Bah Holdings LLC

Michael Tkachuk

Sergey Suchalkin

Michael Gouzman

There is provided a photodetector, comprising a semiconductor heterostructure having in sequence: a first collection layer having substantially uniform doping of a first doping type; a radiation-absorbing layer having substantially uniform doping of the first doping type and having a band gap less than or equal to that of the first collection layer; and a barrier layer having a band gap greater than that of the radiation-absorbing layer, the top of the valence band of the barrier layer being substantially equal in energy to that of the radiation-absorbing layer where the first doping type is n-type or the bottom of the conduction band of the barrier layer being substantially equal in energy to that of the radiation-absorbing layer where the first doping type is p-type; wherein a first portion of the barrier layer is of the first doping type and a second portion of the barrier layer is of a second doping type, the first portion of the barrier layer being adjacent to the radiation-absorbing layer, forming a heterojunction within the barrier layer which gives rise to a depletion region within each portion of the barrier layer.

Photodetector

Optopair for use in sensors and analyzers of gases such as methane, and a fabrication method therefor is disclosed. It comprises: a) an LED, either cascaded or not, having at least one radiation emitting area, whose spectral maximum is de-tuned from the maximum absorption spectrum line of the gas absorption spectral band; and b) a Photodetector, whose responsivity spectral maximum can be either de-tuned from, or alternatively completely correspond to the maximum absorption spectrum line of the absorption spectral band of the gas. Modeling the LED emission and Photodetector responsivity spectra and minimizing the temperature sensitivity of the optopair based on the technical requirements of the optopair signal registration circuitry, once the spectral characteristics of the LED and Photodetector materials and the temperature dependencies of said spectral characteristics are determined, provides the LED de-tuned emission and Photodetector responsivity target peaks respectively.

Optopairs with temperature compensable electroluminescence for use in optical gas absorption analyzers

A photodetector is provided, comprising: a radiation-absorbing semiconductor region and a collection semiconductor region separated by and each in contact with a barrier semiconductor region; wherein, at least in the absence of an applied bias voltage, the band gap between the valence band energy and the conduction band energy of the barrier semiconductor region is offset from the band gap between the valence band energy and the conduction band energy of the radiation-absorbing semiconductor region so as to form an energy barrier between the radiation-absorbing semiconductor region and the collection semiconductor region which resists the flow of minority carriers from the radiation-absorbing semiconductor region to the collection semiconductor region. Also provided is a method of manufacturing a photodetector.

In one aspect of the disclosure, a gas sensor is provided, comprising: a chamber for containing a gas sample in use, and a radiation source adapted to emit radiation within a first waveband. A photoluminescent material, upon absorption of radiation of a first wavelength within the first waveband, emits radiation of a second wavelength, the photoluminescent material being responsive to the presence of a target gas species in the gas sample. The gas sensor further comprises a luminescence detector assembly. The luminescence detector assembly is adapted to detect radiation of the second wavelength and output a corresponding measurement signal related to the concentration of the target gas species. An optics assembly is adapted to receive radiation emitted by the radiation source and to converge the radiation towards a location at which the luminescence detector assembly cannot receive radiation.

Gas sensor

A gas or particulate sensor is provided for the detection of at least two target gases and/or particulates. The sensor comprises: a chamber for containing a gas sample under test; a first optical measurement channel configured for the detection of a first target gas or particulate within the gas sample, and a second optical measurement channel configured for the detection of a second target gas or particulate within the gas sample, each optical measurement channel comprising a respective optopair which comprises a radiation source adapted to emit radiation and a radiation detector adapted to output a signal in response to detected radiation; and focusing optics able to form an image of an object. At least the first optical measurement channel is configured such that the radiation detector of the respective optopair receives via the focusing optics an image of the corresponding radiation source, whereby the radiation received from the radiation source by the radiation detector is modified by the first target gas or particulate present in the gas sample such that the output signal from the radiation detector provides information as to the presence of the first target gas or particulate in the gas sample.

Optical gas and/or particulate sensors

An optical absorption gas analyzer is provided for determining the concentration of a target gas in a sample, comprising: a chamber for containing the sample in use; an optopair, comprising a light emitting diode (LED) arranged to emit radiation into the chamber and a photovoltaic radiation detector arranged to detect radiation transmitted through the chamber from the LED and to output a corresponding detection signal S; a temperature sensor arranged in thermal contact with the LED and the photovoltaic radiation detector, and to output a temperature signal T representing the temperature of the optopair; a memory having stored therein data representative of the baseline detection signal Soutput by the optopair in the absence of the target gas as a function of the temperature of the optopair across a range of temperatures; and a processor adapted to generate a differential detection signal Sindicative of the concentration of target gas in the sample by retrieving from the memory the baseline detection signal Scorresponding to the temperature signal T and calculating the difference between the detection signal Sand the baseline detection signal S.

Optical absorption gas analyser

An optical absorption gas analyzer for determining the concentration of a target gas in a sample is disclosed. The analyzer comprises a chamber for containing the sample in use; a radiation source assembly arranged to emit radiation into the chamber; a first radiation detector assembly arranged to detect radiation transmitted along a first optical path through the chamber and a second radiation detector assembly arranged to detect radiation transmitted along a second optical path through the chamber, wherein the length of the second optical path which the sample can intercept is shorter than that of the first optical path. The analyzer further comprises a processor adapted to generate a sensing signal Sbased on the detected radiation transmitted along the first optical path and a reference signal Sbased on the detected radiation transmitted along the second optical path. The processor determines the concentration of the target gas in the sample based on a comparison of the sensing signal with the reference signal.

An optical absorption spectrometer is provided for determining the concentration of a substance within a sample. The optical absorption spectrometer comprises a first radiation source for supplying radiation to the sample to be measured; at least one cavity for containing the sample during measurement; and a detector assembly for detecting radiation transmitted along first and second optical paths through the sample, the length of the first optical path being greater than that of the second optical path.

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Sayville, NY, United States of America

Michael Tkachuk