578 research outputs found
Efficient oxide phosphors for light upconversion; green emission from Yb3+ and Ho3+ co-doped Ln(2)BaZnO(5) (Ln = Y, Gd)
This is the author's accepted version of the article. The final published article can be found here: http://dx.doi.org/10.1039/C0JM01652
Optical-resolution photoacoustic imaging through thick tissue with a thin capillary as a dual optical-in acoustic-out waveguide
We demonstrate the ability to guide high-frequency photoacoustic waves
through thick tissue with a water-filled silica-capillary (150 \mu m inner
diameter and 30 mm long). An optical-resolution photoacoustic image of a 30 \mu
m diameter absorbing nylon thread was obtained by guiding the acoustic waves in
the capillary through a 3 cm thick fat layer. The transmission loss through the
capillary was about -20 dB, much lower than the -120 dB acoustic attenuation
through the fat layer. The overwhelming acoustic attenuation of high-frequency
acoustic waves by biological tissue can therefore be avoided by the use of a
small footprint capillary acoustic waveguide for remote detection. We finally
demonstrate that the capillary can be used as a dual optical-in acoustic-out
waveguide, paving the way for the development of minimally invasive
optical-resolution photoacoustic endoscopes free of any acoustic or optical
elements at their imaging tip
Modelization and optimized speckle detection scheme in photorefractive self-referenced acousto-optic imaging
International audienceA photorefractive BSO single crystal can be used for axially resolved acousto-optic imaging of thick scattering media in absence of a reference beam. This configuration renders the experimental setup easier to realize for imaging through thick scattering media with an improved optical etendue. We present here a model and simulations that explains these results. It is based on the spatial heterogeneity of the speckle pattern incident on the crystal. Optimization of the detector position and of the speckle grain size is confirmed by the model
Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5
Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 109, 063104 (2011) and may be found at
Spatiotemporal pulses in a liquid crystal optical oscillator
A nonlinear optical medium results by the collective orientation of liquid
crystal molecules tightly coupled to a transparent photoconductive layer. We
show that such a medium can give a large gain, thus, if inserted in a ring
cavity, it results in an unidirectional optical oscillator. Dynamical regimes
with many interacting modes are made possible by the wide transverse size and
the high nonlinearity of the liquid crystals. We show the generation of
spatiotemporal pulses, coming from the random superposition of many coexisting
modes with different frequencies
Optical-resolution photoacoustic microscopy by use of a multimode fiber
We demonstrate Optical-Resolution Photoacoustic Microscopy (OR-PAM), where
the optical field is focused and scanned using Digital Phase Conjugation (DPC)
through a multimode fiber. The focus is scanned across the field of view using
digital means, and the acoustic signal induced is collected by a transducer.
Optical-resolution photoacoustic images of a knot made by two absorptive wires
are obtained and we report on resolution smaller than 1.5{\mu}m across a
201{\mu}m by 201{\mu}m field of view. The use of a multimode optical fiber for
the optical excitation part can pave the way for miniature endoscopes that can
provide optical-resolution photoacoustic images at large optical depth.Comment: 10 pages, 3 figure
Contrast manipulation and controllable spatial filtering via photorefractive two-beam coupling
A scheme is presented that achieves passive controllable spatial filtering via two-beam coupling in BaTiO3, between a reference beam and the optical Fourier transform of an input image. The nature of the spatial filtering is determined by the intensity dependent gain seen by each component of the Fourier transform. By appropriate choice of intensity ratio, the operations of contrast enhancement, feature extraction, and defect enhancement are possible, and representative examples of these are given
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