Aerodyne Research, Inc.

Andrew Freedman

Paul L Kebabian

Charter D Stinespring

This invention provides a system and method that enables the use of incoherent light sources, such as light emitting diodes, to provide for the detection of gaseous species which exhibit broadband absorption features (e.g., nitrogen dioxide and the halogen gases). The light emitting diode (LED) is an ideal light source for such an arrangement in that it can be modulated at high frequencies (allowing for omission of external modulation equipment) and provides sufficient illumination within a reasonably narrow wavelength band as compared to, for instance, an incandescent light source. A further advantage of a LED as a light source compared to alternatives such as a gas discharge or arc lamp is that the light output of the LED is highly stable, limited by the stability of the current source used to drive it. Use of a confocal or near-confocal resonant optical cavity maximizes coupling of the light source to the cavity.

System and method for trace species detection using cavity attenuated phase shift spectroscopy with an incoherent light source

Disclosed herein is a process for producing a thin film of epitaxial material on a substrate surface at low temperatures under ultrahigh vacuum conditions. In general, precursor compounds are deposited, and converted into the epitaxial material, on the substrate surface at a temperature at which they undergo no substantial dissociation. By way of example, a beam-deposited admixture of dimethyl tellurium and dimethyl cadmium is efficiently converted to an epitaxial cadmium telluride crystal on the surface of a GaAs(100) substrate placed in an ultrahigh vacuum chamber by low power, 193 nm laser irradiation (pulse fluence approximately 6 mJ cm.sup.-2) at substrate temperature of -150.degree. C. and by subsequent annealing at 200.degree. C. for 30 seconds. In addition to efficient use of precursors, this process also permits considerable improvement of pattern resolution.

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Chelmsford, MA, United States of America

Andrew Freedman