In-plane distribution of huge local permittivity of KTa1-xNbxO3 estimated from local phase transition temperatures and spatially averaged permittivity.

Potassium tantalate niobate (KTa1-xNbxO3, KTN) single crystals have a very large relative permittivity εr (>104) just above the paraelectric to ferroelectric phase transition temperature (TC). The quadratic electro-optic coefficient and the electro-strictive coefficient are also very large because of their proportionality to εr2. However, the local relative permittivity can easily vary spatially due to the incongruently melting nature of KTN.

Analyses of optical rays in KTN optical beam deflectors for device design.

The potassium tantalate niobate (KTN) optical beam deflector is an electro-optic deflector without any moving parts that works at frequencies higher than 200 kHz. In this paper, we discuss the performance parameters of this deflector. Optical beams are bent by the spatial distribution of the refractive index in the KTN crystal block used in this deflector.

Anomalous index modulations in electrooptic KTa(1-x)Nb(x)O(3) single crystals in relation to electrostrictive effect.

KTa(1-x)Nb(x)O(3) is known for its huge Kerr effect, which is a second order electrooptic (EO) effect. By utilizing the large refractive index change Δn of this EO effect, a fast optical beam deflector has been realized. However, anomalous spatial distributions of Δn were observed with this beam deflector.

Charge distributions in KTa₁₋xNbxO₃ optical beam deflectors formed by voltage application.

Controlling the space charge distributions in a crystal is indispensable for controlling a KTa₁₋xNbxO₃(KTN) optical beam deflector. The space charge is built up by applying a voltage and injecting electrons into the KTN crystal. Although a homogeneous distribution is preferable, we observed experimentally that the injected electrons concentrated in the vicinity of the cathode and for some samples the concentration was much lower around the anode.

Trapped charge density analysis of KTN crystal by beam path measurement.

Because the function of a single crystal of potassium tantalate niobate (KTa(1-x)Nb(x)O(3), KTN) is largely decided by the trapped charge density inside it, it is essential to determine its value. We quantitatively estimate the charge density using two optical analysis methods, namely by investigating KTN's deflection angle when it is used as a deflector and by investigating KTN's focal length when it is used as a graded-index (GRIN) lens. A strobe technique is introduced with which to perform the measurement.

Polarization independent varifocal lens using KTN crystals.

We fabricated a polarization-independent varifocal lens using KTa(1-x)Nb(x)O3 (KTN) crystals. The polarization dependence of the KTN crystal is effectively compensated for by combining a pair of KTN lenses and a half-wave plate. This compensation is achieved by a total electro-optic effect, which consists of the Kerr effect and the elasto-optic effects via the electrostrictive and elastic strains in the KTN crystal.

Fast response varifocal lenses using KTa(1-x)Nb(x)O3 crystals and a simulation method with electrostrictive calculations.

We fabricated cylindrical varifocal lenses with fast responses by using the strong Kerr effect of KTa(1-x)Nb(x)O(3) (KTN) single crystals. We observed focus shifts of up to 87 mm with the assistance of a 250 mm focal length lens, which corresponds to a focus shift from infinity to 720 mm by the KTN lens itself. The response time was as fast as 1 μs.

Orthogonal aperture multiplexing for multilayered waveguide holographic read-only memories.

A multilayered waveguide holographic read-only memory is a promising candidate for the next generation of optical data storage systems. We improved the data density of the memory by using a multiplexing method with a set of orthogonal optical masks. We multiplexed as many as nine images into one waveguide hologram, and all the observed images had negligible cross talk.