29.4.15

You are invited to attend a lecture

By

Oshrit Hakoon

(MSc. student under the supervision of Prof. Avraham Katzir and Dr. Yoav Sintov)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Samarium doped silica fiber as a pump source protection and as a saturable absorber in all-fiber-self-Q-switched laser

Over the last decade, there has been a remarkable increase in powers produced by fiber lasers, steeper than that shown by their bulk solid-state counterparts. These increased power levels are leading to a rapid penetration of fiber systems into applications formerly dominated by other lasers. In most fiber lasers, the lasing medium is a rare-earth (RE) doped silica fiber. In the development and fabrication process of such silica fibers, the spectral properties of the RE doped glass can be modified by using different co-dopants.

At the center of my thesis stands the analysis and development of a new Samarium (Sm) doped silica fiber designed to achieve two purposes:

Our first goal was to protect a 1018nm pump fiber laser source in a high power fiber laser operating at 1070-1080nm, from back reflections and stray-light. Samarium (Sm), which exhibits an extinction ratio of ~15 between the two relevant wavelengths, was a natural choice for our application. A comprehensive theoretical study motivated the choice of Phosphor (P) as a co-dopant, and established the physical and geometrical design of the protecting fiber. The designed fiber was manufactured, and was analyzed using a variety of experimental techniques and setups. It was found that the fiber provides excellent protection to the pump source, and that it is durable and stable under high power regime.

Our second goal was to demonstrate the use of the designed fiber as a saturable absorber in an all-fiber self-Q-switched Yb laser. Despite their many advantages, relatively few configurations of fiber lasers were Q-switched so far. In most cases, Q-switched fiber lasers suffer from complexities of alignment, packaging, and maintenance. A passive all-fiber configuration allows to avoid these effects, and was therefore of particular interest. In this work, we successfully demonstrated utilization of the designed fiber as a saturable absorber in an all-fiber passively Q-switched ytterbium laser, operating in 1084nm. The laser produced pulse repetition rates of ~40-100kHz, pulse durations of ~ 1-2.5µsec, and pulse energies of up to 1.4 µJ. the experimental results are compared to simulative results, and the differences between the two are discussed.

Wednesday, April 29, 2015, at 12:00

Room 011, Kitot building.