Optical memories and switching dynamics of counterpropagating light states in microresonators

Abstract

The Kerr nonlinearity can be a key enabler for many digital photonic circuits as it allows access to bistable states needed for all-optical memories and switches. A common technique is to use the Kerr shift to control the resonance frequency of a resonator and use it as a bistable, optically-tunable filter. However, this approach works only in a narrow power and frequency range or requires the use of an auxiliary laser. An alternative approach is to use the asymmetric bistability between counterpropagating light states resulting from the interplay between self-and cross-phase modulation, which allows light to enter a ring resonator in just one direction. Logical high and low states can be represented and stored as the direction of circulation of light, and controlled by modulating the input power. Here we study the switching speed, operating laser frequency and power range, and contrast ratio of such a device. We reach a bitrate of 2 Mbps in our proof-of-principle device over an optical frequency range of 1 GHz and an operating power range covering more than one order of magnitude. We also calculate that integrated photonic circuits could exhibit bitrates of the order of Gbps, paving the way for the realization of robust and simple all-optical memories, switches, routers and logic gates that can operate at a single laser frequency with no additional electrical power.

Real-time imaging of standing-wave patterns in microresonators

“…In a lot of applications, backscattering and the resulting generation of standing waves generated inside a microresonator is a topic of great interest ( 22 – 27 ). It can not only promote our understanding of fundamental physics, such as strong coupling between the atom and microcavity ( 28 ), symmetry breaking phenomena, ( 29 – 33 ) and cavity quantum electrodynamics (cavity QED) ( 34 , 35 ), but also be a fascinating tool to realize various applications ( 36 , 37 ). For instance, standing waves can be used for precision sensing, in which slight variations of the forward and backward propagating laser fields can significantly alter the distribution of the interference pattern inside the cavity ( 12 , 14 , 15 ).…”

Multi-stage spontaneous symmetry breaking of light in Kerr ring resonators

“…In the first example, two, otherwise identical, input beams enter the resonator in opposite directions. The evolutions of these field, including their SSB, have been studied extensively theoretically [6][7][8][9][10][11][12][13] , and, more recently, experimentally [14][15][16][17][18] . The second example involves a single, linearly polarised, laser input splitting into two orthogonally polarised components.…”

Spontaneous symmetry breaking of non-Hermitian coupled nano-cavities

“…Besides timereversal symmetry breaking, another consequence of symmetry disruption is spontaneous symmetry breaking of two optical modes. This phenomenon primarily originates from an imbalance modulation between two competing optical modes, for instance, polarisations 11,12,13,14,15,16 , and clockwise (CW) and counterclockwise (CCW) propagation within ring resonators 17,18,19,20 . Nonlinearity in optics establishes a distinctive framework for the examination of symmetry breaking 16 .…”