A Proposed Method for a Photon-counting Laser Coherence Detection System to Complement Optical SETI

Abstract

The detection of laser radiation originating from space is a positive indicator of Extra Terrestrial Intelligence (ETI).Thus far, the optical search for ETI (OSETI) has looked for enhanced brightness in the form of either narrow-band spectral emission or time correlated photons from laser pulses. In this paper, it is proposed to look for coherence properties of incoming light in a manner that can distinguish against atomic emission lines. The use of photonsensitive detectors and a modulating asymmetric interferometer has been modeled. The results suggest that the sensitivity of detection for continuous laser sources would be better than current spectroscopic approaches, with detection thresholds of <1 photon s−1 m−2 against a background with a spectral bandwidth of 0.1 nm over an observation time of 750 s.