Del Bino Leonardo, Moroney Niall, Del'Haye Pascal
Opt Express. 2021 Jan 18;29(2):2193-2203. doi: 10.1364/OE.417951.
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.
克尔非线性效应可能是许多数字光子电路的关键促成因素，因为它能实现全光存储器和开关所需的双稳态。一种常用技术是利用克尔频移来控制谐振器的谐振频率，并将其用作双稳态、光可调滤波器。然而，这种方法仅在较窄的功率和频率范围内有效，或者需要使用辅助激光器。另一种方法是利用自相位调制和交叉相位调制相互作用产生的反向传播光态之间的不对称双稳性，这使得光只能沿一个方向进入环形谐振器。逻辑高态和低态可以用光的循环方向来表示和存储，并通过调制输入功率进行控制。在此，我们研究了这种器件的开关速度、工作激光频率和功率范围以及对比度。在原理验证器件中，我们在1 GHz的光频率范围内以及覆盖超过一个数量级的工作功率范围内实现了2 Mbps的比特率。我们还计算得出，集成光子电路的比特率可达Gbps量级，为实现能够在单一激光频率下运行且无需额外电功率的稳健、简单全光存储器、开关、路由器和逻辑门铺平了道路。
