Athermal Study Of Liquid Crystal Devices In Optical Switch

Liquid crystal device is an important component of optical switch in light direction selection.In a light switch,the liquid crystal is generally sealed in thin glass panels coated with an anti-reflection film.Liquid crystal material itself has a large coefficient of expansion;the volume will expand at high temperature,and contract at low temperature.The expansion coefficient of glass is much smaller than that of liquid crystal.Liquid crystal material has the characteristics of incompressibility,so at high temperature it forms convex lens and concave lens at low temperature.The lens effect caused by temperature changes the direction of the beam transmission through the liquid crystal.In actual production,9%of the product fails due to excessive coupling loss at high and low temperatures.It is of great significance to improve the performance of the product by studying the athermalization in optical switch based on liquid crystal technology.This paper studies the temperature characteristics of liquid crystal in optical switch devices,calculates and analyzes the effect of lens effect on optical switch caused by temperature,and puts forward the corresponding temperature compensation measures to reduce the temperature fluctuation.The main studies on the lensing effect of liquid crystals at high and low temperatures are as follows:1)The temperature model of liquid crystal box structure was analyzed,the relationship between the width and thickness of liquid crystal box and the lensing effect was obtained.Through the actual calculation of the parameters,the maximum offset of the optical path brought by the lens effect can be reduced from 135 um to 34um.At the same time,the sample of liquid crystal box was made according to the optimized parameters,and the experiment was carried out to verify the correctness of the theoretical analysis.2)A scheme of correction of light path deviation caused by temperature by adding a compensation lens is proposed.A convex lens with positive focal degree is formed in the liquid crystal box at high temperature;a concave lens with negative focal degree is inserted before the beam is incident to the liquid crystal box to compensate the convex effect.The compensation effect is calculated theoretically in this paper.Divide the temperature into several small ranges and design 5 sorts of lens that can be inserted to reduce the offset,the offset is reduced from the original 135 um to 23um.Through the study of the temperature characteristics of liquid crystal devices in the photolithography,it is shown that the optimal structure parameters of liquid crystal box and the scheme of compensation mirror can effectively improve the lens effect of liquid crystal box,so as to strengthen the temperature stability of the whole optical system,and realize the demand of athermal switch.In the practical application,we can choose the most suitable improvement method according to the actual situation.The qualified rate of the product has been improved effectively,and the failure efficiency has been reduced from 9%to 1%.