Inverse Design of Nonvolatile Reconfigurable Mode Generator and Optical Circulator Based on a Novel Concept of a Fully-Digitized Module

Based on the novel concept of a fully-digitized module, we employ a forward-designed-assisted inverse design method to design a nonvolatile reconfigurable mode generator and an optical circulator, assisted with a phase change material. The mode generator can selectively output different modes. The fundamental transverse electric (TE
₀
) or TE
₁
modes can be selectively generated when the TE
₀
mode is launched in the input port. The mode generator with an effective footprint of 2.4 μm × 16 μm exhibits the simulated insertion losses of less than 1.0 dB and the simulated crosstalks of lower than –19.0 dB for both the TE
₀
and TE
₁
modes from 1540 nm to 1560 nm. The optical circulator enables the light unidirectional propagation. Photons can be precisely routed from each input port to one adjacent output port in clockwise or counterclockwise directions. The simulated results indicate that the circulator with an effective footprint of 24 μm × 24 μm, can provide both the simulated insertion losses of less than 0.8 dB and the simulated crosstalks of lower than –16.3 dB from 1540 nm to 1560 nm in both clockwise and counterclockwise directions. The fabrication tolerances caused by the expansion or contraction of the etched pattern contour are also investigated. In principle, the proposed frameworks can be extended to an arbitrary number of ports for designing mode generators and optical circulators.