Optical properties of an “anomalous” droplet

Abstract

The idea of using liquids to construct optical elements with controllable characteristics goes back to Newton, who suggested using the surface of mercury in a rotating container as a parabolic mirror. Such progress has now been made in this field that liquid metal telescopes with a mirror diameter of 4 m are now operating successfully. 1 In 1958, Block and Harwit 2 suggested using the thermocapillary-deformed free surface of a liquid as an optical element. The phenomenon of self-focusing of laser radiation observed when an incident beam is reflected from a thermocapillary deformed liquid layer was studied in Refs. 3‐6. Following the discovery of concentration-capillary convection induced by the thermal action of light in thin films of solutions of positively strain-active substances 1! in highly volatile solvents, it was suggested that the ‘‘anomalous’’ droplet 5 formed as a result of this effect could be used as a varifocal liquid lens. Bezuglyi 7 showed that a steady-state anomalous droplet could be achieved, and this was confirmed experimentally 8 using a mixture of acetone and a saturated solution of rhodamine G in water.