Abstract

Electromagnetic radiation is known to carry both linear and angular momentum. The latter can be divided in a spin part, associated with the field polarization, and an orbital part, associated with the field distribution. Experimental study has been restricted almost exclusively to the effect of linear momentum. As an exception, Beth studied in 1936 the effect of spin angular momentum of radiation.^[1] He passed circularly polarized light from a tungsten lamp through a half-wave plate, thereby changing the handedness of the light, and was able to measure the mechanical torque on the plate due to the transfer of angular momentum. The orbital angular momentum of radiation has been discussed almost exclusively in connection with multipole radiation.^[2] Here we show that a TEM laser mode can have large orbital angular momentum and we propose a study of its mechanical consequences.

© 1992 IQEC