Background-limited operation of 4K-cryocooled THz photoconductive detector system with a wide frequency range of 0.8 to 4THz

We have demonstrated a terahertz (THz) detector system which employs three terahertz photoconductive semiconductor detectors to realize a response to a wide frequency range of 0.8 to 4 THz and a mechanical 4 K GM refrigerator instead of a liquid helium container to perform practical and convenient use. Optical and electrical performance of the THz detector system was evaluated at an operation temperature of 4 K under 300 K background radiation environment, which have proved the detector system can achieve background limited NEP (noise equivalent power) for THz detection even if vibration noise of mechanical cooler is present.