Chuanyong Huang

Measurement of microwave electro-optic coefficient in Sr0.61Ba0.39Nb2O6 crystal fiber

A method is put forward to measure the linear electro-optic (EO) coefficient at high frequency using a light-coupled microwave cavity perturbation method of standing wave condition. The method is used to determine the EO coefficient of Sr0.61Ba0.39Nb2O6 (SBN) crystal fiber. The electro-optic coefficient r33 of SBN crystal fiber at 10 GHz is measured to be near 200(pm∕V), which is smaller than that measured at low frequency containing secondary contributions. This method is suitable for measuring the electro-optic property in a wide range of high frequencies depending on the availability of microwave cavity and suitable electronics.

Dielectric measurement of ferroelectric Sr0.61Ba0.39Nb2O6 single crystal fiber using cavity perturbation method

The nonlinear dielectric property of the ferroelectric Sr0.61Ba0.39Nb2O6 (SBN) crystal is essential to device application at various frequency ranges. The dielectric constant of the SBN single crystal fiber was investigated at x band microwave frequency using the resonant cavity perturbation method. It was found that compared with large and decreasing dielectric constant of SBN at low frequency, the dielectric property of the SBN crystal at x band frequency was smaller with similar value controlled by dipole orientation or atomic vibration.

A novel fiber chemical sensor using inner-product multimode fiber speckle fields

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.

Real-time observation of pulse reshaping using Sr0.61Ba0.39Nb2O6 single crystal fiber in a microwave cavity

Ferroelectric single crystal fiber Sr0.61Ba0.39Nb2O6 (SBN) is evaluated for optical pulse engineering in terms of wavelength shifting and pulse compression/expansion through nonlinear optical (Pockels) effect at microwave frequencies. The microwave–photonic interaction was investigated experimentally in a TE103 microwave cavity at 10GHz. It is shown that the frequency component of an optical pulse can be controlled effectively using the SBN single crystal in a microwave cavity without the need of contact electrodes or any interruption to the optical system. The technique may be utilized in several aspects of optical communications such as channel definition and security encoding of the signal, and shows potential for a range of optoelectronic applications.

Real time observation of domain reversal in cerium-doped Sr0.61Ba0.39Nb2O6 single crystal fibers

Domain configuration is of significant importance in utilizing ferroelectric single crystals such as strontium barium niobate (SBN) to design optoelectronic and nonlinear optical devices. This letter reports the real time observation of domain reversal in cerium doped SBN crystal fibers by electro-optic imaging microscopy. The SBN single crystal fibers studied were grown using the laser heated pedestal growth technique. The dynamic polarization switching behavior of SBN crystal fibers can be described as an antiparallel domain nucleation at low electric fields after a dormant period and a sideways growth of domain walls at higher electric field. These two different mechanisms result in the asymmetric current curve of domain switching dynamics.

Dielectric Behavior of Strontium Barium Niobate Relaxor Ferroelectrics in Ceramics and Single Crystal Fibers

Ferroelectric strontium barium niobate (SBN) single crystal fibers are fabricated from congruent Sr0.61Ba0.39Nb2O6 ceramics by the laser heated pedestal method. For these crystals, the phase components are detected by X-ray diffraction (XRD) analysis and dielectric properties are measured and compared. No other solid solutions during crystal growth are detected by XRD analysis. Two relaxations are observed by dielectric spectroscopy in a distinct temperature range and the relaxation mechanisms are investigated to explain the difference in dielectric behavior. The poling effect on the relaxation is also discussed.

Frequency dependent electrooptic property of SBN single crystal

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.

Random phase mask coded multiplexing for high-density and secure holographic memory

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.

Microwave electrooptic coefficient and modulation applications using ferroelectric single-crystal fibers

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.

Chirping effect on electrooptic modulator SBN single-crystal fiber in microwave cavity

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.