摘要： Photonic circuits are spreading as a viable alternative to conventional electronic circuits. Electro-optic modulators (EOMs) are currently used as switches in telecommunications thanks to their simplicity and speed, however they are driven electrically. Several approaches have been demonstrated to realise all-optical switches such as ring lasers in which the lasing direction is controlled by an input seed, however these devices still require additional electrical or optical pumping. An alternative approach is to exploit the change in resonant frequency of nonlinear resonators with the input power. This has been successfully demonstrated in semiconductor resonators, where the nonlinearity is provided by the carrier generation from two-photon absorption, and in dielectric resonators governed by the Kerr effect. However, this approach needs the input to be in a narrow range of power and detuning from the cavity resonance and is adversely affected by the cavity’s thermal drift due to the high circulating powers. We demonstrate a device that works in a different regime of the Kerr effect. In our case the bistability arises from the twofold contribution of the cross-phase modulation with respect to the self-phase modulation to the refractive index change, Δni ∝ n2(Ii + 2 I j), where i, j are the two possible directions [1,2]. As a consequence, above a threshold power, Pth, light of a given frequency can circulate in just one direction inside the resonator and the switching between the two corresponding states exhibits hysteresis. This regime can be accessed in a much broader range of input powers, from Pth to ～ 5Pth, and the frequency of the laser can drift by up to about 10 GHz thanks to thermal locking [3].