Nathalie Lorrain

Optical gain measurements in porous silicon planar waveguides codoped by erbium and ytterbium ions at 1.53μm

The on-off optical gain measurements as a function of the pump power were performed on porous silicon planar waveguides codoped by erbium and ytterbium ions. These measurements were obtained for different ratios of Yb concentration to Er concentration. The highest value of the gain was reached when the Yb concentration is three times higher than that of Er at a moderate 980nm pump power value equal to 70mW. Optical losses measurements have been performed on these waveguides and were equal to 2.1dB∕cm and an internal gain of about 6.4dB∕cm was obtained.

Integrated polymer micro-ring resonators for optical sensing applications

Micro-resonators (MR) have become a key element for integrated optical sensors due to their integration capability and their easy fabrication with low cost polymer materials. Nowadays, there is a growing need on MRs as highly sensitive and selective functions especially in the areas of food and health. The context of this work is to implement and study integrated micro-ring resonators devoted to sensing applications. They are fabricated by processing SU8 polymer as core layer and PMATRIFE polymer as lower cladding layer. The refractive index of the polymers and of the waveguide structure as a function of the wavelength is presented. Using these results, a theoretical study of the coupling between ring and straight waveguides has been undertaken in order to define the MR design. Sub-micronic gaps of 0.5 μm to 1 μm between the ring and the straight waveguides have been successfully achieved with UV (i-lines) photolithography. Different superstrates such as air, water, and aqueous solutions with glucose at d...

Guided Photoluminescence from Integrated Carbon-Nanotube-Based Optical Waveguides

Thin films and ridge waveguides based on large-diameter semiconducting single-wall carbon nanotubes (s-SWCNTs) dispersed in a polyfluorene derivative are fabricated and optically characterized. Ridge waveguides are designed with appropriate dimensions for single-mode propagation at 1550 nm. Using multimode ridge waveguides, guided s-SWCNT photoluminescence is demonstrated for the first time in the near-infrared telecommunications window.

Anti resonant reflecting optical waveguide structure based on oxidized porous silicon for label free bio sensing applications

In this letter we report on the use of an electrochemical process for the fabrication of anti resonant reflecting optical waveguide based on oxidized porous silicon. This method is known to allow the formation of various photonic structures (Bragg mirror, microcavity), thanks to the easy and in situ modulation of the porosity and thus of the refractive index. Planar anti resonant reflecting optical waveguide structure made from porous silicon is demonstrated to be very effective for low losses as compared to conventional resonant waveguide. Optical measurements carried out for TE and TM polarizations are reported and related to optical sensing.

Buried anti resonant reflecting optical waveguide based on porous silicon material for an integrated Mach Zehnder structure

A buried anti resonant reflecting optical waveguide for an integrated Mach Zehnder structure based on porous silicon material is achieved using a classical photolithography process. Three distinct porous silicon layers are then elaborated in a single step, by varying the porosity (thus the refractive index) and the thickness while respecting the anti-resonance conditions. Simulations and experimental results clearly show the antiresonant character of the buried waveguides. Significant variation of the reflectance and light propagation with different behavior depending on the polarization and the Mach Zehnder dimensions is obtained. Finally, we confirm the feasibility of this structure for sensing applications.

Theoretical investigation of Vernier effect based sensors with hybrid porous silicon-polymer optical waveguides

A new combination of porous silicon and polymer optical waveguides is investigated for two different designs of Vernier effect based sensors for the surface detection of Bovine Serum Albumin molecules (BSA). The hybrid structures studied consist of two cascaded micro-resonators for one and a micro-resonator cascaded with a Mach-Zehnder for the other. Because of its high specific surface and bio-compatibility, we use porous silicon to implement the waveguides in the sensing part of the sensor into which BSA molecules are grafted. Polymer waveguides are then used for the reference part of the sensor because of their low optical losses. We consider the opto-geometric parameters of both waveguides for single mode propagation. Finally, optimized designs, taking into account standard experimental wavelength shift measurement limitation are presented for both structures. We demonstrate a theoretical Limit Of Detection (LOD) of 0.019 pg.mm-2 and a sensitivity of 12.5 nm/(pg.mm-2) with these hybrid sensors. To our knowledge, these values are lower by a factor of 8 for the LOD and higher, by a factor of 200 for the sensitivity, as compared to state of the art Vernier effect biosensors.

High sensitivity optical biosensor based on polymer materials and using the Vernier effect

We demonstrate the fabrication of a Vernier effect SU8/PMATRIFE polymer optical biosensor with high homogeneous sensitivity using a standard photolithography process. The sensor is based on one micro-resonator embedded on each arm of a Mach-Zehnder interferometer. Measurements are based on the refractive index variation of the optical waveguide superstrate with different concentrations of glucose solutions. The sensitivity of the sensor has been measured as 17558 nm/RIU and the limit of detection has been estimated to 1.1.10-6 RIU.

Study of Optimized Coupling Based on Micro-lensed Fibers for Fibers and Photonic Integrated Circuits in the Framework of Telecommunications and Sensing Applications

We demonstrate the interest of expanded beam microlenses (around 55 µm of mode field diameter) to relax positioning tolerances and to decrease reflectance in single mode fiber to fiber interconnections . We also point out the interest of micro-lenses of very small mode field diameter (around 2 µm) to improve coupling efficiency in specialty fibers and integrated waveguides for non linear effects based functions and for sensors applications at a wavelength of 1.55 µm.

Integrated racetrack micro-resonator based on porous silicon ridge waveguides

Racetrack micro-resonator (MR), made from partially or totally oxidized porous silicon (PS) ridge waveguides fabricated with standard photolithography process, is reported. The design and the technological process are described including a study of waveguide dimensions that provide single mode propagation. Scanning electronic microscopy observations and optical characterizations clearly show that the MR based on PS ridge waveguides has been well implemented. As the MRs will be used for sensing application, we also present a preliminary theoretical study of the porous MRs sensitivity. A very promising theoretical sensitivity around 1200 nm/RIU (Refractive Index Unit) has been calculated for such porous racetrack MR.