Y.I. Malashko, V.M. Khabibulin
Long-distance laser energy transfer is currently considered a crucial task in energy supply for autonomous air- and spacecrafts. For preliminary detection of the pointlike object, a new method is offered using illumination of the objects by means of a radio locator with the subsequent capture of the reflected signal by the receiving device installed into the transferring laser channel. The method enables the laser channel to be used simultaneously as a radio channel without worsening the characteristics of the laser channel. It is implied that the mirrors in the radio signal transfer system have metal coatings.
The method proposed utilizes diffraction of a radio-frequency radiation on a secondary mirror of the transmitting optical telescope. The region of the diffracted axisymmetric radio emission beam is coaxial with the laser beam. Given that a radio wavelength is 103-104 times longer than a laser wavelength, the diffraction angle of a radio emission would be as many times larger. This property enables axisymmetric coupling of a considerable amount of radio beam power out of the laser beam region at short distances. The diffracted radio beam is either trapped by the concave (annular) antenna or focused on the receiver of a radio signal installed in a shadow zone of a laser beam. The optimal diameter of the antenna coincides with the diameter of the first dark Airy ring.
The estimated coefficient of radio power transfer from the secondary mirror to the focusing antenna shows that the transfer coefficient reaches 0.9 (wavelength l=30 mm) at a distance of 3 meters and 0.7 (l=5 mm) at a distance of 10 m.
The proposed method of object detection by a reflected radio signal can be used for mobile laser stations equipped with illuminator radar or with external radio illuminator.