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Absolute linearity measurements on a PbS detector in the infrared
1Optical Radiation Team, Division of Quality of Life, National Physical Laboratory, Teddington, UK. e.theo@npl.co.uk
Applied Optics
|April 21, 2006
Summary
This study reveals significant nonlinearity in commercial lead sulfide (PbS) detectors, even at low infrared power levels. Researchers caution users about these poor linearity characteristics impacting measurements.
Area of Science:
- Optoelectronics
- Infrared Detectors
- Materials Science
Background:
- Photoconductive detectors are crucial for infrared applications.
- Lead sulfide (PbS) detectors are widely used due to their sensitivity.
- Understanding detector linearity is essential for accurate measurements.
Purpose of the Study:
- To experimentally investigate the nonlinearity characteristics of a commercial thin-film PbS detector.
- To quantify the deviation from linearity under various infrared illumination conditions.
- To identify factors influencing the nonlinearity of PbS detectors.
Main Methods:
- Utilized the National Physical Laboratory detector linearity characterization facility.
- Employed infrared radiation at specific wavelengths (e.g., 2.2 microm).
- Varied incident radiant power, spot size, and irradiance on the detector's active area.
Main Results:
- Demonstrated significant deviation from linearity even at low radiant power (e.g., 0.6 microW).
- Reported a linearity factor of approximately 0.8 under specific test conditions.
- Observed nonlinearity to be dependent on illuminated spot size and radiation wavelength.
- Found nonlinearity to be a function of irradiance below 1 microW mm(-2).
Conclusions:
- Commercial thin-film PbS detectors exhibit poor linearity characteristics.
- Users of PbS detection systems must be aware of these limitations.
- Nonlinearity is influenced by illumination parameters, necessitating careful experimental design.
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