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 photon sensitive detectors and a modulating asymmetric interferometer has been modelled. 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 0.1nm over an observation time of 750s.

17 pages, 7 figures