Quantitative Analysis Method and Correction Algorithm Based on Directivity Beam Pattern for Mismatches between Sensitive Units of Acoustic Dyadic Sensors.

Acoustic dyadic sensors (ADSs) are a new type of acoustic sensor with higher directivity than microphones and acoustic vector sensors, which has great application potential in the fields of sound source localization and noise cancellation. However, the high directivity of an ADS is seriously affected by the mismatches between its sensitive units. In this article, (1) a theoretical model of mixed mismatches was established based on the finite-difference approximation model of uniaxial acoustic particle velocity gradient and its ability to reflect the actual mismatches was proven by the comparison of theoretical and experimental directivity beam patterns of an actual ADS based on MEMS thermal particle velocity sensors. (2) Additionally, a quantitative analysis method based on directivity beam pattern was proposed to easily estimate the specific magnitude of the mismatches, which was proven to be useful for the design of ADSs to estimate the magnitudes of different mismatches of an actual ADS. (3) Moreover, a correction algorithm based on the theoretical model of mixed mismatches and quantitative analysis method was successfully demonstrated to correct several groups of simulated and measured beam patterns with mixed mismatches.

Design and Optimization of Sensitivity Enhancement Package for MEMS-Based Thermal Acoustic Particle Velocity Sensor.

In this paper, small-sized acoustic horns, the sensitivity enhancement package for the MEMS-based thermal acoustic particle velocity sensor, have been designed and optimized. Four kinds of acoustic horns, including tube horn, double cone horn, double paradox horn, and exponential horn, were analyzed through numerical calculation. Considering both the amplification factor and effective length of amplification zone, a small-sized double cone horn with middle tube is designed and further optimized. A three-wire thermal acoustic particle velocity sensor was fabricated and packaged in the 3D printed double cone tube (DCT) horn. Experiment results show that an amplification factor of 6.63 at 600 Hz and 6.93 at 1 kHz was achieved. A good 8-shape directivity pattern was also obtained for the optimized DCT horn with the lateral inhibition ratio of 50.3 dB. No additional noise was introduced, demonstrating the DCT horn's potential in improving the sensitivity of acoustic particle velocity sensors.

Modulated vortex six-wave mixing.

We have experimentally generated a vortex six-wave mixing (SWM) signal via a photonic band gap structure in a hot atomic ensemble. The output SWM carrying orbital angular momentum, transferred from a probe beam, has the interaction with the nonlinear effect in the multilevel atomic system. Our results show that a spatial SWM image can be modulated by the detunings and intensities of the related generating fields. Also, the nonreciprocal feature of the SWM signal is demonstrated. Such characteristics can potentially be used in information processing.

Correlation and squeezing for optical transistor and intensity router applications in diamond NV center.

We study an optical transistor (switch and amplifier) and router by spontaneous parametric four-wave mixing and fluorescence in diamond nitrogen-vacancy (NV) center. The routing results from three peaks of fluorescence signal in the time domain, while the switching and amplification are realized by correlation and squeezing. The intensity switching speed is about 17 ns. The optical transistor and router are controlled by the power of incident beams. Our experimental results provide that the advance technique of peak division and channel equalization ratio of about 90% are applicable to all optical switching and routing.