Optical Science and Engineering ETDs

Publication Date

Summer 7-11-2018

Abstract

The mid-infrared (2-14 μm) spectral region contains the strong absorption lines of many important molecular species, which make this region crucial for several well-know applications such as spectroscopy, chemical and biochemical sensing, security, and industrial monitoring. To fully exploit this region through absorption spectroscopic techniques, compact and low-cost narrow-linewidth (NLW) mid-infrared (MIR) laser sources are of primary importance.

This thesis is focused on three novel compact NLW MIR lasers: demonstration and characterization of a new glass-based spherical microlaser, investigation of the performance of a novel fiber laser, and the design of a monolithic laser on a silicon chip. Starting with fabrication of spherical microcavities based on MIR transparent materials, I showed the feasibility of achieving quality factors of more than 10 million in whispering- gallery mode (WGM) microresonators made of different types of fluoride glasses. Next using Erbium doped ZBLAN glass spherical microresonators, I demonstrated a new ultra- low threshold NLW MIR microlaser. In particular, all aspects of this room temperature continuous-wave (CW) microlaser with a wavelength of 2.71 μm are carefully characterized and studied and the origin of the measured mode structure and polarization is described using a simple analysis. To amplify the output power of this laser, I designed and fabricated a MIR fiber amplifier with a record gain of about 30 dB at 2.71 μm that facilitated the characterization process and boosted the MIR power level to usable level while preserving the laser linewidth.

To demonstrate the application of MIR microresonators and microlasers, I studied intracavity absorption spectroscopy based on active and passive high quality WGM MIR microlasers and microresonators. I also estimated the sensitivity and detection limit of gas sensors based on these devices. The outcome of my analysis shows that ppm level sensitivity should be achievable using both active and passive microresonators.

Next, I modeled the performance of two newly proposed configurations for NLW MIR generation based on stimulated Raman scattering. First, I studied a new family of Raman fiber lasers that are capable of generating any NLW MIR line in the 2.5-9.5 μm spectral region. I demonstrated the feasibility of this MIR laser family, calculated the threshold conditions, identified the condition for its single-mode operation, and laid the foundation for the first experimental demonstration of such lasers. Finally, I explored the performance of silicon-based on-chip Raman lasers and the parameters that have prevented expanding their wavelength to MIR range. Using the outcomes of this study, I proposed and then analyzed a new architecture for on-chip silicon Raman lasers capable of generating single NLW lines around 3.2 μm with sub-mW threshold pump power.

Degree Name

Optical Science and Engineering

Level of Degree

Doctoral

Department Name

Optical Science and Engineering

First Committee Member (Chair)

Mani Hossein-Zadeh

Second Committee Member

Ravinder K. Jain

Third Committee Member

Jean-Claude Diels

Fourth Committee Member

Ganesh Balakrishnan

Document Type

Dissertation

Language

English

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