An optical power transfer device includes a transmitter circuit, including a laser light source that is configured to emit coherent light responsive to operation above a lasing threshold, and is configured to emit incoherent light responsive operation below the lasing threshold. A proximity sensor circuit is coupled to the transmitter circuit and is configured to output a detection signal therefrom responsive to authentication of an optical receiver including at least one photovoltaic cell having surface area of about 4 square millimeters or less within a proximity thereof. The transmitter circuit is configured to operate the laser light source below the lasing threshold to emit the incoherent light responsive to an absence of the detection signal from the proximity sensor circuit. Related devices and methods of operation are also discussed.