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Miami University
Dr. Samir Bali

Associate Professor
Department of Physics
Phone: 513-529-5635
Fax: 513-529-5629

Dr. Samir Bali
Dr. Samir Bali "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."

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


$100.000 Grant from the State of Ohio
Nanomaterials in our Environment

$100.000 Grant from the State of Ohio
Nanomaterials in our Environment

Nano is HUGE at Miami University
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