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Title

THz beam shaping through laser filamentation engineering

Alternative Title

Διαμόρφωση ακτινοβολίας THz μέσω του ελέγχου της διαδικασίας νηματοποίησης λέιζερ

Author

Παππά, Δήμητρα

Thesis advisor

Τζωρτζάκης, Στέλιος

Abstract

Terahertz (THz) beam profile shaping has an essential role in an extensive spectrum of scientific, industrial, and technological applications, among them high-resolution imaging, spectroscopic analysis, advanced communication systems, and material processing. Classical methods for modifying the THz beam profile, such as diffractive optical elements, metasurfaces, and wavefront phase manipulation, have proven beneficial; nevertheless, they tend to be associated with supplementary system complexity or losses of power. In this present study, we suggest a novel approach for controlling the shape and the energy distribution of a broadband THz beam by manipulating the THz source directly. In our experimental setup, ultrashort laser pulses (800 nm, 35 fs, 2 mJ/pulse, 1 kHz) and their second harmonic deliver a typical two – cοlor laser filamentation process in air, which produces THz radiation. To shape the THz beam, we use a Spatial Light Modulator (SLM) that operates at the initial laser frequency and produces diverse laser energy distributions. By creating off-axis spherical phases, the SLM allows the development of different laser filaments across multiple spatial arrangements. This technique enables us to alter the classical doughnut – shaped THz beam profile that results from a single filament, leading to additional complicated beam profiles when two or more filaments are positioned in varied geometries. The method we developed provides the entire electronic control of the beam profile by employing phase masks on the SLM, resulting in dynamic and adaptable THz beam shaping. When the filaments are significantly separated, the resulting beam profiles can be attributed to either linear interference effects or nonlinear energy redistribution through Kerr cross – talk when the filaments are sufficiently close to one another. This all – optical approach, recognized for its straightforwardness and simplicity of execution, presents promising applications in THz imaging and beam engineering, notably in the field of telecommunications. Our outcomes illustrate that by directly controlling the laser – induced filamentation process, we can obtain flexible and efficient manipulation of THz beam shaping, setting up potential opportunities for the development of advanced THz technologies.

Language

English

Issue date

2024-11-21

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Graduate theses

Type of Work--Graduate theses

Permanent Link

https://elocus.lib.uoc.gr//dlib/8/8/2/metadata-dlib-1727248637-59819-27275.tkl

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