A novel uncooled long-wave infrared imaging technology with optical readout is proposed and developed targeted for low cost thermal imaging applications. This technology uses the thermo-optic effect in a semiconductor to detect infrared signals rather than the thermal-resistance effect used in traditional microbolometers. The key component of the imager, the focal plane array, is made up of thermally tunable thin film filter membrane pixels. Each thermal pixel acts as a wavelength translator, converting far infrared radiation signals into near infrared signals which are then detectable by off-the-shelf CCD or CMOS cameras. This approach utilizes optical filter and MEMS technologies, to build a low-cost passive long wavelength infrared focal plane array without electrical leads or active cooling. Within one year since the commencement, NETD values of 0.28K in a 160x120 array operating at 22Hz video frame rate have been achieved without temperature control.
Thermo-optic layers of thin film semiconductors are deposited by PEVCD to create thermally tunable bandpass filters for WDM optical networks. Amorphous semiconductor films, adapted from the solar cell and display industries, are the primary ingredient. Single-cavity tunable filters with FWHM=0.085 nm, >40 nm tuning range, and insertion losses 0.2-4 dB are demonstrated. Key enablers for this new family of index-tunable thin film devices are PECVD deposition, large internal temperature changes >400C, high conductivity polysilicon heater films, and extremely robust film adhesion. Possible applications include optical monitoring, add/drop multiplexing, dynamic gain equalization, and dispersion compensation.