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of Physics Laser
Physics
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Projects
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Research Projects in Laser Physics
Please view the description of ongoing research and contact the researchers directly for more detailed information on a project to suit you.
Coupling of self-assembled quantum dots to microsphere cavities.
The aim of this project is to explore possible applications of coupling self assembled PbS/CdS quantum dots [1] to high Q whispering gallery modes in glass microspheres [2]. In particular, we wish to explore the possibility of coupling, and hence entangling the quantum states, of two dots attached to the same sphere. Such an arrangement could constitute a 2-qubit quantum computer [3].
[1] anything on our dots?
[2] M.V. Artemyev et al, Nanoletters 1, 6, 309-314 (2001)
[3] T.A. Brun and H. Wang, quant-ph/9906025 8 Jun 1999
Absolute Measurement of Optical Torques and Forces
Optical forces and torques can be exerted on microscopic particles leading to many applications, particularly in cellular biology. Since the forces and torqes arise through the exchange of linear and angular momentum between the particle and the beam, it is in principle possible to deduce the force or torque from measurements of the deflection or change in polarisation respectively of the trapping beam. [1,2] The aim of the project is to develop and implement practical schemes for achieving this and making a critical comparison with conventional methods. Opportunities exist to make tests on real biological systems such as cell membranes.
[1]
[2]
Dynamics of micro-BEC in wire guides
It has recently been shown [1] that a Bose Einstein Condensate (BEC) can be rather easily produced in a a magnetic atom trap formed near a surface carrying an array of microlithographically formed wires. Already techniques have been developed to move atomic clouds around such an 'atom chip' [2]. The aim of the project is to examine the internal dynamics in a BEC being moved around for various applications. It forms part of a program concerned with quantum dynamics of atoms [3]
[1]
[2]
[3] Nature
Lasing without inversion and slow light using cold
Rubidium atoms
Supervision: Prof Halina Rubinsztein-Dunlop, Assoc Prof Norman Heckenberg, Dr Zbigniew Ficek (theory), Dr Marlies Friese (lab work)
Objective:
· To observe lasing without inversion in a L type system, realized in
85Rb atoms cooled and confined in a magneto-optical trap
· To measure the extremely steep dispersion about the atomic transition
resulting from the above effect.
Project Background:
In 2001, we worked on pump/probe spectroscopy in cold 85Rb atoms, aiming at
measurement of the absorption of a probe laser beam by the cold atom cloud,
as it was scanned through the 85Rb 5S1/2 F=3 - 5P1/2 F=3. The absorption signal
is modified by the presence of a pump laser beam at the 5S1/2 F=2 - 5P1/2 F=3
transition.
Our latest results include the observation of electromagnetically induced transparency
(EIT), which occurs when an atomic transition probed by a weak laser becomes
transparent to photons that would normally be absorbed. This effect results
from quantum interference.
Theory predicts that the application of an additional weak incoherent field
in our system can result in amplification of the probe laser beam (lasing without
inversion). The aim of this experiment is to observe this effect.
Another interesting property of the system is the extremely narrow linewidth
of the EIT peak, which can be narrower than a natural atomic linewidth. Such
narrow spectral features have associated with them extremely sharp dispersion,
and very high refractive index peaks close to the transition frequency. The
fast change in refractive index leads to slowing down the probe beam group velocity.
We will also aim to make a measurement of the dispersion about the probe atomic
transition.
Existing theory will be modified to model the 85Rb system.
Methods/techniques involved in the project:
Experimental
· Operation of grating feedback diode lasers and Ti-S laser
· Laser trapping and cooling of 85Rb
· Precision timing of experiment using Labview and other GPIB control
Theory
· Master equation of the system
· Group velocity of light and its dependence on the refractive index
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Department
of Physics, The University of Queensland |
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