Abstract
Nanostructures have been widely applied on superhydrophobic surfaces for controlling the wetting states of liquid microdroplets. Many modern optic devices including sensors are also integrated with micro- or nanostructures for function enhancement. However, it is rarely reported that both microfluidics and optics are compatibly integrated in the same nanostructures. In this paper, a novel microfluidic-controlled tunable filter composed of an array of periodic micro/nanopillars on top of a planar waveguide is proposed and numerically simulated, in which the periodic pillars endow both the Bragg grating and the superhydrophobic functions. The tunability of grating is achieved by controlling the sagging depth of a liquid droplet into the periodic pillars. Simulation results show that a narrow bandwidth of 0.4 nm and a wide wavelength tuning range over 25 nm can be achieved by such a microfluidic-based tunable optofluidic waveguide Bragg grating filter. Moreover, this proposed scheme can be easily modified as a refractive index sensor with a sensitivity of 103 nm per refractive index unit.
Highlights
Tunable optical filters have a vast variety of applications such as wavelengthmultiplexers in optical networks, reflectors in optical switchers and tunable lasers, etc
They can be realized with many different mechanisms including whispering gallery mode (WGM) resonators [1], Mach–Zehnder interferometers [2], fiber Bragg gratings [3], Fabry–Perot microcavities [4], and waveguide Bragg gratings [5]
The waveguide Bragg grating has attracted a great deal of interest due to its easy integration with various device platforms, such as silicon-on-insulator (SOI), silica planar lightwave circuits (PLC), indium phosphide monolithic and Bloch surface wave (BSW) platforms
Summary
Tunable optical filters have a vast variety of applications such as wavelength (de)multiplexers in optical networks, reflectors in optical switchers and tunable lasers, etc. Through some kinds of external external as gaselectrowetting, pressure, electrowetting, etc., sagging into the cavities forces, suchforces, as gas such pressure, etc., [12,13,14,15,16], the[12,13,14,15,16], saggingthe depth intodepth the cavities can be can be dynamically controlled, which is equivalent to modulating the refractive index of the ambient dynamically controlled, which is equivalent to modulating the refractive index of the ambient media for the waveguide Bragg grating, leading to a tunable optofluidic filter.
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