Wavelength independent detection and discrimination of a laser with a sensitivity of 140fW using self-coherence

Wavelength independent detection and discrimination of laser radiation has been performed by detecting the "self coherence" of an incoming light source using interferometry with photon sensitive detectors. The system successfully discriminates between coherent and incoherent sources. Detection of scattered laser light has been performed across the visible spectrum with no filters, internal or external source comparisons. The ultimate detection sensitivity was shown to be 140fW for a continuous wave (CW) HeNe laser at 632nm. We believe this to be the most sensitive wavelength independent detection of a CW laser so far reported