Reversible Optical Isolators and Quasi-Circulators Using a Magneto-Optical Fabry-Pérot Cavity

Nonreciprocal optical devices are essential for laser protection,modern optical communication and quantum information processing by enforcing one-way light propagation.The conventional Faraday magneto-optical nonreciprocal devices rely on a strong magnetic field,which is provided by a permanent magnet.As a result,the isolation direction of such devices is fixed and severely restricts their applications in quantum networks.In this work,we experimentally demonstrate the simultaneous one-way transmission and unidirectional reflection by using a magneto-optical Fabry-Pérot cavity and a magnetic field strength of 50 mT.An optical isolator and a three-port quasi-circulator are realized based on this nonreciprocal cavity system.The isolator achieves an isolation ratio of up to 22 dB and an averaged insertion loss down to 0.97 dB.The quasi-circulator is realized with a fidelity exceeding 99% and an overall survival probability of 89.9%,corresponding to an insertion loss of~0.46 dB.The magnetic field is provided by an electromagnetic coil,thereby allowing for reversing the light circulating path.The reversible quasi-circulator paves the way for building reconfigurable quantum networks.

Steady State Temperature Study on RF LDMOS with Structure Modification

This paper is devoted to temperature analysis on power RF LDMOS with different feature parameters of die thickness, pitch S length and finger width. The significance of these three parameters is determined from temperature comparison obtained by 3D Silvaco-Atlas device simulator. The first three simulations focus on temperature variation with the three factors at different output power density respectively. The results indicate that both the thinner die thickness and the broaden pitch S length have distinct advantages over the shorter finger width. The device, at the same time, exhibits higher temperature at a larger output power density. Simulations are further carried out on structure with combination of different pitch s length and die thickness at a large 1W/mm output power density and the temperature reduction reaches as high as 55%.

Broad-intensity-range optical nonreciprocity based on feedback-induced Kerr nonlinearity

Nonreciprocal light propagation plays an important role in modern optical systems,from photonic networks to integrated photonics. We propose a nonreciprocal system based on a resonance-frequency-tunable cavity and intensity-adaptive feedback control. Because the feedback-induced Kerr nonlinearity in the cavity is dependent on the incident direction of light,the system exhibits nonreciprocal transmission with a transmission contrast of 0.99 and an insertion loss of 1.5 dB. By utilizing intensity-adaptive feedback control,the operating intensity range of the nonreciprocal system is broadened to 20 dB,which relaxes the limitation of the operating intensity range for nonlinear nonreciprocal systems. Our protocol paves the way to realize high-performance nonreciprocal propagation in optical systems and can also be extended to microwave systems.