Author:  Jingsong Xia     2014-05-04

Optical nonreciprocal transmission is fundamental to realize optical diodes, isolators and circulators, and is in great demand in all-optical signal processing systems. For a device to be an isolator it must block or divert all possible states for backward propagation. However, it is still a large challenge to break Lorentz reciprocity and realize on-chip devices due to material integration and structure design. Numerous efforts have been made to solve this problem, including devices based on magneto-optic effect, nonlinear materials, and time-dependent refractive index and so on. These approaches either are not compatible with complementary metal-oxide semiconductor (CMOS) processes, or are complex in devices design and fabrication process.

Zhang Yong and Xia jinsong et al. demonstrate an all-silicon passive optical diode based on optical nonlinearity in cascaded PhC L3 cavities. An NTR of 30.8 dB and insertion loss of 8.3 dB are realized. An NTR larger than 17 dB is achieved between 1540.72 nm and 1540.80 nm, and an NTR larger than 16 dB is obtained when input power varies between -6.25 dBm and -2.95 dBm.Nonlinear couple mode model for cascaded PhC cavities is established to analyze the behavior of the device. Simulation results show good agreement with our experiment results. The demonstrated optical diode has potential for on chip all-optical signal processing, and has advantages of simple design, easy fabrication process, compact footprint, high NTR and low operation power.

This work was published in OSA Optics Letters (Vol. 39, Issue 6, 1370-1373, 2014) and was partly supported by the Major State Basic Research Development Program of China (grant 2013CB632104, 2013CB933303 and 2012CB922103), National Natural Science Foundation of China (grant 61177049 and 61335002).