Guided-wave electro-optic characterization of BaTiO3 thin films using the prism coupling technique.

Ferroelectric BaTiO3 (BTO) thin films are grown by RF sputtering onto an indium tin oxide bottom electrode on a MgO single-crystal substrate. We have studied here the optical properties by the prism coupling technique. We report the ordinary and extraordinary refractive indices of the films, the film thickness, and the optical losses that are obtained on the planar waveguides: n0=2.224±0.001 and n(e)=2.219±0.001 at 1539 nm. Furthermore, in order to demonstrate the active property of the BTO films, we have investigated the electro-optic (EO) properties by using the change of the resonant coupling angle (variation of fundamental TE0 guided mode) when the transverse electric field is applied. The latter is induced by the refractive index variation (Δn) caused by the EO effect when a static electric field is applied transversely to the film. The EO coefficient obtain is about 18 pm/V for TE mode and 23 pm/V for TM modes at 1539 nm. This value illustrates the suitability of the BTO material thin film with a polycrystalline structure for applications such as modulations, switching, and interconnections.

Gallium-nitride-based plasmonic multilayer operating at 1.55 µm.

In this Letter, we have designed and fabricated a III-V semiconductor multilayer based on surface plasmon resonance (SPR) operating at the telecom wavelength. Optimization of the optogeometrical parameters and the metal/semiconductor layers required for this novel structure was conducted accurately by theoretical tools using the Maxwell equations. Technological fabrication of the device and its experimental characterizations using an evanescent coupling configuration was performed: the results have confirmed the existence of SPR associated to a sharp width response. This study could be a first step in the design of new plasmonic-semiconductor-based optical devices such as modulators and switches.

Effect of varying pore size of AAO films on refractive index and birefringence measured by prism coupling technique.

Anodic aluminum oxide (AAO) films with different pore sizes were prepared to modulate the effective refractive index and birefringence. To investigate the relationship between the refractive index and the pore size of the AAO film, optical constants were obtained using a prism coupler with various lasers. With experimental results, the dispersion curve of alumina itself without pores was extracted using a theoretical anisotropic model. We demonstrated that AAO films could offer a wide range of refractive index and birefringence values for optical device applications. Furthermore, index profiles as a function of the thickness of the AAO films were obtained by inverse Wentzel-Kramer-Brillouin approximation to examine the optical homogeneity.

Design, optimization and fabrication of an optical mode filter for integrated optics.

We present the design, optimization, fabrication and characterization of an optical mode filter, which attenuates the snaking behavior of light caused by a lateral misalignment of the input optical fiber relative to an optical circuit. The mode filter is realized as a bottleneck section inserted in an optical waveguide in front of a branching element. It is designed with Bézier curves. Its effect, which depends on the optical state of polarization, is experimentally demonstrated by investigating the equilibrium of an optical splitter, which is greatly improved however only in TM mode. The measured optical losses induced by the filter are 0.28 dB.

Photonic devices based on preferential etching.

We introduce a design concept of optical waveguides characterized by a practical and reproducible process based on preferential etching of crystalline silicon substrates. Low-loss waveguides, spot-size converters, and power dividers have been obtained with polymers. We have also aligned liquid crystals in the waveguides and demonstrated guided propagation. Therefore this technology is a suitable platform for soft-matter photonics and heterogeneous integration.