The Israeli start up company Sirica has developed a novel technique for the production of an infrared-to-visible light converter. In order to manufacture the ultimate infrared (IR) “detector on a chip”, the converter will be integrated with silicon based CMOS/CCD image sensors and their electronics.
Modern IR detectors require either cooling to ultra low (cryogenic) temperatures to prevent thermal/dark currents (in quantum detectors), or vacuum packaging to provide thermal isolation (in thermal detectors). These requirements affect their prices, making them too costly for the mass market.
The quantum detectors generate an output signal proportional to the number of absorbed photons energetic enough to increase the device’s conductivity. In order to reduce thermal generation of free carriers, which would compete with the optically generated ones, cryogenic cooling is required.
Silicon-based visible-light detectors used in digital still and video cameras are not suitable for the detection of infrared radiation. Silicon is transparent to electromagnetic waves longer than 1.1 microns, whereas the atmosphere permits passage of infrared waves in two wavelength windows of 3-5 micron and 8-14 micron.
Sirica presents a new approach enabling quantum IR detection even at room
temperature. The operating mechanism is based on the up-conversion of photon energy in the silicon based layer, integrated with a CMOS/CCD image sensor. Free charge carriers in this layer are heated and, when excited by IR photons, generate electron-hole pairs. These pairs are further converted to visible photons detectable by commercial CMOS/CCD sensors. The energy required for up conversion of IR photons to more energetic visible ones is provided by an external pumping light source.
According to Sirica’s statement, this technology will enable low cost night vision systems without compromising performance specs. The company hopes to open the previously unreachable mass market, applying this technology to produce devices such as driver night and haze vision systems.
TFOT recently covered a different commercial IR technology developed by the U.S. company FLIR, called PathFindIR. The PathFindIR is a compact thermal imaging camera for cars, designed to ensure safe driving even on the darkest nights or on the stormiest days.
For more information on Sirica’s new IR technology see the company’s website.