Abstract-Spatio-temporal and spatiospectral metrology of terahertz broadband uniformly topologically charged vortex beams

Maksim Kulya, Varvara Semenova, Andrei Gorodetsky, Victor G. Bespalov, and Nikolay V. Petrov

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-5-A90

A comprehensive characterization of the diffraction properties of terahertz (THz) pulsed broadband vortex beams consisting of several electromagnetic field oscillations requires state-of-the-art techniques for studying the evolution of a wavefront as it propagates. For this purpose, we have applied the capabilities offered by THz pulse time domain holography. Accurate metrological study of pulsed single-period THz field propagation allowed us to reveal the spatio-temporal and spatiospectral couplings in broadband uniformly topologically charged vortex beams. Here, we reveal dynamics of such beam propagation in a free space as well as in the experiment with edge diffraction with 50% blocking of the beam focal waist. In this study, we compare the dynamics of freely propagating and edge-diffracted THz vortex. Despite the fact that in the amplitude representation one can observe the emergence of strong asymmetry, analysis of the spectral trajectory of the singular point at some distance from the obstacle and the visualization of phase distribution for individual spectral components testify to the conservation of transverse energy circulation. Similar to the edge diffraction of monochromatic optical vortices, it can be interpreted as self-reconstruction of vortex properties. The given term has not previously been used for the case of pulsed broadband THz beams, to the best of our knowledge.

© 2018 Optical Society of America

Abstract-Wireless Data Transmission Method Using Pulsed THz Sliced Spectral Supercontinuum

Yaroslav V. Grachev,  Xinrui Liu, Sergey E. Putilin,  Anton N. Tsypkin,   Victor G. Bespalov,  Sergei A. Kozlov, Xi-Cheng Zhang

https://ieeexplore.ieee.org/document/8119558/

A method of ultrafast wireless information transmission using spectrum-sliced supercontinuum (SC) along the THz frequency range is presented in this letter. The THz spectrum-sliced SC was formed by femtosecond optical pulses doubled in a Michelson interferometer before being input onto a MgO:LiNbO3-THz generator. Two THz pulses generated by femtosecond pulses within a MgO:LiNbO3-crystal provided the spectrum-sliced SC in the spectral domain, which was recorded by an electro-optical detection system. The transmission rate in this method is determined by the bandwidth of the THz spectrum, the number of spectral lines in the SC, and the pulse repetition rate. We have demonstrated an SC containing 31 spectral lines with 23-GHz spacing within the range from 0.04 to 0.75 THz. The signal with encoded information was successfully transmitted over 2.4 m in free-space.

Abstract-On terahertz pulsed broadband Gauss-Bessel beam free-space propagation

Maksim S. Kulya, Varvara A. Semenova, Victor G. Bespalov, Nikolay V. Petrov,

https://www.nature.com/articles/s41598-018-19830-z

Terahertz pulse time-domain holography is the ultimate technique allowing the evaluating a propagation of pulse broadband terahertz wavefronts and analyze their spatial, temporal and spectral evolution. We have numerically analyzed pulsed broadband terahertz Gauss-Bessel beam’s both spatio-temporal and spatio-spectral evolution in the non-paraxial approach. We have characterized two-dimensional spatio-temporal beam behavior and demonstrated all stages of pulse reshaping during the propagation, including X-shape pulse forming. The reshaping is also illustrated by the energy transfer dynamics, where the pulse energy flows from leading edge to trailing edge. This behavior illustrates strong spatio-temporal coupling effect when spatio-temporal distribution of Bessel beam’s wavefront depends on propagation distance. The spatio-temporal and spatio-spectral profiles for different spectral components clearly illustrate the model where the Bessel beam’s wavefront at the exit from the axicon can be divided into radial segments for which the wave vectors intersect. Phase velocity via propagation distance is estimated and compared with existing experimantal results. Results of the phase velocity calculation depend strongly on distance increment value, thus demonstrating superluminal or subluminal behavior.

Abstract-Wireless data transmission method using pulsed THz sliced spectral supercontinuum

 Yaroslav V. Grachev,  Xinrui Liu, Sergey E. Putilin, Anton N. Tsypkin,   Victor G. Bespalov,  Sergei A. Kozlov,   Xi-Cheng Zhang

http://ieeexplore.ieee.org/document/8119558/

A method of ultrafast wireless information transmission using spectrum-sliced supercontinuum (SC) along the THz frequency range is presented in this manuscript. The THz spectrum-sliced SC was formed by femtosecond optical pulses doubled in a Michelson interferometer before being input onto a MgO:LiNbO3 THz generator. Two THz pulses generated by femtosecond pulses within a MgO:LiNbO3 crystal provided the spectrum-sliced SC in the spectral domain, which was recorded by an electro-optical detection system. The transmission rate in this method is determined by the bandwidth of the THz spectrum, the number of spectral lines in the SC, and the pulse repetition rate. We have demonstrated a SC containing 31 spectral lines with 23 GHz spacing within the range from 0.04 to 0.75 THz. The signal with encoded information was successfully transmitted over 2.4 meters in free-space.