Optofluidics has integrated advantages of both micro/nano-photonic devices and microfluidics, and it provides a novel and flexible platform for the manipulation and interaction of fluid and light. Especially, optofluidic ring resonator (OFRR) has attracted intense attention due to their important applications, as a functional optofluidic component. OFRR has taken advantages of the high sensitivity of an optical resonator and the unique properties of liquids to perform as a promising platform for sensing, laser, biochemical analysis and detection, and research on nonlinearity and optomechanics. As to a photonic device, the spectral tunability is imperative. As reported in previous work, tunable OFRRs were achieved by modification of liquid, electrowetting and electric microheater. However, there is still no work focusing on the all-optical controllable scheme.
An all-optical scheme for OFRR was first proposed and experimentally demonstrated by Prof. Xinliang Zhang, Lecture Lei Shi and master student Yang Liu of Wuhan National Laboratory for Optoelectronics. Meanwhile, stability, repeatability and dynamic response of the device were systematically analyzed and tested. In this work, magnetic fluid is infused in a silica microcapillary and controlled by a pump light injected by a fiber tip, due to its strong photothermal effect. Eventually, the tunability for transmission spectra of the OFRR was realized. A tuning range of 3.3 nm and a tuning sensitivity of 150 pm/mW were achieved, with a good performance even at a very low pump power less than 1mW.
This work has been published in Lab on a Chip (Vol.14, No.16, pp.3004-3010, 2014), which is the best journal in the field of microfluidics. This work is partially supported by the National Natural Science Foundation of China (Grant Nos. 61125501, 61307075), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120142120067), and the Fundamental Research Funds for the Central Universities (HUST: 2014TS019).