Keywords

spectroscopy, mid-infrared, terahertz radiation, absorption, absorbance

Abstract

The optical frequency comb is a coherent light source whose spectrum consists of hundreds of thousands perfectly equidistant narrow frequency components and precisely expressed in just two radio frequencies. Even though optical frequency combs were developed 25 years ago, that led to the Nobel Prize in Physics 2005, only recently there was a significant progress in generating broadband optical frequency combs in the mid-infrared. These achievements became possible due to the development of new types of robust fiber and solid-state lasers and the efficient downconverting of their frequencies through different techniques based on advanced nonlinear crystals. In this dissertation, I study the techniques of producing ultra-broadband frequency combs in the challenging mid-infrared and terahertz regions of the electromagnetic spectrum. These combs find applications in high-precision molecular spectroscopy, atmosphere monitoring, reaction kinetics, and ultrasensitive trace gas detection to name a few. In addition, I investigate their application in the dual-comb spectroscopy, which is a tool involving two combs with slightly different comb line spacings that are interfered on a photodetector generating a radiofrequency comb. So, effectively high optical frequency is mapped to radiofrequency that can be easily recorded with available digital electronics. This method has a list of advantages over traditional spectrometers, namely broadband coverage combined with superior spectral resolution, high acquisition speed, high precision, and the absence of moving parts. Moreover, in the context of the experimental results, my spectroscopy investigations with low-pressure gases led to reliving a massive amount of spectroscopic data that had never been explored before, and some of which was already included into a global database. The results presented in this dissertation paves the way for creating highly accurate molecular spectroscopic databases and have the potential for real-time medical diagnostics through multi-species exhaled breath analysis.

Completion Date

2024

Semester

Spring

Committee Chair

Konstantin, Vodopyanov

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Format

application/pdf

Language

English

Rights

In copyright

Release Date

May 2024

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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