Jerome Wenger NanoBioPhotonics

Currenly open is a position for undergraduate internship training project working on nanophotonics for advanced fluorescence sensing and single molecule detection. More details are given here.

Relevant candidates have a physics, biophysics or engineering background, with a strong motivation and willingness to join a multidisciplinary international team.

The position can be continued as PhD project, conditionnal to the succesful application for a PhD grant.

According to national rules, undergraduate trainees will be supported by a monthly grant of 398,13 € (only valid or training periods longer than two months).

My team has recently published a study on second harmonic generation on single gold nanoapertures. This was released in the December 1st issue of Optics Letters. You can find a free reprint here.

Metal nanostructures are interesting emitters for second harmonic generation (SHG) radiation, which occurs essentially from the non-centrosymmetry breaking at the metal-medium interface for objects of the order of 50nm-100nm size.
At MOSAIC we demonstrate the ability of single-subwavelength-size nanoapertures fabricated in a gold metal thin film to enhance second-harmonic generation (SHG) as compared to a bare metal film. Nonlinear microscopy imaging with polarization resolution is used to quantify the SHG enhancement in circular and triangular nanoaperture shapes.

This study has two main results:
* The SHG enhancement on circular nanoapertures is demonstrated to originate from both phase retardation effects and field enhancements at the aperture edge.
* Triangular nanoapertures exhibit superior SHG enhancement compared with circular ones, as expected from their noncentrosymmetric shape.

Isotropic single-objective microscopy (ISO-microscopy) is a novel method developed by colleagues at the Fresnel Institute to overcome the limits set by diffraction in optical microscopy. With ISO-microscopy, light is focused into an isotropic spherical spot of about one wavelength dimension.

Watch this video to learn how ISO-microscopy works !

Two-photon excitation of single fluorescent molecules has generated much interest and expectations, especially for analytical sciences. However, current demonstrations struggle with low two-photon fluorescence rate per molecule and/or high background. In a recent publication in Biomedical Optics Express, we answer these challenges by using a single polystyrene microsphere under focused Gaussian illumination. This opens new opportunities to extend the applications of two-photon fluorescence detection.

1- We demonstrate a simple, robust, and low-cost solution to enhance the two-photon fluorescence signal per molecule up to one order of magnitude, without adding any significant photoluminescence noise. This goes significantly beyond the current state-of-the-art.

2- We perform a thorough characterization of the two-photon fluorescence enhancement in the vicinity of a single dielectric microsphere, and report 30x higher fluorescence enhancement factors than earlier work in the field.

3- The microspheres form an interesting structure to compare the gains in one- and two-photon excitation of fluorescence. Such comparison has been seldom reported in the litterature.