The grating structure introduced by the fabrication of the symmetric Mach-Zehnder interference(MZI) structure is an important reason of the high crosstalk to optical switches.A new design of a 1×2 low crosstalk polymer optical switch with asymmetric MZI structure is presented.The coupling between guided modes and radiation modes can be restrained effectively by this structure.The result indicates that the crosstalk of this device can be improved from -20 dB to -50 dB.At the same time,the voltage...