A system for high sensitivity, high time resolution detection of an arbitrary spontaneous emission is disclosed. The system may use a local oscillator (LO) for generating an LO input optical signal, and an linear optical mixer for receiving and mixing the input optical signal and an arbitrary spontaneous emission. The 2D detector generates a first component output and a second component. A subsystem receives the component outputs and produces first and second dispersed spectrum output signals. At least a first ultra-high speed camera is used for imaging one of the first or second dispersed spectrum output signals.