Experimental studies of laser light intensity profiles, with light propagation direction perpendicular to the optical c-axis, in ferroelectric single crystal fibers such as LiNbO3 are carried out and reported. Theoretical simulations of such multimode propagation of light are also conducted for the LiNbO3 single crystal fibers. The simulation and experimental studies are extended to and compared with the commercially available single mode and multimode silica optical fibers. Theoretical simulations provided a good account for the light intensity profiles measured and led to a preliminary interpretation of complex specklegram observed in anisotropic single
crystal fibers.
Recently, we proposed a new speckle-based hologram multiplexing recording
technique. In this method, a multi-mode LiNbO3 single crystal fiber is employed to
generate speckle patterns which are used as reference beams in hologram recording
process. The compact modulation architecture of this new technique allows a fiber
array structure which can dramatically increase the system storage capacity as well as
realize image adding function. To explore the functionality and the performance of a
fiber array structure, a dual-fiber configuration has been set up in our laboratory and
the preliminary experimental results are presented in this report.
Piezoelectric resonance contributions to the electrooptic coefficients in ferroelectric PZN-8PT single crystals were
studied by a dynamic electrooptic measurement carried out using a continuous frequency scan over the range of
frequency covering the sample's fundamental resonances. At certain frequencies relevant to piezoelectric resonance of a
given mode, it is found that the E-field modulated optical transmission are greatly enhanced (> 2 orders of magnitude).
Such enhancement is mode selective and scales with strain or the rate of change of dielectric permittivity. Instead of
having linear dependence on the electric field, the piezoelectric resonance enhanced optical transmitted signal in this
crystal shows a near linear response to the power of the modulating electric field.
Recently, we proposed a new speckle-based hologram multiplexing recording technique. In this method, a multi-mode LiNbO3 single crystal fiber is employed to generate speckle patterns which
are used as reference beams in hologram recording process. The speckle pattern generation can be precisely controlled by external
E-field. Theoretically, this technique can generate thousands of
decorrelated reference beams at given practical constraints. The system storage capacity has so far been estimated based on idealized settings. As it is well known that, besides the limitation set by the
modulation mechanism capacity the storage density of a volume hologram memory system can be also restricted by many other factors. Among all factors, the crosstalk is a fundamental one that may
ultimately put a tighter bound to system storage capacity. This paper is devoted to the theoretical analysis and numerical simulation of crosstalk in this proposed technique.
A zinc oxide (ZnO) single crystal microtube fabricated by using an encapsulated microwave-heating growth
method has been reported. This microtube has a highly symmetrical hexagonal tubular structure, and exhibits
strong near-band-edge emission, highly selective UV light response, and excellent electron field emission. In this
paper, we study the converse piezoelectric properties of the microtube by using a sensitive modified Michelson
laser interferometer. The experimental results demonstrate that this hexagonal hollow structure has very
interesting piezoelectric properties compared with bulk ZnO crystals.
Besides the well-known LiNbO3, ferroelectric strontium barium niobate (SBN) crystals are attractive
for electrooptic modulation applications because of their high electrooptic coefficients and low half wave voltage.
Their EO properties, typically obtained under low frequency electric field driving conditions, contain both primary
and secondary contributions arising from electromechanical coupling. Single crystal fibers (Sr,Ba)Nb2O6 and
LiNbO3 grown by laser heated pedestal growth method are investigated to explore the frequency dependence of
electrooptic property both for mechanically stress-free crystals (low frequency) and at microwave driving frequency
of 10GHz. An optical pulse can be up-tuned/down-tuned, squeezed/ expended in the range of GHz using a single
piece of SBN crystal fiber under a moderate microwave field, controlled by the relative position of optical pulse
traversing the crystal fiber to the microwave field. The effective microwave-photonic interactions demonstrated in
ferroelectric SBN crystals provide a potential solution for the bandwidth definitions and wavelength tuning
applications. The experimental configuration and the analysis are also of general significance in electrooptic
property studies at microwave frequencies.
In this paper, a new speckle based hologram multiplexing recording technique is proposed and tested. In
this method, a multi-mode LiNbO3 single crystal fiber is employed to generate speckle patterns which are
used as reference beams in hologram recording process. The speckle pattern generation can be precisely
controlled by external E-field. Theoretically, this technique can generate thousands of decorrelated
reference beams at given practical constraints. Its storage capacity can be scaled up as material properties
are improved, making it well adapted to new material development. A theoretical analysis and numerical
simulation of speckle pattern generation are also presented in this paper.
In electro-optic (EO) modulator devices ferroelectric crystals of strontium barium niobate (SBN) are attractive due to exceptional high EO coefficients and low half wave voltage. SBN single crystals grown by laser heated pedestal growth are investigated to explore frequency dependent EO property at low frequency and near resonant frequency range. The mechanism of its frequency dependence is discussed briefly.
A new method of phase-coded multiplexing is proposed and tested. The construction of this multiplexing scheme combines a rotating cylindrical-collimating lens system (RCCLS) with a random phase transparent mask. It is verified that such a system is capable
of storing over 1000 images in a doped LiNbO3 crystal. Experimental results and theoretical analyses presented in this paper demonstrate that a compact, all optical, secure and high capacity volume holographic memory system can be implemented with further exploitation
of the method.
Hetero-core fiber structure consists of a sandwiched structure of fibers with different core diameters. Hetero-core fiber structure has found its application in both intensity based and phase change based sensors. In this paper, an analysis of hetero-core fiber structure in photonic crystal fibers (PCF) and waveguides is presented. With the finite-difference time-domain (FDTD) method, the performance of such a structure in a fiber specklegram sensor and the refractive index modulation on PCF section are investigated. It is found that the unique photonic nanostructures can substantially enhance the sensitivity of the specklegram sensor with added dynamic range tunability, which can lead to many practical applications in optical sensors.
Thermal electron dynamics at the interfaces of thin gold film/ferroelectric lithium niobate (LiNbO3) is studied by using step-function type laser irradiation. Our measurements reveal an anomalous transient optical transmission fluctuation caused by thermal electron dynamics at the interfaces. To our knowledge, such phenomenon and its theoretical explanation haven't been reported.
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