High-precision microdisplacement sensor based on zeroth-order diffraction using a single-layer optical grating

Temperature-robust optical microphone with a compact grating interferometric module

The high demand for advanced acoustic sensors has prompted optical microphones to become a current research hotspot; this is especially the case in light of the performance of existing electroacoustic microphones having reached the ceiling. In this work, a thermally stable optical microphone has been developed for sensitive detection of low-frequency acoustic signals. The microphone was prepared using a prestressed nickel diaphragm and a compact grating interferometric module. The adjacent surfaces of the diaphragm and grating form a short Fabry-Perot cavity, which makes the microphone robust to ambient temperature fluctuation due to the reduced thermal drift of its operating point relative to the quadrature point of the interferometer. The cavity length-operating wavelength relationship of the microphone operating at the quadrature point was obtained. The performance of the prepared microphone was tested using various methods. Experimental results show that the microphone enables stable operation at the quadrature point over a wide range of temperatures from 0°C to 60°C with low signal distortion and high sensitivity. The response of the prepared optical microphone to low-frequency drone noise was measured and compared with that obtained with a commercial electret condenser microphone.

Hardware optical correlation method for dynamic detection of micrometer gaps with sub-nanometer resolution

Surface plasmon lithography breaks through the diffraction limit with surface plasmon effect and achieves high-resolution imaging below sub-wavelengths. The dynamic detection and control of the working distance between the mask and the substrate is particularly important for the quality of the lithography samples. In this paper, the mask-substrate gap sensing mechanism is analyzed, and a mask-substrate gap absolute distance measurement model is established based on the principle of white light interference. We design a Fizeau interferometer demodulation system based on a hardware optical correlation method, and focus on analyzing the influence of the sub-nanometer surface profile of the optical wedge on the resolution. Finally, we propose a data processing method for extracting the dynamic gap value by SSA (singular spectrum analysis). The experimental results show that the system shows high performance with a gap detection range of 3.0∼6.0 µm, the stability of ±0.12 nm, and the resolution of better than 0.30 nm.

Micro-opto-electro-mechanical systems accelerometer based on the Talbot effect of double-layer diffraction gratings

In this paper, we present the design, fabrication, and test of a micro-opto-electro-mechanical systems (MOEMS) accelerometer based on the Talbot effect of double-layer diffraction gratings. The detection of acceleration is realized by using the highly sensitive displacement characteristic of Talbot imaging of near-field diffraction with double-layer gratings. For the purpose of obtaining optimal contrast of the optical interferometric detection, the parameters of the gratings are optimized by the finite-difference time-domain (FDTD) simulation. The experimental results indicate that this MOEMS accelerometer with the proposed design can achieve a resolution of 246 µg, sensitivity of 6.1 V/g, and bias stability of 0.02 mg. The proposed accelerometer can be operated at higher accelerations (∼80g), which shows significant potential for being used in applications that require detection of strong and fast vibrations, especially in vibration sensing of vehicles and geophysical seismic sensing in real time.

High-precision micro-displacement sensor based on tunnel magneto-resistance effect

A high-precision micro-displacement sensor based on tunnel magneto-resistance effect is reported.We designed and simulated magnetic characteristics of the sensor, and employed chip-level Au-In bonding to implement low-temperature assembly of the TMR devices. We employed the subdivision interpolation technique to enhance the resolution by translating the sine-cosine outputs of a TMR sensor into an output that varies linearly with the displacement. Simultaneously, using the multi-bridge circuit method to suppress external magnetic and geomagnetic interference. Experimental result shows that the micro-displacement sensor has a resolution of 800 nm, accuracy of 0.14\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document}% and a full-scale range of up to millimeter level. This work enables a high-performance displacement sensor, and provides a significant guide for the design of a micro-displacement sensor in practical applications.

Single-detecting-path high-resolution displacement sensor based onself-interference effect of a single submicrometer grating

On the basis of the self-interference effect between ±1 st-order diffraction beams from a single optical submicrometer grating, we demonstrate a single-detecting-path optical displacement sensor with high resolution. Using a quadrant optoelectronic detector, a single-detecting-path system without any wave plates is realized experimentally. Combined with an interpolation circuit, we demonstrate the system for displacement measurement within a range of 200 µm. The results indicate a detecting sensitivity of 905.4°/µm and an accuracy of ±1.9µm. It is worth mentioning that, considering a maximum subdividing factor of 9674 used in experiment, the resolution goes down to 41.1 pm in principle. We demonstrate a compact optical sensor with high resolution, which is promising in developing miniaturized displacement systems.

Micro-opto-electro-mechanical gyroscope based on the Talbot effect of a single-layer near-field diffraction grating

We demonstrate a novel, to the best of our knowledge, micro-opto-electro-mechanical system (MOEMS) gyroscope based on the Talbot effect of a single-layer near-field diffraction grating. The Talbot effect of an optical grating is studied both theoretically and experimentally. A structure of grating-mirror combination, fabricated by the micro-nano processing method, is used for out-of-plane structure detection. The detection of a weak Coriolis force is realized by using the highly sensitive displacement characteristic of Talbot imaging of near-field diffraction with a mirror mass block and single-layer grating. The experimental results show that, the micro-displacement detection sensitivity can reach up to 0.09%/nm, and the MOEMS gyroscope can be moved in the driven direction, with a resonant frequency of 7048 Hz and a quality factor of 700, which indicates great potential of the Talbot effect in developing novel high-performance micro-gyroscopes.