Low-cost thermo-optic imaging sensors: a detection principle based on tunable one-dimensional photonic crystals.

Infrared (IR) sensors employing optical readout represent a promising class of devices for the development of thermographic imagers. We demonstrate an infrared radiation detection principle based on thermally tunable one-dimensional (1D) photonic crystals acting as optical filters, integrated with organic and inorganic light emitting diodes (OLEDs and LEDs, respectively). The optical filters are composed of periodically assembled mesoporous TiO2 and SiO2 layers. Due to the thermal tunability of the transmission spectrum of the optical filter, the intensity of light passing through the filter is modulated by temperature. The tuned spectrum lies in the visible region and, therefore, can be directly detected by a visible-light photodetector. The thermal response of the luminance of the OLED-photonic crystal ensemble is 3.8 cd m(-2) K(-1). Furthermore, we demonstrate that the local temperature profile can be time and spatially resolved with a resolution of 530 by 530 pixel, thus enabling a potential application as an infrared imaging sensor featuring low power consumption and low fabrication costs.