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Design and Development
of Compact Spectrometers I and my colleagues have designed and developed a new class
of optical devices that integrates the functionalities of different optical
elements into a simple volume hologram. As a result, very compact, low cost
and easy to use devices such as portable spectrometers can be made with
particular applications in biological and environmental sensing. In such a
spectrometer, several optical elements of the conventional spectrometers
(such as an input slit, a collimating lens, a diffractive grating, and a
collector lens) are replaced by a specially designed volume hologram. This
work attracted much attention and was published as a newsbreak in Photonics
Spectra (April 2006) and in Advanced Materials and Processes (April
2006). |
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Diffraction Analysis of Complicated Holograms (Multi-grating
Method) To implement the functionalities of several optical
elements into a complicated volume hologram, I have developed a new
semi-analytic tool called multi-grating method. In this method, the
complicated hologram is represented as the superposition of several sinusoidal
gratings. The diffracted beam is then obtained by coherent superposition of
the diffracted components from each grating. Using this method and for the
first time, I derived a complete closed-form representation of the diffracted
beam from a spherical beam volume hologram that is valid for both near-field
and far-field scenarios. |
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Software-based Stabilized Holographic Recording I and my colleagues have developed and implemented a simple and low cost
stabilized holographic recording system based on a modular software design in
LabView. The stabilized recording system is necessary for long holographic
recording to completely characterize doubly doped crystals. Fringe stability
better than 1/20 of the wavelength of the recording beams was obtained for
more than 5 hours using our system. Based on these accurate holographic
recordings, I showed, for the first time, that the sensitivity (S) in two-center recording is a
function of the ratio of the recording to sensitizing intensities and not the
absolute intensities. |
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Global Optimization for Two-center Holographic Recording I performed a global optimization of dynamic range (M/#) and sensitivity (S) for two-center holographic
recording for the first time. I derived analytic formulas for M/#
and S for the recording phase of
the hologram and analytic and numerical solutions for the read-out phase. This
complete set of accurate solutions was derived for the first time and was necessary
for the global optimization. Using optimal design parameters, one order of
magnitude improvement for M/# and
more than two orders of magnitude improvement for S were obtained compared to the reported values before this work.
I also showed that a trade-off exists between M/# and S that should
be taken into account for the design of the optimum material. |
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