The noise-suppression techniques of label-free optical ring resonator sensors are crucial to improve their practical sensing capabilities for biochemical analysis and detection in extremely small detection concentration. We have developed a self-referencing optofluidic ring resonator (SR-OFRR) to vastly improve its sensing capability as a label-free optical biosensor. By monitoring the mode-splitting separation generated on a coupled ring resonator system, the common-mode noise is suppressed by 2 orders of magnitude without any external noise-suppression techniques. In this work, we first carried out theoretical analysis to elucidate the sensing principle and then applied the SR-OFRR biosensor to experimentally detect bovine serum albumin with a concentration detection limit on the order of 1 pg/mL (∼15 fM).

The second-order nonlinearities in thermally poled lead borate glasses were studied. After poling with different electrodes, both bulk and near surface second-order nonlinearities were obtained. The second harmonic generation signal from near surface effect was two orders of magnitude larger than the bulk effect. By simulating the poling process with a multiple carrier model, we concluded that the bulk second-order nonlinearity was caused by the deficiency of Pb2+ in a thick layer after poling, and the near surface second-order nonlinearity was caused by the depletion of H+ in a thin layer when H+ injection from the atmosphere was blocked.

Ultrafast third-order nonlinear optical responses of GeSe2–In2Se3–CsI chalcohalide glasses have been measured by using optical Kerr effect (OKE) technique at 1064 nm. The obtained third-order nonlinear susceptibility χ(3) and nonlinear refractive index n2 are as large as 9.46 × 10−12 esu and 6.5 × 10−14 cm2/W, respectively. The relationship between glass compositions and the third-order nonlinear optical responses was analyzed by Raman spectra in terms of structural evolution. It is suggested that the tetrahedral units play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses. The present glass is a promising material for all-optical switching devices.

A novel thermo-optic multimode interference (MMI) switch with a tapered heating electrode was proposed and the performance of the switch was simulated. An analytical steady-state heat-conduction model is also presented. In the design, one tapered heating electrode is used to alter the refractive index in the multimode slab region to realize the switching function. The simulation results indicate that the MMI switch can provide high extinction ratio, and good polarization- and wavelength-independence. The electric power consumption for the MMI switch is half of that of a switch with a straight heating electrode and similar to that of a Mach–Zehnder interferometer switch.