The purpose of this paper is to demonstrate a light-driven actuator with high energy conversion efficiency. Ordinarily,
light-driven actuators have low conversion efficiency of about 10<sup>-5</sup>%. This is partly due to an inefficient coupling of the
material itself and the actuating mechanism. Our idea is to use a primarily tensioned thin wire as the material since wire can
shrink and stretch in a specific direction. Therefore, we created a light-driven actuator with a wire of shape memory alloy.
Using Argon-ion laser to irradiate the shape memory alloy, we checked the energy conversion efficiency of this actuator.
As a result, we obtained an energy conversion efficiency of about 3.9% that is far greater than the ordinary value for
light-driven actuators. If the reflectivity of the shape memory alloy is considered, the conversion efficiency is doubled to
7.8%. When viewed as a heat engine, 7.8% efficiency corresponds to approximately 27% of the theoretical limit from