Technologies in the 2 µm waveband
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Date
2021-12
Authors
Russell, Eoin
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Publisher
University College Cork
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Abstract
Over the last couple of decades, photonic technologies have become an
integral part of many fields of scientific research and industry. Some of these
applications include, but are not limited to, optical communications,
metrology and optical sensing. As the field of photonics continues to mature
and develop, the diversity of its applications also expands. One of the keys to
maintaining this growth is the development of technologies that enable the
operation of photonic devices at different wavelengths. The near-infrared
waveband has been extensively studied due to its applications in the
telecommunications industry, mostly around the 1550 nm wavelength. When
looking further along the IR waveband the 2 μm wavelength region is of
particular interest due to its potential applications in the fields of optical
communications, silicon photonics and optical sensing.
In this thesis, we develop two technologies for enabling applications and
research in the 2 μm waveband. The first achievement was the realisation of a
semiconductor laser based frequency comb source at 2 μm. Optical combs are
becoming ubiquitous in research applications, from spectroscopy to carrier
generation for coherent optical communications. Beyond laboratory
application, optical combs have seen little implementation due to their cost,
size and complexity. In this thesis, we develop a compact and robust comb
source for the 2 μm waveband using recently developed InP based
semiconductor laser sources and the gain switching modulation method. In
addition to this, the first demonstration of a dual frequency comb was shown
at this wavelength. This allowed for the analysis of these combs using low
speed photodetectors at near real-time acquisition rates. The optical frequency
combs developed could be key components in enabling optical sensing and
metrology applications in the 2 μm wavelength region.
The second achievement of this thesis was the development of fibre amplifiers
for the 2 μm waveband using the rare-earth element Thulium (Tm3+). Due to
the relative immaturity of technologies at this wavelength, managing
component losses and maintaining optical power is essential. Thulium doped
fibre amplifiers (TDFAs) offer a broad amplification bandwidth ranging from
1650 nm-2150 nm. These amplifiers can be pumped using a variety of
wavelengths, each having their benefits and weaknesses which are explored in
this thesis. Through variation in pump wavelength and doped fibre length, amplifiers were developed which were optimised for wavelengths around 2 μm while utilising low pump power.
Description
Keywords
Photonics , 2 µm , Laser , Optical frequency combs , Dual frequency combs , 2 µm waveband , Optical spectroscopy , Gain switching , Laser pulse generation , Thulium doped fiber amplifier , Fiber amplifier , Multi-quantum well laser
Citation
Russell, E. 2021. Technologies in the 2 µm waveband. PhD Thesis, University College Cork.