Liquid Crystal-Based Geometric Phase-Enhanced Platform for Polarization and Wavefront Analysis Techniques with the Short-TeraHertz FEL Oscillator TerRa@BriXSinO

Abstract

In this work, we propose to design a liquid crystal–based modular and extendable platform of cutting-edge optical technologies for studying materials based on the analysis of polarization and wavefront of light in the wavelength range of 10–50 μm, which is considered to work even in the longer wavelengths range. This platform will be driven by the future THz-FEL source TerRa@BriXSinO that produces high power radiation in THz-range from 6 THz up to 30 THz (Mid-/Far-IR). The lack of optical infrastructures in this range has been tackled by fabricating liquid crystal–based geometric phase components that have been specifically designed for this purpose. This is in order to optimally exploit all the source’s potential for maximum accuracy and efficiency in determining polarization- and wavefront-sensitive properties of materials. We present an overview of a few experiments for characterizing bulk inhomogeneities, dielectric anisotropy, surface roughness, cracks, impact damages, and stress and strain effects with special emphasis on non-destructive tests on composite structures. The tools for wavefront shaping developed within our platform will be exploited to add a further degree of freedom, i.e., orbital angular momentum, to nonlinear optics techniques, such as Terahertz Hyper-Raman spectroscopy, for investigating chiral agents’ properties.

Coherent Spontaneous Emission from Short Electron Bunches: Competition between Different Transverse Waveguide Modes

“…The generation of short ultra-broadband (several wave cycles) terahertz (THz) electromagnetic pulses with high peak fields is an important problem from the point of view of various applications of such pulses (see, e.g., [1][2][3][4][5][6][7][8][9]). A well-known way to produce powerful coherent radiation is the use of various (undulator, cyclotron, Smith-Purcell) types of emission from relativistic high-current electron beams together with the use of the Doppler up-conversion of the electron oscillation frequency to achieve sub-THz and THz frequency ranges.…”

Terahertz unipolar polarimetry by second-harmonic generation in air

“…These beams exhibit varying spatial polarization and intensity distributions, and their significance in future THz photonic devices and applications is expected to increase over time, mirroring the trend observed in the visible range. 23,24 To measure these characteristics by means of TUP, a straightforward approach involves scanning the focus of the probe beam across the transverse plane of the THz beam, where the size of the THz beam in the focus is significantly larger than the probe beam's waist. Figure 5(e) illustrates a vector beam with a radial distribution of linear polarization, while Fig.…”