Search for gravitationally lensed interstellar transmissions

Abstract

We explore interstellar light transmission facilitated by gravitational lensing, focusing on axially-symmetric lensing configurations where the transmitter, lens, and receiver are nearly aligned. Positioning an optical transmitter in the lens's focal region, we investigate the caustic formed by a diffraction-limited annular beam of light emitted by the transmitter. We analyze the impact of the lens's point spread function (PSF) on the projected beam's structure, estimate the power delivered to a receiver at interstellar distances, and assess the major noise sources. We determine detection sensitivity in both noise- and signal-dominated regimes. Considering realistic assumptions about the transmitter's performance, we explore signal detection strategies enhanced by the spatial broadening of the received beam, a result of the transmitting lens's PSF. Our findings indicate that detecting lensed optical signals from nearby stars is achievable using established optical engineering technologies. A network of spatially distributed astronomical facilities capable of observations in multiple narrow spectral bands will enhance the search. Our results support the feasibility of interstellar power transmission via gravitational lensing, directly contributing to ongoing optical SETI efforts.