M. R. Shenoy

Grating-assisted non-linear directional coupler based optical switch with reduced critical power

Abstract We present a novel design of an optical switch based on grating-assisted non-linear directional coupler (GANDC) which consists of two non-identical waveguides, with a periodic refractive index perturbation in between the waveguides, along the direction of propagation. The proposed design of the optical switch reduces the critical power by a factor ~25, as compared to the conventional non-linear directional coupler-based switch, with potential applications in photonics.

Electro-optic switching in liquid crystal core waveguide at 1550 nm wavelength

We report fabrication and characterization of a liquid crystal core waveguide (LCW) at 1550 nm wavelength. The fabricated LCW consists of a guiding nematic liquid crystal layer of 5CB, surrounded by thin cladding layers of the polymer AZ15nXT, which are sandwiched between two ITO-coated glass plates. The threshold voltage and extinction ratio of the LCW are measured to be ≈ 4.0 V and > 6 dB, respectively, for optical switching application at the wavelength of 1550 nm. With an applied square-wave voltage at 2 Hz, the rise and fall times of the LCW have been measured as 23 ms and 38 ms, respectively, at room temperature. The experimental result shows that such electrically-controlled LCWs could have potential application for routing in optical communication and photonics.

Design and characteristics of a highly sensitive refractive index sensor based on a grating-assisted strip waveguide directional coupler

We present the design and simulated characteristics of a highly sensitive refractive index sensor based on two coupled asymmetric strip waveguides with a top-loaded grating structure on one of the waveguides. The proposed sensor would be a on-chip device with a high sensitivity of ∼ 1.5 × 104 nm/RIU.

Analysis of a Novel Grating-Assisted Directional Coupler by Using the Normal Mode and Coupled Mode Analyses

We present a novel structure of the directional coupler which consists of two non-identical waveguides, with a periodic refractive index perturbation along the direction of propagation. We have compared the coupling characteristics obtained by using the approximate coupled mode analysis and the exact normal mode analysis for the grating-assisted directional coupler. We find that, for the proposed structure, using the modes of the isolated waveguides in the coupled mode theory does not give accurate results, and one should apply the normal mode analysis to obtain the coupling characteristics.

Electrically-Controlled Periodic Segmented Waveguide With a Nematic Liquid Crystal Core

We report the first fabrication of electrically-controlled periodic segmented waveguides, of duty cycles 0.33 and 0.5, with a nematic liquid crystal core region, surrounded by AZ15nXT (negative photoresist) cladding, on ITO-coated glass substrates.

Realization of an Electrically-Controlled Optical Switch Using Nematic Liquid Crystal Core Waveguide

We report fabrication and characterization of a nematic liquid crystal waveguide on an ITO coated glass substrate, which behaves as an electrically-controlled optical switch with a small threshold voltage of 1 V.