On-chip ultra-small arbitrary-elliptical-polarization converters

On-chip arbitrary-elliptical-polarization converter plays a key role in optical information processing. However, the traditional method of manually adjusting parameters for designing devices is limited in function. In this letter, on-chip ultra-small arbitrary-elliptical-polarization converters are realized through optimization algorithms based on genetic algorithm (GA) combined with finite element method (FEM). The converters can realize the function of arbitrary ellipticity angle conversion of full polarization states. The size of the core device is only 1 μm × 1 μm, which is very conducive to high-density integration. The difference between the ideal output ellipticity angle and the actual output ellipticity angle of each device is no more than 2 degrees. In addition, it is proved that the use of optimization algorithms can easily design arbitrary-elliptical-polarization converters with different materials, different structures and different wavelengths, and the design of three-dimensional arbitrary-elliptical-polarization converters is also verified by using the optimization algorithm. This work provides an efficient design method for arbitrary polarization state conversion, showing its significance in improving the information capacity in optical communication.