# A photonic integrated circuits with reconfigurablenonreciprocal transmission and all-opticalfunctionalities

## TL;DR

This paper introduces a silicon photonic integrated circuit with reconfigurable nonreciprocal transmission and all-optical functionalities, achieved through a mixed cavity system with thermal tuning and nonlinear effects, enabling advanced optical computing applications.

## Contribution

The work demonstrates a novel reconfigurable nonreciprocal photonic circuit with high isolation and all-optical functionalities, surpassing previous silicon photonics nonlinearity-based nonreciprocity methods.

## Key findings

- Large isolation ratio achieved with Fano resonance and EIT peaks.
- Reconfigurable transmission direction via integrated heaters.
- Potential for all-optical switching and computing applications.

## Abstract

We present a photonics integrated circuit on silicon substrate withreconfigurable nonreciprocal transmission that exhibits a large isolationratio and low insertion loss. It also offers ability for all-optical function-alities, like optical computing gates, or a flip-flop. The circuit is a mixedcavity system of which the linear transmission can be tuned as a Fanoresonance or electromagnetically induced transparency (EIT) using twointegrated heaters. With high optical intensity inside the cavity, the Fanoresonance and EIT peak induce a strong distortion due to thermal non-linearities in the cavity, and these distortions depend on the transmissiondirection due to the asymmetric power distribution in the cavities. Theresulting large isolation ratio is attributed to the inherent sharp slope ofthe Fano resonance and the large extinction ratio of the EIT peak. Thus,a high-power forward-propagating signal will trigger the nonreciprocalphenomenon for low-loss transmission, while backward transmission willsee high loss irrespective of its power level, which is an outstanding im-provement upon previously reported nonlinearity induced nonreciprocityin silicon photonics. The reconfigurability of the high transmission direc-tion comes from the efficient control of the mode excitation and couplinginside the cavity using the integrated heaters. Also, by using a separatepump laser, the device could be developed for all-optical functions likeswitching, logic and computing.