Abstract
A silicon waveguide consisting of passive parity-time (PT) symmetry optical potentials connected with a distributed Bragg reflector (DBR)-based resonator is proposed to achieve nonreciprocal waveguide transmission. The unidirectional reflectionless waveguide implementing PT symmetry is discussed by consistent coupling mode theory and finite-difference time-domain (FDTD) simulation results. Due to the high field confinement in the DBR cavity, transmission of a light pulse through the device is analyzed in the nonlinear optical regime using FDTD simulations. The combination of the nonlinear DBR cavity and the passive PT symmetric grating results in unidirectional transmission in the silicon waveguide, while still keeping the reflection minimum in the desired direction. The numerical simulation shows an extinction ratio of about 20 dB at the telecom wavelength of around 1550 nm.
Highlights
Nowadays, Si photonics has become a crucial technology in optical communications and computing due to the recently demonstrated on-chip integration of various compact optical devices [1]–[3]
We have proposed a device cascading a passive PT grating and a distributed Bragg reflector (DBR) cavity to realize the unidirectional transmission in a Si waveguide
The results show that, with an incident pulse with its peak amplitude of 1 Â 109 V/m, unidirectional transmission with an extinction ratio of 20 dB at 1549.145 nm in the forward direction
Summary
Si photonics has become a crucial technology in optical communications and computing due to the recently demonstrated on-chip integration of various compact optical devices [1]–[3]. It is of great importance to overcome challenges in designing on-chip integrated devices that can control light flows in different spatial directions as desired It requires the breaking of time reversal symmetry and Lorentz-reciprocity of an optical system to achieve one-way nonreciprocal light transmission, which is typically associated with the Faraday effect [4], [5] where external magnetic fields are applied to break the space–time symmetry. This approach requires materials with appreciable Verdet constants, and it may not be compatible with complicated on-chip integration schemes and fabrication.
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