Renaud Bachelot (professor), Anne Laure Baudrion (assistant professor), Safi Jradi (assistant professor)
The purpose of the research group is to study the optical interaction between evanescent nanosources and photosensitive molecular systems. In particular, we focus our efforts onto nanosources associated to local enhanced fields of surface plasmon-polarition in metal nanoparticules (MNP). Our motivation is threefold:
This last point is in the challenging context of nanolithography and high density storage.
Regarding point 1): new optical properties of MNP are investigated by numerous techniques (SNOM, far-field spectroscopy, photon-emission electron microscopy…). These properties concern photoluminescence involving interband electronic transitions , second harmonic generation, near-field coupling, plasmonic modes in metallic nanocavity  and optical confinement above gold Nano wells .
Regarding points 2) et 3) : Two photosensitive molecular systems are investigated. They enable nanoscale photochemistry. The first system has been developed by the DPG for many years. It is a photopolymerizable liquid formulation sensitive to visible light. This system is very sensitive to oxygen and is characterized by an energy threshold above which no polymerization is possible. We take advantage of this feature to trigger polymerization in the enhanced optical near-field of MNPs while the far field (associated to lower energy density) does not lead to any polymerisation. This approach gives rise to granted national and regional projects*. It allows for controled fabrication of new Ag/polymer hybrid nanoparticles for nanophotonics (e.g. figure a). Moreover, by anisotropic nanoscale photopolymerization, we demonstrated a spectral degeneracy breaking in surface plasmon resonance in NPM . This first system is precisely characterized through the integration of submicrometer-sized polymer tips at the extremity of optical fibers .
The second system is made of azobenzene molecules grafted to a PMMA matrix. This material is self developing. It develops surface topography under optical illumination. This topography is related to the spatial distribution of the incident vectorial field. The involved molecular displacements result from cycles of izomerization of the azobenzene molecules. Optically induced surface topography can be modeled numerically by statistical Monte Carlo methods .
With this material, we carry out many studies, including
- near-field polarization sensitivity of optical molecular displacements [9,10],
- near-field nanophotolithography on film films [11,12],
- vectorial photochemichal near-field imaging of MNS [9,10] (example Fig. b),
- electromagnetic singularities at the extremity of metal tips. ,
- optical molecular nanomotors.
These studies open the door to new approaches of matter optical nanomanipulation.
* ANR 2007-2010 (projet ANR-blanc « photohybrid »), region Champagne Ardenne, UTT,..
(a) AFM image of a hybrid Ag/polymer nano-particule made by near-field surface-plasmon assisted photo polymérization. Bottom: optical intensity calculated in the vicinity of the original Ag particle illuminated by a linearly polarized monochromatic light. (b) Photochimical imaging (AFM image), based on molecular displacement of azobenzene-containing polymer in the near-field of an array of Ag particles (period = 1μm) illuminated by a circular light. Bottom: Intensity calculated in the vicinity of a Ag particule.
 Bouhelier, A., Bachelot, R., Lerondel, G.,Kostcheev, S., Royer, P., Wiederrecht, G.P. – “Surface plasmoncharacteristics of tunable photoluminescence in single gold nanorods” Physical Review Letters, 95, 267405/1-4. (2005). (2005).
 C. Hubert, L. Billot, P-M. Adam, R. Bachelot, P. Royer, J.Grand, D. Gindre, K. D. Dorkenoo, A. Fort, “Surface plasmon spectralcharacteristics of second harmonic generation in gold Nanorods”– Applied Physics Letters 90 pp 181105-181107 (2007).
 Bouhelier, A., Bachelot, R., Im, J.S., Wiederrecht, G.P.,Lerondel, G., Kostcheev, S., Royer, P. “Electromagnetic interactions inplasmonic nanoparticle arrays”, Journal of Physical Chemistry B, 109 (8), pp. 3195-3198. (2005).
 Douillard, L., Charra, F., Korczak, Z., Bachelot, R.,Kostcheev, S., Lérondel, G., Adam, P. M. and Royer, P., “Short rangeplasmon resonators probed by photoemission electron microscopy”. Nanoletters 8(3), 935-938 (2008).
 Jeffrey E. Hall, Gary P. Wiederrecht, Stephen K. Gray, Shih-HuiChang, Seokwoo Jeon, John A. Rogers, Renaud Bachelot and Pascal Royer,“Heterodyne apertureless near-field scanning optical microscopy onperiodic gold nanowells”– Optics Express 15 (7), pp 4098-4108 (2007).
 H. Ibn El Ahrach, R. Bachelot, A. Vial, G. Lérondel, J. Plainand P. Royer and O. Soppera, “Spectral degeneracy breaking in plasmonresonance of single metal nanoparticles by nanoscale near-fieldphotopolymerization” Physical Review Letters 98, (10),pp. 107402/1-4 (2007)
 Bachelot, R., Ecoffet, C., Deloeil, D., Royer, P., Lougnot,D.-J., “Integration of micrometer-sized polymer elements at the end ofoptical fibers by free-radical photopolymerization”, Applied Optics, 40 (32), pp. 5860-5871. (2001).
 M. Juan, J. Plain, R. Bachelot, P. Royer, G. P. Wiederrecht, S.K. Gray, “Statistical Model of photoinduced molecular motion inazobenzene-containing polymers“ ACS Spring meeting, New Orleans, 6-11April 2008.
 C. Hubert, R. Bachelot, J. Plain, S. Kostcheev, G. Lerondel, M.Juan, P. Royer, S. Zou, G. C. Schatz, G. P. Wiederrecht, and S. K.Gray. “Near-field polarization effects in molecular-motion-inducedphotochemical imaging”. Journal of Physical Chemistry C 112 ( 11 ), 4111 - 4116 (2008).
 Gilbert, Y., Bachelot, R., Royer, P., Bouhelier, A.,Wiederrecht, G.P., Novotny, L.“Longitudinal anisotropy of thephotoinduced molecular migration in azobenzene polymer films”, Optics Letters, 31 (5), pp. 613-615. (2006)
 Hubert, C., Rumyantseva, A., Lerondel, G., Grand, J.,Kostcheev, S., Billot, L., Vial, A., Bachelot, R., Royer, P., Chang,S.-H., Gray, S.K., Wiederrecht, G.P., Schatz, G.C. “Near-fieldphotochemical imaging of noble metal nanostructures”, Nano Letters, 5 (4), pp. 615-619. (2005).
 M. Derouard,J. Hazart, G. Lerondel, R. Bachelot, P. M. Adam,and P. Royer, “Polarization-sensitive plasmon interference printing ina photosensitive azo-dye polymer film”– Optics Express 15 (7) pp 4238-424 (2007).
 Bachelot, R., H'Dhili, F., Barchiesi, D., Lerondel, G., Fikri,R., Royer, P., Landraud, N., Peretti, J., Chaput, F., Lampel, G.,Boilot, J.-P., Lahlil, K. Apertureless near-field optical microscopy: Astudy of the local tip field enhancement using photosensitiveazobenzene-containing films. Journal of Applied Physics, 94 (3), pp. 2060-2072 (2003)