Xuqiang Wu

Optimization of a fiber optic flexible disk microphone

An optimized design of a fiber optic flexible disk microphone is presented and verified experimentally. The phase sensitivity of optical fiber microphone (both the ideal model with a simply supported disk (SSD) and the model with a clamped disk (CLD)) is analyzed by utilizing theory of plates and shells. The results show that the microphones have an optimum length of the sensing arm when inner radius of the fiber coils, radius and Poissons radio of the flexible disk have been determined. Under a typical condition depicted in this paper, an optimum phase sensitivity for SSD model of 27.72 rad/Pa (-91.14 dB re 1 rad/μPa) and an optimum phase sensitivity for CLD model of 3.18 rad/Pa (-109.95 dB re 1 rad/μPa), can be achieved in theory. Several sample microphones are fabricated and tested. The experimental results are basically consistent with the theoretical analysis.

A fiber-optic flexural disk microphone of high sensitivity

A fiber-optic flexural disk microphone is developed to detect acoustic signals in the air. It consists of a Mach-Zehnder interferometer with an optimized sensing arm of 7.93 m. The disk’s resonance frequencies and their influence on the microphone’s sensitivity are investigated. The microphone’s frequency response is measured in the frequency range from 100 Hz to 5 kHz and the average phase sensitivity is about -120.7 dB re 1rad/μPa.

High-efficiency one-dimensional atom localization via two parallel standing-wave fields

We present a new scheme of high-efficiency one-dimensional (1D) atom localization via measurement of upper state population or the probe absorption in a four-level N-type atomic system. By applying two classical standing-wave fields, the localization peak position and number, as well as the conditional position probability, can be easily controlled by the system parameters, and the sub-half-wavelength atom localization is also observed. More importantly, there is 100% detecting probability of the atom in the subwavelength domain when the corresponding conditions are satisfied. The proposed scheme may open up a promising way to achieve high-precision and high-efficiency 1D atom localization.

An improved PGC demodulation algorithm of interferometric sensor for eliminating the intensity disturbance

A modified phase generated carrier (PGC) demodulation algorithm for interferometric sensor is presented in this letter. Compared with the differential-cross-multiplying measure (PGC-DCM algorithm), the effect of light intensity disturbance (LID) is eliminated. Additionally, the harmonic distortion of arctangent measure (PGC-arctan algorithm) is well suppressed. In the experiment, while the simulated LID frequency is settled to 50 Hz, the signal-to-noise of the improved PGC algorithm respectively receives an increase of 10.3 dB and 18.2 dB over PGC-DCM and PGC-Arctan algorithms. The system has a dynamic range of 45.9 dB at 600 Hz by employing the improved PGC demodulation algorithm.

Efficient two-dimensional localization effect in a semiconductor quantum well

The behavior of the two-dimensional (2D) localization effect is explored by monitoring the excitonic population in a three-level semiconductor quantum well under the action of two orthogonal standing-wave fields. Owing to the position-dependent quantum interference, the localization behavior is significantly improved due to the joint quantum interference induced by the standing-wave and pumping fields. Most importantly, the electron can be localized at a particular position and the maximal probability of finding the electron in one period of the standing-wave fields reaches unity by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve a high-precision and high-resolution 2D localization effect in a solid.

Design of a novel vibration sensor based on Mach-Zehnder interferometer

Because of a series of advantages such as high sensitivity, non-contact measurement, interferometric vibration sensors have attracted interest from a lot of researchers in vibration sensing field. In this paper, a novel Mach-Zehnder interferomtric vibration sensor which utilizes quadrature detection technology is proposed. In our system, non-polarized light source and 1/4 wave plate is used to obtain two in-phase and quadrature-phase (I/Q) signals. Compared with previous methods, this sensor system has a simple optical configuration and more reliable stability. Theoretical analysis indicates that this sensor can measure the vibration displacement accurately.