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

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

THz pulse generation in ZnGeP2 with near-IR pumping

THz wave generation was investigated in nonlinear ZnGeP2 crystals with the fs pumping at 800 nm and 950 nm. Transmission and absorption spectra were analyzed. Refractive indices of the ZnGeP2 in the THz range were measured and approximated in the form of Sellmeier equations. Phase-matching conditions were calculated. Calculated conditions are well correlated with experimental data

Millimetre-wave range optical properties of BIBO

We present the thorough studies of optical properties of BiB3O6 (BIBO) crystal in the millimeter-wave (subterahertz) range. We observe a large birefringence Δn = nZ −nX = 1.5 and the values of absorption coefficients of all three axes to be less than 0.5 cm−1 at the frequency of 0.3 THz. The difference from visible range in angle ϕ between the dielectric axis z and crystallophysical axis X is found to be more than 6°. The simulated phase-matching curves in the xz plane of the crystal show the optimal value of the angle θ to be around 25.5°±1° for an efficient millimeter-wave generation under the pump of 1064 nm laser radiation

The efficiency of THz wave generation in β-BBO under visible and IR fs pulse pump

Potential efficiency of the THz wave generation by down-conversion of the visible emission in nonlinear β-BBO crystal is estimated. Eight types of interactions are found possible. Four interaction types were realized in the carried-out experiments. Optical damage threshold under fs pumping was estimated

Doubling of THz radiation frequency in nonlinear borate crystals

The use of nonlinear oxide crystals for radiation generation and conversion into terahertz (THz) range using the nonlinear crystal optics methods is a new promising direction that has actively been developed in the last few years. For the first time, the possibility is considered of effective frequency doubling of millimeter radiation in the wavelength range of 400–2500 m in borate crystals. The phase matching angles are calculated. It is shown that o + o → e and e + o → e interactions can be realized in LN and β-BBO crystals, and only o + o → e interactions are possible in LB4 crystals. The walk-off angle and the spectral and angular matching bandwidths are calculated. The maximal efficiency of the second harmonic generation is estimated taking into account the measured optical damage threshold of 150 TW/cm2 for the LB4 crystal and 100 TW/cm2 for the β-BBO crystal. This shows advantages of application of the oxide crystal in the THz range of the spectrum