It has long been proven that pyro-optical properties can be used to develop high performance IR detectors without making use of a microelectronic readout circuit. In this application, the sensing materials should have high pyro-optic coefficient, or the refractive index of the materials should have strong dependence on temperature. Polymers showed higher pyro-optic coefficient compared with that of most inorganic materials. Among the polymers, liquid crystals (LCs) attracted more interests for their stronger temperature dependent optical characteristics. In this study, 5CB and 3HHV LCs were selected as examples to investigate their pyro-optic properties for the development of optical readout IR imaging devices. Refractive indices of the 5CB LC for both ordinary and extrodinary light were characterized within the phase transition temperature range. It was found that the no changed slightly with the variation of temperature, while the ne changed dramatically with the change of temperature. For 5CB, when the temperature increased from 22°C to 34 °C, n_e decreased from 1.75 to 1.64 for wavelength of 632.8nm. Results for 3HHV were also reported and analyzed. Another interesting property of the 5CB was that it showed obvious IR absorption in the wavelength range between 3 and 5 μm, which made them more promising for the application as IR sensing materials.

Date Published: 26 August 2010
PDF: 6 pages
Proc. SPIE 7780, Detectors and Imaging Devices: Infrared, Focal Plane, Single Photon, 77800M (26 August 2010); doi: 10.1117/12.858609

Published in SPIE Proceedings Vol. 7780:
Detectors and Imaging Devices: Infrared, Focal Plane, Single Photon
Eustace L. Dereniak; Randolph E. Longshore; Manijeh Razeghi; John P. Hartke; Ashok K. Sood; Paul D. LeVan, Editor(s)