Infrared system can detect 300 kilometers

With the increase in the number of stealth fighters and the expansion of the scope of equipment, infrared searching and tracking system (IRST) has gradually become the urgently needed equipment for fighters. Although the stealth fighter has only a small radar cross section (RCS), IRST mainly tracks the target through the exhaust flame of the engine and the high temperature generated by the friction between the fighter and the air.

Although stealth fighters have corresponding precautions, including spraying specular metal coatings, they can not completely shield the heat generated by stealth fighters. Because the infrared signal comes not only from the heat generated by the engine, but also from the heat generated by the friction between the nose, wings and air during the high-speed flight of the aircraft.  

Common aperture optical system of single photon laser and medium wave infrared, it can detect infrared signals emitted by airliners within 300 kilometers.

Usually, it is very difficult for us to increase the distance of IRST, because only a few photons can be captured by the observation lens of the infrared system. The solution is to use single photon detectors (SPD), which can accurately detect and observe single photons.