4 research outputs found
Incoherent white light solitons in logarithmically saturable noninstantaneous nonlinear media
We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam
Incoherent white light solitons in logarithmically saturable noninstantaneous nonlinear media
We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam
Engineering the nonlinear dynamics of photonic systems : demonstration of the soliton-similariton fiber laser and nonlinear laser lithography
Ankara : Materials Science and Nanotechnology Program of the Graduate School of Engineering and Science of Bilkent Univ., 2013.Thesis (Ph. D.) -- Bilkent University, 2013.Includes bibliographical references leaves 99-107.Nonlinear effects easily and unavoidably arise in ultrafast optics, often acting
as sources of limitation to performance. However, many fascinating phenomena,
from generation to utilization of ultrashort laser pulses rely on the very same
nonlinear effects. Deep understanding of the governing dynamics, coupled with
mechanisms through which they can be controlled or manipulated holds potential
for observing new phenomena, as well as achieving new functionalities, which can
be difficult or even impossible to achieve otherwise.
This thesis presents a series of work, starting from a novel mode-locked oscillator
for generating ultrashort pulses, followed by amplification of ultrashort pulses
to microjoule-level energies, finally a novel nanostructuring mechanism relying
on the nonlinear interaction of such pulses with the surface of a metal.
The novel mode-locked laser developed in this thesis is one in which pulses
propagate self-similarly in the presence of amplification, as similaritons, in one
part of the cavity and as soliton-like pulses in the rest of the cavity. The coexistence
of the seemingly incompatible similariton and soliton-like waves subject
to the boundary conditions of a laser oscillator requires in the presence of a narrow
bandpass filter and result in spectral breathing of the waves by unprecedented one
order of magnitude, constituting the observation of the strongest nonlinear effects
in any mode-locked laser to date. The laser reduces to the dispersion-managed
laser in limit of large filter bandwidth and to the all-normal-dispersion laser in
the limit of vanishing anomalous-dispersion fiber. Thus, all the four basic modelocking
regimes are covered. As such, we believe the unraveling of this regime
can be instrumental in deeper understanding of all the mode-locking regimes.
Importantly, by showing that two attractor solutions can co-exist in a single
laser cavity opens the door to new future designs. From an applications point of
view, the laser is easy to mode-lock and exhibits excellent short-term and longterm
stability, indicating high potential for high precision materials processing
applications.
We also illustrate, to our knowledge, the first high-energy, all-fiber implementation
of the nonlinear chirp pulse amplification technique, which allows us to
achieve in-fiber peak powers of 57 kW. We demonstrate a fiber amplifier with
no free space beam pump or signal beam propagation, producing 70-ps chirped
pulses with 3 μJ and 4 μJ pulse energies, which are compressible to 140 fs and
170 fs, respectively, via a grating compressor. The amplified output can be used
directly, as a picosecond source, or compressed externally in a grating compressor.
This approach results in a completely robust, misalignment-free system,
with peak powers approaching 10 MW. This was, at the time of publication, the
highest peak power obtained from an integrated fiber amplifier.
Finally, we apply the laser systems we developed, together with the lessons
learned from our implicit control of the nonlinear dynamics to demonstrate a
method that utilizes positive nonlocal feedback to initiate, and negative local
feedback to stabilize growth of self-organized metal oxide nanostructures, initiated
and controlled by ultrafast pulses. We achieve unprecedented uniformity at high
speed, low cost, and on non-flat or flexible surfaces. By exploiting the nonlocal
nature of the feedback to stitch the nanostructures seamlessly, we are able to cover
indefinitely large areas with sub-nm uniformity in periodicity. We demonstrate
our approach through fabrication of TiO2 and tungsten oxide nanostructures,
which can be extended in principle to a large variety of materials.Öktem, BülentPh.D
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High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays
This thesis describes the development of a new mid-infrared laser designed to drive high harmonic generation of keV-energy soft x-rays with high flux. The mid-infrared wavelength regime (3 to 5 μm wavelength) is required to generate high harmonics with photon energies reaching 1 keV in the form of isolated attosecond bursts. This light would provide simultaneous few-nanometer spatial resolution and attosecond time resolution that could shed light on physical processes which occur at these length and time scales. Such processes have both scientific and technological importance.The laser system described in this thesis reaches pulse energies up to 1.25 mJ at 1 kHz repetition rate, 3.1 μm wavelength, and with enough bandwidth to support 60 fs transform-limited pulses. Also, we demonstrate preliminary pulse compression to below 500 fs. This laser is therefore the first table-top mid-infrared laser with enough peak intensity and average power to generate harmonics with sufficient flux to be useful for application experiments. This laser uses Optical Parametric Chirped Pulse Amplification (OPCPA) to convert near-infrared light to the 3 μm wavelength regime, combining fiber lasers, cryogenically cooled solid state lasers, diode lasers, and optical parametric amplification in a unique architecture. In this thesis, we describe the current design of this laser system, the considerations that influenced its design, and its potential for scaling to higher pulse energies and repetition rates in the future