Ultra-sensitive, room-temperature THz detector using nonlinear parametric upconversion

摘要

We demonstrate sensitive, room-temperature optical detection of terahertz by using nonlinear parametric upconversion. Terahertz radiation at 700 GHz is mixed with pump light at 1550 nm in GaAs crystals to generate an idler wave that is separated, coupled into optical fiber and detected using a triggered Geiger-mode avalanche photo-diode. We demonstrated a power sensitivity of 4.5 pW/Hz~(1/2) using bulk GaAs. Recently, we fabricated quasi phase-matched (QPM) GaAs crystals, using a diffusion bonding process that has significantly enhanced the THz-to-optical conversion efficiency over bulk GaAs. In addition, we have designed 1550 nm AR coatings that have minimal losses at THz frequencies and have further improved the terahertz-to-optical conversion efficiency. The resulting room-temperature THz detector has a noise equivalent power of 800 fW/Hz~(1/2) and a timing resolution of 1 ns.