Ytterbium doped all-fiber integrated high power laser systems and their applications
Author
Yılmaz, Saniye Sinem
Advisor
İlday, F. Ömer
Date
2013Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
For the past decades, high-power laser technology has been developing rapidly
all over the world. The scientific interest in fiber lasers stems from the rich nonlinear
dynamics. Industrial interest is largely due to their practical advantages,
such as high power levels, compact size, relatively low cost, excellent beam quality,
over established laser technologies. As a result, fiber laser are highly sought
after in applications including material processing, especially in high-precision
micromachining with ultrafast pulses, medical applications and defence applications,
especially for the high power and efficiency levels that fiber laser can
offer. The advantage of fiber lasers for high powers is largely due to their geometry,
which is a very long cylinder, with an extremely high surface to volume
ratio, rendering heat transfer away from the active medium much easier. Fiber
lasers diffraction-limited beam quality if operating in the fundamental fiber mode.
Average output powers that can be extracted from singlemode fiber lasers can
reach up to a few kilowatts without serious thermal problems due to the fiber
structure. For many realworld applications, misalignment free operation is important
and an all-fiber laser system offers this prospect, but to date, most of the
published reports on high-power lasers utilise bulk optics components to couple
light in and out of fibers, which detracts from some of the practical advantages
of fiber lasers. Ytterbium doped fibers which are preferred as active media for
high-power operation, as the technology behind it has led to the development
of excellent components and the small quantum defect is extremely useful for
high-power applications. Yb-doped continuous wave lasers practically can reach
several kilowatt levels, yet the output power of Yb-doped picosecond and sub
picosecond pulsed lasers with a small count of bulk optics in the cavity have been
limited to several hundred watts. In this thesis, we mainly focus on developing two high-power, robust, fiberintegrated
lasers systems. The first system is a laser designed for continuous-wave
(cw) operation, reaching up to 200 W level. The second system is a picosecondpulsed
system, delivering 100-W, few-ps pulses at 100 MHz repetition rate. The
latter is built based on master oscillator power amplifier (MOPA) structure. The
multi-stage amplifier of the pulsed system and resonator design for the continuous
wave laser system are both based on the all-fiber designs which allow for robust
operation and have been optimised through numerical simulations. We expect
these systems to find widespread use in material processing applications.
Keywords
fiber laserhigh power laser system
ablation
ytterbium doped fiber laser
ultrafast ablation