Three-wave nonlinear interactions of space charge waves in thin n-GaAs fdm, possessing the negative differential mobility, are simulated. An effective frequency upconversion with amplification in millimeter wave range is demonstrated. The Poisson's equation and the set of quasi-hydrodynamic equations have been simulated by the finite difference method. An influence of transverse inhomogeneity io the plane of the fdm on three-wave interaction in active medium has been investigated.
We propose an experimental efficient optical pressure sensor based on a variable liquid lens and a modified point diffraction interferometer. The working principle of the sensor is based on the fact that a variation in pressure induces a change in lens curvature and hence in its focal length, which can be tracked and measured with the interferometer. The pressure is then measured by recording and processing the interferometric images. The sensor in this proposal can change its dynamic range by the simple axial movement of one of the components of the optical system. In this work we show the performance of the system within three working ranges: from 0 to 1 kPa with accuracy of approximately 0.01 kPa, from 0 to 7 kPa with 0.05 kPa accuracy, and from 0 to 30 kPa with 0.3 kPa accuracy.
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