Electroluminescence excited by infrared radiation has been observed in GaP light‐emitting diodes (LED’s) at low temperatures providing a new efficient method to convert infrared radiation within a broad spectral range into visible light. Using 10.6‐&mgr;m radiation of a CO2laser an up‐conversion quantum efficiency of 3.4×10−6was found. If a low dark current photomultiplier is employed to detect the LED emission the dominant noise source is due to conversion of thermal background radiation yielding a noise equivalent power of NEP=1.6×10−9W/Hz1/2.