Gravitational lensing for interstellar power transmission

We investigate light propagation in the gravitational field of multiple gravitational lenses. Assuming these lenses are sufficiently spaced to prevent interaction, we consider a linear alignment for the transmitter, lenses, and receiver. Remarkably, in this axially symmetric configuration, we can solve the relevant diffraction integrals---result that offers valuable analytical insights. We show that the point-spread function (PSF) is affected by the number of lenses in the system. Even a single lens is useful for transmission either it is used as a part of the transmitter or it acts on the receiver's side. We show that power transmission via a pair of lenses benefits from light amplification on both ends of the link. The second lens plays an important role by focusing the signal to a much tighter spot; but in practical lensing scenarios, that lens changes the structure of the PSF on scales much smaller than the telescope, so that additional gain due to the presence of the second lens is independent of its properties and is govern solely by the transmission geometry. While evaluating the signal-to-noise ratio (SNR) in various transmitting scenarios, we see that a single-lens transmission performs on par with a pair of lenses. The fact that the second lens amplifies the brightness of the first one, creates a challenging background for signal reception. Nevertheless, in all the cases considered here, we have found practically-relevant SNR values. As a result, we were able to demonstrate the feasibility of establishing interstellar power transmission links relying on gravitational lensing---a finding with profound implications for applications targeting interstellar power transmission.