Three - University of Arkansas Physics Department

Biennial IEEE International Nonvolatile Memory Technology Conference, p 66-67,1998
Nonvolatile Optical Storage In Photorefractive Crystals
Gregory J. Salamo, Matt Klotz, and Hongxing Meng
University of Arkansas
Physics Department, Fayetteville, Arkansas 72701
phone: (50 1)575-593 1
fax: (501)5754580
salamo@comp.uark.edu
Richard J. Anderson
National Science Foundation
4201 Wilson Boulevard, Suite 875, Arlington, Virginia 22230
phone: (703)306-1683
fax: (703)306-0456
rjanders@nsf.gov
Christy A. Heid, Brian P. Ketchel, Gary L. Wood
U.S. Army Research Laboratory
AMSRL-SE-EO, 2800 Powder Mill Rd., Adelphi, MD 20783-1 197
phone: (301)721-3408
fax: (301)72 1-3400
cheidaarl .mil
light in a bulk material is an old dream suddenly come me.
Abstract
Several types of onedimensional (ID) and two-dimensional
We discuss the stateof-the-art for Wca1
(2D) bright or dark spatial solitons or waveguides
storage of information in photorefractive crystals. In
-
have recently been demonstrated experilnentally. All of these
mcular, we have been successhrl in 3-D
occur when ae diffraction of a light beam is exactly balan&
images and ten micron optical interconnects.
by the nonlinear self-focusing effect for bright solitons or
is a common technique used to generate
self-defocusing effect for dark solitons. In this sense the
realistic three-dimensional images. Photorefractive crystals
induces its own waveguide and oEms the to
are an 'Orage for holo~a~hic guide, steer, and switch another optical beam, We now
images because of the following advantages: real-time
picture light beams controlling light beams as one beam
e-swe and display, simpler recording process in which no
induces a waveguide whch guides, and even deflects a
pre- or post-processing is required, low writing beam powers, beam. Another possibility is four fibers on each side
and a potentially large *Orage Recent
of a crystal and soliton or self-indued waveguide formation
have clearly demonstrated the potential of photorefractive allowing interconnects betwen them.
for storage and of
Intuitively, one way to view the formation of a waveguide is
images. In this paw, we report the first demonstration, to by picturing a focused laser beam passing an
our knowledge, of the corresponding storage and retrieval of electrically biased photorefractive crystal. a result of the
three-dimensional color holograms in a photoref'ractive
laser carriers are excited and are transported to the
crystal. The three-dimensional image reproduces the colors
peripheral of the beam, screening the applied field in the
Of 'le object and is visible Over a wide perspective as
illuminated region. Therefore, the applied voltage creates an
demonstrated by moving one's head back and forth while
electric field primarily in the dark regions, whereas the
viewing the
The wide field-of-view of. the
electric field in the bright region is considerably lower, Sine
hologram is also demonstfated using an lens with a the index change created by the linear elfftro+ptic/effect is
color CCD camera mounted on a goniometer to record
proportional to the electric field, the index is lowered
various perspectives.
primarily in the dark region and a graded-index waveguide is
In addition to storage of 3-D images we have also been
created that mimics the laser intensity distribution, This
successm at
Of
index profile leads to trapping of the beam and the formation
waveguides or optical interconnects in bullr
Or
of an individual screening spatial photorefractive soliton.
potential substrates for electronic applications. Using the
While this trapping has applications when volatile we have
power in a light beam itself to form long narrow needles of
0-7803-4518-5198 $10.00 01998 IEEE 66 1998 Int'l Nonvolatile Memory Technology Conference