differ. In region (1), the structure is based on a three-dimensional inorganic polymer of polymeric S chains cross-linked with Ge; in region (2), it involves GeS2 (GeS4 tetrahedra) and GeS (GeS6 octahedra) components that can be regarded as network formers and modifiers, respectively.

Properties and Structure of Glasses in the System Ge‐S

The nature of chemical bonds of some chalcogenide glasses is discussed in terms of the chemical bond approach. It was found that there is a correlation between the chalcogenide glass forming ability and the number of lone-pair electrons for a chalcogenide or chalcogenide system. The stable vitreous state can be obtained only if enough lone-pair electrons exist in the structure of the chalcogenide system. The cation in the chalcogenide glasses may interact with the lone-pair electrons of a bridging chalcogen atom and influence the glass forming ability. A simple criterion for computing the ability of a chalcogenide system to retain its vitreous state is proposed. Experimental results support the above analysis.

Chemical bond approach to the chalcogenide glass forming tendency

New compouning techniques were devised to prepare high-purity Ge28Sb12Se60 (TI 1173)and Ge33As12Se55 TI 20). The methods were based on the combination of the reactant purification and compounding steps. The goal of the program was to establish the absorption limit for the glasses and to lower the absorption at 10.6 μm. At the present purity level, the GeSbSe glass is found to have an absorption level of about 0.01 cm−1 at 10.6 μm while the absorption level for the GeAsSe glass is 0.05 cm−1. Underlying causes for the limits are discussed along with the possibilities for improvement.

Infrared absorption of some high-purity chalcogenide glasses☆

New high temperature infrared transmitting glasses

Several (Hg, Cd) Te semiconductor alloys have properties which make them useful as solid state detectors. However, homogeneous alloy single crystal preparation requires unusual treatment. A two-step process is necessary because of the liquidus-solidus composition disparity at the melting point. Laue topography was found to be an efficient tool for optimizing parameters in an initial quench (to preserve homogeneity) and a subsequent solid state recrystallization (to promote large grain growth). Crystal perfection analysis using polychromatic X-ray diffraction is not an entirely new concept, but our initial interest led to a simplified Laue topography technique which is useful for rapid characterization of various macroscopic crystal defects. The utility of this method is demonstrated by a study of defects in bulk (Hg, Cd)Te crystals.

Rapid, Nondestructive Evaluation of Macroscopic Defects in Crystalline Materials: The Laue Topography of (Hg,Cd)Te

Ge-se-te glass and infrared detection system

Ge-te-as glasses and method of preparation

A method for producing homogeneous ingots of an alloy in which one of the components thereof has a high vapor pressure includes the step of sealing the desired alloy components in a quartz ampoule sufficiently large to include a vapor space therein and heating the ampoule and its contents to at least a temperature at which the components will form a homogeneous liquid mixture. An example of an alloy which can be produced by the instant process is an alloy of cadmium, mercury and tellurium. The method of this invention also includes the steps of quenching the homogeneous alloy from the liquid to the solid state while maintaining a relatively high vapor pressure in the vapor space in the ampoule above the space occupied by the alloy. The high vapor pressure can be maintained in the vapor space by thermally insulating the vapor space during the quenching step. The preferable form of quenching is by immersing only a portion of the space occupied by the alloy in a quenching bath, for example, a quenching oil.

Maurice J Brau

Papers

New high temperature infrared transmitting glasses

Rapid, Nondestructive Evaluation of Macroscopic Defects in Crystalline Materials: The Laue Topography of (Hg,Cd)Te

Ge-se-te glass and infrared detection system

Ge-te-as glasses and method of preparation

Method of producing homogeneous ingots of a metallic alloy