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.
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.
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 ferroelectric single crystal fiber placed inside a microwave cavity is designed to perform pulse uptuning, downtuning, or reshaping by utilizing chirping effects on optical pulses traversing through it. For electrooptic modulator devices ferroelectric crystal fibers are of significant interest due to their high electrooptic coefficients and near-circular cross-sectional waveguide configuration. Single crystal fibers of strontium barium niobate grown by the laser heated pedestal growth method are shown to have high sensitivity to microwave electromagnetic field. Quantitative exploration for the influence of chirping on the performance of this modulator in a microwave cavity waveguide is carried out and reported.
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.
The application of ferroelectric crystals in light modulation has been of significant interests due to their exceptional electrical field sensitive optical properties or high electrooptic coefficients. Single crystal fibers of lithium niobate and strontium barium niobate grown by laser heated pedestal growth method are explored for optical pulse engineering (frequency shift, pulse compact, or pulse reshaping). The electrooptic behavior was investigated and compared in a microwave cavity of TE103 mode at 10GHz.
Although multimode fiber has a large space-bandwidth product (roughly equal to the number of modes), transmitting spatial signals by using a fiber is rather difficult. Conventional sensing schemes for fiber chemical sensors are based on the intensity and/or spectroscopic absorption or emission of fiber evanescent field of multimode fiber. However, the transmission of spatial signal has not been exploited in the field of chemical sensing. In our research, a novel chemical sensing method that employs the spatial information of a multimode fiber was investigated. When a laser beam is launched into a multimode fiber, the exit light field produces a complicated speckle pattern caused by the modal interference of the fiber. It is difficult to recover the transmitted information from the speckle field. However, the fiber speckle field can be used for fiber sensing with an inner product method. Our analysis and experiments have shown that the fiber specklegram sensor is very sensitive to chemical environment change.
Optical wavelength shifting is studied using ferroelectric single crystal electrooptic fibers subjected to electric field of microwave frequencies. Sr1-xBaxNb2O6 single crystals grown by the laser heated pedestal growth technique were tested and compared. The design and verification of the photon acceleration process and the exploration of the materials properties corresponding to growth, orientation and doping condition are presented.
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