The design of the present laser optical torquemeter arose from the need to measure the mechanical power furnished by a prototype of chirale turbine, which exploits the lift force produced in the rotor, due to the "Magnus effect." The particular optical reading system allows the device to determine both the torque and the mechanical power. The torque value is obtained through the reading of the torsional angle. From this value, together with that of the transmission shaft angular speed measured by the same torquemeter, the mechanical power of the turbine is calculated. The optical system output signals are acquired, processed and elaborated by a virtual logic circuit, simulated by means of a suitable home-made software in LabVIEW environment. The torquemeter has been tested operating with the prototype of turbine in a wind tunnel.