Jerome Wenger NanoBioPhotonics

Published recently in Optics Express, it’s freely available at :
http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-3-2276

A single nanometric aperture surrounded by a circular channel groove in a metallic screen can increase the electric field intensity inside the central aperture up to 50 fold. Detailed analysis of cavity modes and their coupling through surface plasmon wave determine the parameters leading to maximum field enhancement. This effect can be used in high-efficiency single-molecule fluorescence analysis in attoliter volumes.

Now it’s made available online : D. Gerard et al, Phys Rev B 77, 045413 (2008)

Briefly, we experimentally compare the properties of circular nanoapertures milled in gold and aluminium to enhance the fluorescence of dyes diffusing within the nanoapertures. Our main result is that nanoapertures in gold exhibit much higher fluorescence enhancement. We discuss the influence of a noble metal holding plasmonic resonances in the visible range such as gold. Altogether, these results provide crucial knowledge for the design of nanoapertures towards high-efficiency single-molecule analysis.

As an interdisciplinary project for students of the Ecole Centrale Marseille, a joint team with my lab developed a demonstration version of a trinocular microscope. The aim is to introduce students to the principles of image formation, Fourier optics, and basic contrast filtering techniques in microscopy.  This work follows a pioneering demonstration by Peter Evenett (Leeds, UK).

Two USB video cameras are used: the first one observes the image of the sample, the second is conjugated to the microscope objective’s back focal plane (Fourier plane). This allows a simultaneous monitoring of both direct and Fourier images.

As an example, the following picture shows the direct (left) and Fourier (right) images of gratings with two different pitches. Smaller pitches yield farer diffracted orders in Fourier space.

Different kind of filters can be set into the Fourier plane, direct observation on their influence on image formation can be inferred. In the following, a black mask is set in the back focal plane to suppress the central (non-diffracted) order. Only the first (plus and minus) diffracted orders are transmitted and contribute to the final image, giving a crisper contrast.

World’s first published studies on optical diffraction dating back to 1664, where the word “diffraction” itself was introduced for the first time. The original text is downloadable for free at the French National Library website http://gallica.bnf.fr/

Best wishes