Optical tweezers are of particular interest in various fields of science and technology such as atomic physics, nanotechnology and micromechanics. Today, there are many devices for manipulating microscopic objects using optical tweezers. In comparison with the most of known manipulation systems, the acousto-optic deflection is characterized by higher speed, the possibility to control several optical traps independently, high-precision movement of the trap within the field of view. In optical tweezers, longitudinal movement of micro-objects is also required. For this, special optical systems with variable characteristics, may be used. In this paper, we propose to combine these two approaches in one setup for 3D manipulation, i.e. to use acousto-optic scanning, using Bessel optical beams and an optical variosystem designed for longitudinal movement of the Gaussian beam waist at its constant diameter.
Optical tweezers use a special class of light beams – the so-called Bessel beams. The field amplitude of these beams is described by the Bessel function of the first kind of a zero order. The traditional method of forming zero-order Bessel beams involves the use of a classical optical element – a conical axicon lens. We designed and assembled an experimental test bench to study the parameters of the Bessel beam formed by the axicon. In the course of experimental studies, it was confirmed that Bessel beam is a diffraction-free beam. In addition, an influence of a divergence of the Gaussian beam at the axicon input on the parameters of the Bessel beam was investigated. The transformation of such a beam by an optical system was considered. It is shown that when the Bessel beam is transformed by an optical system, the principle of similarity of optical fields in the optical conjugate planes is fulfilled. The results of modeling the formation of the Bessel beam by the axicon obtained in this work are consistent with the experimental studies.
This paper presents features of synthesizing the optical system of lidar transmitting channel subject to the specificity of laser radiation. Examples of different types of laser optic systems of dimensional synthesis are presented.
De-noising of terahertz (THz) pulsed spectroscopy (TPS) data is an essential problem, since a noise in the TPS system data prevents correct reconstruction of the sample spectral dielectric properties and to perform the sample internal structure studying. There are certain regions in TPS signal Fourier spectrum, where Fourier-domain signal-to-noise ratio is relatively small. Effective de-noising might potentially expand the range of spectrometer spectral sensitivity and reduce the time of waveform registration, which is an essential problem for biomedical applications of TPS. In this work, it is shown how the recent progress in signal processing in wavelet-domain could be used for TPS waveforms de-noising. It demonstrates the ability to perform effective de-noising of TPS data using the algorithm of the Fast Wavelet Transform (FWT). The results of the optimal wavelet basis selection and wavelet-domain thresholding technique selection are reported. Developed technique is implemented for reconstruction of in vivo healthy and deseased skin samplesspectral characteristics at THz frequency range.