Systems and methods for wirelessly transmitting power across a room or space are disclosed herein. One such system is comprised of a power receiving element positioned to receive wireless power transfer, comprised of a power receiving cell and a retroreflector positioned proximate the power receiving cell, and a power transmission element configured to wirelessly transmit power towards the power receiving element. The power transmission element includes an optical power transmitter configured to emit a first laser beam with a first power density towards the receiving cell, a guard beam emitter positioned proximate the optical power transmitter and configured to emit a second laser beam with a second power density towards the retroreflectors, a light detector positioned proximate the guard beam emitter and configured to detect light reflected by the retroreflectors, and an interlock system configured to interrupt power transmission when a decrease in light incident from the retroreflectors is detected.