Based on the second-order nonlinearity, we present a bidirectional tunable all-optical switch at C-band by introducing backward quasi-phase-matching technique in Mg-doped periodically poled lithium niobate (MgO:PPLN) waveguide with a nano-structure called multiple resonators. Two injecting forward lights and one backward propagating light interact with difference frequency generations. The transmission of forward signal and backward idler light can be modulated simultaneously with the variation
A surface plasmon resonance (SPR) sensing system based on the optical cavity enhanced detection technique is experimentally demonstrated. A fiber-optic laser cavity is built with a SPR sensor inside. By measuring the laser output power when the cavity is biased near the threshold point, the sensitivity, defined as the dependence of the output optical intensity on the sample variations, can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity i