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"In our lab we prepare laser-cooled atomic samples at temperatures of a
few microKelvin to investigate the spatial transport of ultracold
atoms at sub-micron scales. We expect to observe interesting effects
such as non-Brownian random walks and quantum tunneling. We also
dabble in developing novel optical sensors for ultrasensitive
bioimaging."
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Description of Research
We have a broad experimental program investigating the spatial
transport and mutual radiative interactions of cold atoms in optical
lattices. An optical lattice
comprises cold atoms organized in
crystal-like fashion in periodic potential
wells induced by the interference of
several laser beams. The depth D, shape,
and spacing 'd' of the wells can be
adjusted by varying laser intensity,
polarization, and frequency (Fig. 1).
Specifically our twin goals are to
investigate in an optical lattice -
a) Non-Brownian Random walks
and Quantum Tunneling:
Typically the trapped atoms in an optical lattice undergo Brownian
motion between lattice sites (Fig. 1). Interestingly, when the wells
are shallow, the atoms are predicted to undergo a random walk
fundamentally different from Brownian motion. On the other hand, in
the deep well limit, atom transport is expected to proceed by quantum
tunneling between adjacent wells. We aim to observe these effects.
b) Radiation Trapping:
This refers to the re-absorption (or ``trapping") of incoherent
spontaneously emitted photons inside an atomic sample irradiated with
coherent laserlight. Sensitive detection of radiation trapping is
important in the context of building cold atom-based quantum
Regarding our interest in optical sensors we have invented a novel
device which measures real-time changes in the refractive index of
fluids with a sensitivity of one part-per-million. We are applying
this device to biological and environmental sensing.
The student-researcher's role in this lab
Our cold atom setup incorporates over 200 state-of-the-art optical
components, and an array of electronics, lasers, ultrahigh vacuum
systems, magnetic field configurations, and ultralow level light
imaging systems. Most of the experimental setup, including the lasers,
is home-built, for the relevant commercial technology does not exist.
Undergraduate and Master's students who spend two or more years in the
lab (including summers) may expect to gain expertise in building
frequency-tunable diode laser systems, ultrahigh vacuum systems, and
sophisticated electronics for temperature/frequency-control of the
lasers, performing detailed optical alignments of fibers and
state-of-the-art devices such as acousto-optic deflectors and optical
valves, and machining with the mill and lathe.
In addition to the experiment, we also do a lot of our own theory.
Nowhere in all the sciences is there a greater need to understand the
precise mathematical principles behind natural phenomenon than in
physics. This is especially true in fundamental physics where
empirical notions, no matter how ingenious, are simply not credible.
Research in our lab teaches the student physicist-in-training the
theoretical ability to predict new fundamental phenomena in optical
and atomic physics, and critically assess fundamental predictions made
by others.
Undergraduate accomplishments in our lab
An undergraduate who has
had two semesters of introductory physics (PHY181/182, for example)
can begin work in my lab. My entire lab was put together by a core
group of four undergraduate students. In the past six years, I have
mentored a total of sixteen undergraduates in my research lab,
resulting in eight appearances by Miami undergraduates as co-authors
on refereed publications, and four research presentations themselves
by Miami undergraduates at external
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