The fast quasiadiabatic approach to optical waveguide design

Abstract

Optical waveguide devices based on adiabatic mode evolution have large bandwidth and fabrication tolerances, but they have longer device lengths in general. We define a suitable adiabaticity parameter for optical waveguides and derive the formulae for engineering the adiabaticity along the waveguide. The fast quasiadiabatic dynamics (FAQUAD) protocol can then be applied to redistribute adiabaticity over the length of the device, speeding up mode evolution in adiabatic waveguide devices. By homogeneously distributing the adiabaticity along the length of the devices, shortcuts to adiabaticity are found for adiabatic waveguide devices, resulting in significant length reductions from the conventional designs. Devices on silicon, including mode (de)multiplexers, polarization splitter-rotators and 3 dB couplers using the FAQUAD approach are discussed. The FAQUAD approach leads to devices that are compact, broadband, and have good fabrication tolerances.