Ming Xuan

Mie Scattering-Enhanced Fiber-Optic Refractometer

A kind of biconically-tapered optical fiber (BTOF) modified by silica nanospheres is proposed to implement detection of refractive index (RI), especially low RI, with strong nonlinearity and enhanced sensitivity; this idea arose from an interesting experiment with a BTOF whose surface was very rough. The mechanisms of the nonlinear characters are investigated and explained by the coupling effects of Mie scattering and multimode propagation, and this phenomenon is repeated in several experiments with different fibers. Measured sensitivity magnification of more than 100 from a 2.8-μ.m-thick and 14-mm-long BTOF after modification by 400-nm silica nanospheres is shown in this letter.

Dynamic optimization of valveless micropump

For the first time, this paper reports on an effective topology optimization method to improve the output net flux for valveless micropumps. The micropump considered here is actuated by the vibration of membranes and can generate a net flow along the optimized rigid fluidic channel. The detailed layout of the micropump channel is optimized with respect to a number of factors which influence the output net flux of liquid, such as the number of actuation elements, the positions of actuation elements, the driving phase differences and the driving frequency. Accordingly, the layouts of several novel valveless micropumps are presented.

A Multi-Parameter Decoupling Method with a Lamb Wave Sensor for Improving the Selectivity of Label-Free Liquid Detection

The anti-symmetric modes (A01 mode for low frequency, A03 mode for high frequency) and symmetric modes (S0 mode) produced by Lamb wave sensor are used to detect multi-parameters of a liquid, such as its density, sound velocity and viscosity. These modes are found to be very different to the parameters. For example, the A01 mode is very sensitive to the liquids density but the A03 mode is sensitive to its sound velocity. The measurements of the attenuation with S0 mode can give out liquids viscosity after its density been determined by A01 mode. That could be a way to distinguish an unknown liquid with high sensitivity or to solve the problem of the selectivity of label free detection on biosensors.

Tuning response range of a transmission-based fiber-optic refractometer through LP11 mode

A kind of sensing scheme is theoretically proposed to efficiently tune the response range of a fiber-optic refractometer based on the adiabatic transmission of the higher-order LP11 mode. Near the cut-off condition, transmission of the LP11 mode is a strong function of the refractive index (RI) under detection; thus high sensitivity is achieved. The cut-off RI value is dependent on the waist diameter; therefore the response RI range with high sensitivity can be changed just by altering the waist diameter. Theoretical calculations reveal that the response range is effectively tuned from 1.43-1.438 to 1.35-1.365 when the waist diameter is reduced from 2.5 to 1 μm. The proposed fiber-optic sensor is also superior when used as an absorbing sensor since the higher-order mode LP11 has a much larger power fraction in the evanescent field compared with the fundamental mode LP01 of the same fiber.

Silica nanospheres for filtering higher-order optical fiber modes

Tapered optical fibers (TOFs) modified by 400 nm-diameter silica nanospheres have been experimentally and theoretically investigated. Responses of the modified TOFs (MTOFs) to methylene blue (MB) solution and surrounding refractive index (RI) have been compared. The higher-order modes are effectively filtered by the silica nanospheres, which is visualized by the interferometric output spectrum of the MTOF. The higher-order mode filtering makes the MTOF respond to MB solution with reduced sensitivity, which endows the MTOF with the potential for distinguishing the RI property from the absorption property of the molecules under detection.

Multi-parameters decoupling method with Lamb wave sensor for improving the selectivity of label-free liquid detection

The anti-symmetric modes (A 01 mode for low frequency, A 03 mode for high frequency) and symmetric modes (S 0 mode) produced by Lamb wave sensor are used to detect multi-parameters of a liquid, such as its density, sound velocity and viscosity. These modes are found to be very different to the parameters. For example, the A 01 mode is very sensitive to the liquids density but the A 03 mode is sensitive to its sound velocity. The measurements of the attenuation with S 0 mode can give out liquids viscosity after its density been determined by A 01 mode. That could be a way to distinguish an unknown liquid with high sensitivity or to solve the problem of the selectivity of label free detection on biosensors.