Pressure of Electromagnetic Radiation on a Linear Vibrator

Abstract

Nowadays the pressure of electromagnetic radiation in the optical range is widely used in laser traps (so called optical tweezers or single-beam gradient force trap) to control the position of microparticles, biological cells and other microscopic objects. This is possible by focusing the laser radiation into the area of several micrometers in size. The intensity of the radiation in the area is sufficient to hold particles in the beam and manipulate them. We are interested to research similar possibility in the microwave range of wavelengths. However we had faced a number of difficulties in this range: the size of the focal region is much larger, the radiation intensity is less, and to control microscopic objects by means of radiation pressure very high powers are required. And we decided to consider the known effect of a very strong interaction of thin conducting fibers (metal, semiconductor, graphite) with microwave radiation. The efficiency factor of radiation pressure on such objects reaches values of several hundreds and thousands. This can be used to control objects in the form of electrically thin metal conductors by means of radiation pressure. Methods for calculating the pressure of electromagnetic radiation on an infinitely long circular cylinder are known. In this paper we propose a method for calculating the radiation pressure on a circular cylinder (vibrator), the length of which is comparable to the radiation wavelength. We have found out that when the vibrator length is close to half the wavelength, the radiation pressure efficiency factor is much larger than for an infinite cylinder. We have obtained the dependence of the radiation pressure efficiency factor on the length and diameter of an absolutely reflecting and impedance vibrator. It decreases with decreasing conductivity. An infinite cylinder at a certain value of conductivity has a maximum of the radiation pressure efficiency factor.