Prospects of controlling the propagation of high-power THz radiation by passive optical elements including 3D printed

Optical properties of different commercial plastics for fused deposition modeling 3D printing are defined at room temperature in the spectral range 0.2˗1.2 THz. We compare absorption coefficients and refractive index of ABS, PETG, and SBS printed 1-4 mm plates. Different types of optical elements for controlling high-power THz radiation are studied. A comparison is made of the efficiency of attenuation of linearly polarized THz radiation with homemade band-pass polarizers obtained by etching copper from a flexible polyimide substrate. Filters and polarizers created using 3D printing or by deposition of polymer matrix with magnetic particles under external field are cost-effective and can be easily changed or replaced. Comparison between plastic insets, filters based on magnetic particles, and polyimide film filters are made

Development of electrochemical sensor based on aptamer specific to lung cancer tumor marker

Electrochemical aptasensor is a sensor based on an indicator electrode covered with a layer of an aptamer that is able to bind target molecules with high specificity. In this work, DNA-aptamer LC-2108 specific to lung cancer tumor marker was immobilized onto the surface of golden screen-printed and disc electrodes. The electrodes were studied by conventional electrochemical methods–cyclic voltammetry and electrochemical impedance spectroscopy. The current increase and electron transfer resistance decrease were registered. It seems as if the aptamer presence facilitated the electron transfer through the electrode-solution boundary. As the possible reasons of such an unusual electrochemical behavior we proposed the unordinary or irregular structure of the aptamer layer on the Au surface or the specific electrochemical properties of the aptamer itself

Prospects of controlling the propagation of high power THz radiation by passive optical elements including 3D printed

Different types of optical elements for controlling high power THz radiation were studied. Controlling was performed utilizing amplitude modulation of the electric field and effective spatial modulation of the complex dielectric susceptibility in the volume of the THz filter. We make a comparison of attenuation efficiency of various options of 3D printed filters when ABS filament is mixed with perovskite microparticles. Another type of filter was obtained by the deposition of magnetic particles in the presence of an external magnetic field in a transparent polymer matrix. Industrial isotropic cut-off filters based on layered meta structures have also been investigated. A comparison is made of the efficiency of attenuation of linearly polarized THz radiation with homemade band-pass polarizers obtained by etching copper from a flexible polyimide substrate and industrial filters. Filters and polarizers created using 3D printing, or by deposition of polymer matrix with magnetic particles under external field, are attractive cost effective elements

Optical properties and potential of LB4 for THz wave generation

Optical properties of a Li2B4O7 (LB4) crystal are determined in the spectral range 0.2-1.6 THz. Dispersion of the refractive index components for o- and e-wave are approximated in the form of Sellmeier equations. They are subsequently used to determine the possible interaction types and to calculate the phase-matching angles to get THz waves by difference frequency generation. The damage threshold is determined as well as the coherence length for all possible types of three wave interactions under the pump by fs Ti: Sapphire laser pulses at 950 nm. The efficiency of the processes is estimated. Using trains of hundreds of pulses at 950 nm it was found to be 1.32 times of that for β-BBO crystal laser pump

Detailed study on optical properties of Li2B4O7 for down-conversion to millimeter waves

Optical properties of single axes Li2B4O7 (LB4) crystal are defined at room temperature in the spectral range 0.03˗0.5 THz. Dispersion of the refractive index components are approximated in the form of Sellmeier equations. Dispersion properties were used to determine phase-matching conditions for THz wave generation by collinear difference frequency generation processes. To the damage threshold under the pump by train of hundreds of 60 fs pulses of Ti:sapphire laser operating at 950 nm is found to be 250 TW/cm2, as well as the coherence length and efficiency of all possible types of three wave interactions are defined

Detailed study on optical properties of Li2B4O7 for down conversion to millimeter waves

For the first time, we measured the laser damage threshold of LB4 nonlinear crystal (≥ 10 TW/cm2) for an fs- (60 fs, 950 nm) pulses. Refractive index components for a THz range 0.15-1.6 THz were measured and carefully reapproximated in terms of Sellmeier dispersion equations. Using the equations and the measured optical breakdown threshold, the efficiency of THz radiation generation is estimated for all possible types of three wave interactions. For e–e → e type of interaction deff = (2d15 + d31)cos2sin + d33sin3, o–o → e type deff = d31sin, and for o–e → o type deff = d15sin. The angle at which the phase matching conditions are achieved for THz radiation generation at frequencies < 1.5 THz is ≤ 10. Small values of the phase matching angles and, accordingly, small values of effective nonlinear coefficients explain the lack of experimental studies on the THz generation. The extremely high optical breakdown threshold and high atmospheric transmission in the longwavelength part of the THz range overcompensate low efficient nonlinear coefficients of LB4. Which makes it prospective for long trace high sensitivity probing of the atmosphere composition and parameters

Development of an automated prototype of THz filter based on magnetic fluids

Many new investigation approaches or techniques that rely on THz radiation are emerging today. It requires the development of devices for controlling THz radiation characteristics intensity, polarization, spectral properties, etc. One of the promising approaches to the implementation of such devices is the use of ferromagnetic fluids. Earlier, the efficient operation of polarizers and non selective THz attenuators based on ferromagnetic liquids was demonstrated. The liquids used consisted of 5BDSR alloy particles obtained by the mechanical synthesis in a planetary mill or Fe particles obtained by the electric explosion, dispersed in synthetic engine oil. Magnetic fluids were controlled using an external magnetic field generated by Helmholtz coils. In this study, we propose a prototype of a THz filter based on previously developed ferromagnetic fluids. Filter consists of a quartz or polymer cuvette with a magnetic fluid, several Helmholtz coils and a control circuit. This device allows one to orient the magnetic particles and to create ordered structures in the form of extended clusters. As a result, physical properties of electromagnets were optimized for effective controlling of particle clusters; the control process itself was automated. Spectral properties in the THz range are studied for various filter states. For reliable continuous operations, the device was supplemented with a homogenization system, based on mechanical mixing or sonication. The developed device can be used as a polarizer or an attenuator for polarized radiation in the range of 0.3-3 THz

Induced absorption spectra of crystal violet in various solvents

The study of short-lived induced (singlet-singlet) and long-lived induced (in particular, triplet-triplet) absorption capacity of crystal violet (CV) in various solvents was carried out by the pump-probe method. Water, dimethyl sulfoxide, isopropyl alcohol, and ethyl alcohol were selected as solvents. The formation of triplet states in various CV solvents was revealed upon excitation by nanosecond radiation of the 4th harmonic of a Nd: YAG laser (wavelength 266 nm, average power –25.5 mV, repetition frequency –3Hz, pulse duration –10 ns, peak power –10-12 MW/cm2). It is shown that the spectrum of the induced CV absorption in ethanol contains two closely spaced bands at 400 and 485 nm. Short-lived and long-lived induced CV absorption in isopropanol at room temperature (λmax=400 nm) was recorded