Femtosecond pulse generation in photonic crystals
Supervisors: Dr. Chad Husko, Prof. Ben Eggleton
Contact: husko@physics.usyd.edu.au
Femtosecond optical pulses play a critical role across a broad range of physics disciplines.
From basic research into spectroscopy, atomic clocks, and frequency combs, to arbitrary
waveform generation and telecommunications, these ultrafast events attract interest from
both fundamental and applied perspectives.
You will build on the first experimental observation of temporal pulse compression in
photonic crystals, recently published in Nature Photonics [Colman, Husko et al], to generate
femtosecond pulses with precisely tuned properties in photonic crystals. Photonic crystals are
the optical equivalent to electronic semiconductors, such as silicon, that pervade our daily
lives. A photonic crystal is made by ‘drilling’ a series of air holes in a thin slab of dielectric
material. These periodic media possess amongst the largest nonlinear and dispersion
properties of known optical materials. Moreover, one can modify the photonic crystal
structure to precisely tune these properties.
You will begin by modelling the pulse propagation with the nonlinear Schrodinger equation,
then using simulation software to design nanophotonic structures with the desired properties,
and finally characterizing their designs in the CUDOS lab.
Black holes and the all-optical transistor: what do they have in common?
Supervisors: Dr. Chad Husko, Prof. Ben Eggleton
Contact: husko@physics.usyd.edu.au
From black holes, to oceanic ‘rogue’ waves capable of swallowing ships, replicating the
physics of ‘big things’ in the lab is challenging. Fortunately the laws of nature have parallels
in other disciplines, presenting the opportunity to explore more complex systems in a
controlled fashion. Over the past few years, experimental analogues of optical Rogue Waves
and optical Event Horizons associated with black holes have been demonstrated in the lab,
allowing for deeper physical insight into their large-scale counterparts for the first time.
The goal of this project is demonstrate an optical event horizon in a tiny photonic crystal.
Photonic crystals are periodic media with feature sizes (< 200 nm) at sub-wavelength
dimensions. The optical event horizon relies on a nonlinear optical effect known as crossphase modulation (XPM), e.g. one beam controlling the phase of another beam. Moreover,
this remarkable phenomenon has recently been proposed as an all-optical transistor. You will
employ the unique nonlinear properties of the photonic crystal to demonstrate this
phenomenon over micron length scales, opening the possibility of truly integrated optical
transistors. You will begin by modelling the underlying physics with numerical software,
then using simulation software to design nanophotonic structures with the desired properties,
and finally characterizing their designs in the CUDOS lab.
Mid-IR Bragg gratings written in chalcogenide As2S3 fibers by a transverse holographic
technique (experimental)
EIE Supervisor: A/Prof. Javid Atai
javid.atai@sydney.edu.au
Supervisors: Prof. Ben Eggleton, A/Prof. Stuart Jackson, Dr. Irina Kabakova
ben.eggleton@sydney.edu.au, stuart.jackson@sydney.edu.au, kabakova@physcis.usyd.edu.au
Fiber Bragg grating, 1D periodic structure in the core of the fiber, is an important building
block for fiber-optic devices and systems, which has been used in telecommunications for
filtering, sensing and dispersion management for over 20 years. Bragg gratings at mid-IR
wavelength (above 2 μm) aren’t commercially available and represent an attractive
opportunity to broaden a limited range of fiber-optic components and functionalities in midIR, a spectral range of high interest for defence and medical applications. Up to date there is
only one demonstration of Bragg gratings in mid-IR by using a phase-mask technique, a
method that does not allow tunability of the grating resonance. In this project we propose to
use a different method, so-called transverse holographic technique, to inscribe Bragg gratings
at mid-IR wavelengths in chalcogenide fibers. Such a fabrication technique provides
flexibility of the resonant wavelength and is one of the most versatile methods for grating
inscription.
The target Bragg wavelength is 2.9 μm and corresponds to the central wavelength of a
tuneable Holmium fiber laser, which has been developed in our laboratory and is proposed in
this project for characterization. The grating is expected to be written in a single-mode
chalcogenide As2S3 fiber with a diameter of 136 μm. The fiber exhibits guidance at 2.9 μm
according to modelling and our experimental measurements. The writing setup is based on a
2nd harmonic of Nd:YAG laser (λ=532 nm). Bragg gratings at 1550 nm inscribed in
chalcogenide fibers by means of this setup have been demonstrated in our laboratory
previously. This makes our project to be a feasible and natural transition towards mid-IR
region. Achieving good quality Bragg gratings at 2.9 μm will open numerous opportunities
and applications of this system towards high-sensitivity sensing and mid-IR fiber lasers.
Computer generated holography techniques for future optical telecommunication
networks
Supervisors: Prof. Ben Eggleton, Dr. Jochen Schroder, Dr. Joel Carpenter
This project endeavours to exploit the as yet largely unexplored spatial dimension of optical
communications to increase the bandwidth of telecommunication systems.
The available capacity of optical fibre systems is rapidly approaching its theoretical limits.
Light has but a finite number of properties and with amplitude, phase, polarisation and
wavelength almost fully exploited there is but one remaining degree of freedom available :
space. Using the spatial dimension of light will be essential if future communications systems
are going to continue to keep pace with the world’s appetite for increased capacity. Space
Division Multiplexing (SDM) represents a radical shift in fibre communications and although
it will be vital for future networks, it is a largely unexplored area full of exciting research
opportunities. This work is part of an industry collaboration between the University of
Sydney and industry partner Finisar which seeks to leverage Finisar’s existing technology for
applications in SDM through the use of holographic techniques to control the way light is
coupled into and out of multi-core and multimode fibres to increase capacity and build the
systems which will be required as part of future networks.