Sensitive detection of IR photons with picosecond time resolution

Parametric upconversion is shown to be a powerful detection scheme for picosecond pulses in the IR. Tuning characteristics, spectral bandwidth, and solid angle of acceptance of the process are discussed. The linear response of the setup is demonstrated over a large range of 8 orders of ten in agreement with theoretical arguments. Using pump pulses of 1 ×10⁻⁵ J, IR signals with 1 ×10⁻¹⁵ are detected with a time resolution of approximately ˜10 psec.