  Interest in free-space optics (FSO) is rapidly growing as a potential
solution for the backhaul of next-generation mobile or low-orbit satellite
communications. Various techniques have been suggested for employing an
intelligent reflecting surface (IRS) in FSO systems, such as anomalous
reflection, power amplification, and beam splitting. It is possible to deliver
more power to the receiver (Rx) by collimating or focusing the reflected beam
at the Rx lens. In this study, we propose a phase-shift design of an IRS for
beam focusing. In addition, we propose a new pointing error model and an outage
performance analysis applicable when the beam width is comparable to or less
than the aperture size of the Rx. The analytical results are validated by Monte
Carlo simulations. This study provides essential preliminary results for future
researches that assume a focused beam in FSO systems.
