Optical Science and Engineering ETDs

Publication Date

Summer 7-1-2020


Over the past decades, high-power fiber lasers and amplifiers have been extensively under research to achieve higher output powers. However, temperature rise in the core of fiber lasers and amplifiers has been a big issue in power-scaling. Radiation-balancing is a viable technique introduced for effective heat mitigation in lasers and amplifiers by S. Bowman in 1995. Radiation-balancing relies on solid-state laser cooling as a self-cooling mechanism to mitigate the generated heat in lasers and amplifiers. To implement the mentioned idea in fiber lasers and amplifiers, a set of issues should be scrutinized; (i) the amenability of silica glass (as the most common host material in optical fibers) to laser cooling and (ii) an efficient design for implementing radiation balancing in the fiber laser or amplifier.

For a radiation-balanced laser or amplifier, the gain medium should be amenable
to laser cooling; therefore, the observation of laser cooling in silica glass is a
necessary step. In this study, to the best of our knowledge, for the first time we
report the first observation of laser cooling in silica glass. We will show a
temperature drop of 0.7 K below ambient in a Yb-doped silica fiber preform.
Our analyses also show that due to the small doped area of (Double-Clad) DC
fibers, radiation-balancing cannot effectively mitigate the generated heat in
moderate-power operation regime; therefore, a new configuration that we name
"Core/Cladding ion-doped configuration" is introduced to enable the DC fiber
amplifiers to mitigate the generated heat in moderate-power operation regime.

Degree Name

Optical Science and Engineering

Level of Degree


Department Name

Optical Science and Engineering

First Committee Member (Chair)

Dr. Arash Mafi

Second Committee Member

Dr. Mansoor Sheik-bahae

Third Committee Member

Markus P. Hehlen

Fourth Committee Member

Dr. Akimasa Miyake

Fifth Committee Member

Dr. Ganesh Balakrishnan


Lasers, Amplifiers, Solid-state laser cooling, Optical fibers

Document Type