Laurent Oyhenart

Enabling patterning of polymer optical devices working at visible wavelength using thermal nano-imprint lithography

Thermal Ultraviolet NanoImprint Lithography is a fast and reliable process to manufacture large scale integrated polymer-based optical components from a soft stamp. This technology already provides polymer integrated components for optical communications operating in the infrared region. However, several fabrication issues must be addressed to enable reliable mass production of optical components working in the visible region, especially when patterning large devices with nanometric features. In this work, we report our fabrication results on grating coupler and optical microring resonators with SU-8 resist. The device is conceived for monomode visible wavelength operation dedicated to future optical sensing applications. For this purpose, sub-micron waveguides are needed. We reported two main defects on soft stamp fabrication: partial sidewall detachment and shifted or double embossing of the features. Nanoimprinting SU-8 waveguides was achieved with the operational devices of the soft stamp.

Tunable photonic crystals controlled by spin-crossover material in Terahertz range

We use a spin crossover material as active defect inserted into a periodic structure of alternating layers of glass and air. By inducing the spin transition of the defect, a single defect mode of this Bragg filter designed for the submillimeter wavelength can be tuned over 15 GHz. This shows prospective applications of spin crossover materials at terahertz frequencies.

Tunable photonic crystals using ferroelectric materials

For microwave applications, there is a great demand for frequency tunable devices. Most of the time, these devices are obtained by including discrete components in the structures. We propose here to use a ferroelectric material with weak losses. It will be associated with frequency selective surfaces and photonic crystals. The application of an electric field to this structure, allows obtaining a tunable transmission.

Localized defects and random variations in 3D-PBG

The object of our study is to use photonic band gap structures (PBG) in the conception of materials with specific electromagnetic properties in microwave frequency range: absorbing, scattering or transparent materials. The main domains of applications are Electromagnetic Compatibility or uperstrates of antennas.

Analytical modeling of defects in 3D-PBG

The modeling of defects in PBG by traditional numerical methods is difficult because it requires much memory and computing time. An analytical method of multiple-scattering solves this typical problem for spherical inclusions. This method shows that weak random variations of the radius and position of the spheres do not generate notable modifications of the electromagnetic characteristics of the PBG.