Liquid Optical Switch Based on Total Internal Reflection

Abstract

In this letter, we demonstrate a liquid optical switch based on total internal reflection. A conductive liquid (Liquid-1) is filled in the chamber and surrounded by a nonconducting liquid (Liquid-2). The refractive index of the transparent cube (n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ), Liquid-1 (n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ), and Liquid-2 (n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) meet the relations of nc > n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , and n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> > n1. In initial state, the cube is totally immerged in Liquid-1. The incident light is adjusted to just meet the condition of total internal reflection when it illuminates the solid-liquid interface. The light is totally reflected by the cube, and the device shows light-OFF state. When we apply a voltage to sidewall electrodes, Liquid-1 stretches toward to the sidewalls. The cube' top surface comes out from Liquid-1. The interface of solid/liquid changes. The light is refracted by Liquid-2. The device shows light-ON state. So the device can achieve the functions of optical switch. Because the light can be totally reflected by the cube, the device can attain 100% intensity attenuation. Our experiments show that the device has a fast switch time of 49 and 53 ms from light-OFF (ON) to light-ON (OFF), respectively. The proposed optical switch has potential applications in variable optical attenuators, information displays, and light shutters.