Raman Imaging Gallery - Raman Imaging of Holographic Gratings Inscribed on Polymer Thin Films
LPCM, UMR 5803 CNRS,
Université Bordeaux 1,
351, Cours de la Libration,
33405 Talence cedex,
France
Tel: +33 (0)5 40 00 29 01
Fax: +33 (0)5 40 00 84 02
Email: f.lagugne@lpcm.u-bordeaux1.fr
Figure 1
Raman image (Figure 1) from a thin film of azobenzene - containing polymer thin film (300 nm) that is periodically structured (periodicity of ~1 m). Raman measurements were recorded with a LabRAM HR 800 (HORIBA Jobin Yvon) spectrometer combined with an inverted microscope (Olympus IX 71) and a X,Y Piezoelectric stage to position the sample with the best accuracy and repeatability. A 100X, 0.9 NA microscope objective was used. A Raman spectrum (Fig. 2) was recorded every 100 nm along the X and Y directions with an integration time of 5 seconds per spectrum ( excitation=752.4 nm). The variation of the Raman signal was integrated over the [1060-1180]cm-1 spectral domain (Figure 3). It must be pointed out that details on the Raman profile are obtained with a spatial resolution better than λ/2 (at the diffraction limit).
Figure 2: Raman Spectra of azobenzene polymer. Acquisition time 5 sec.
Figure 3: Variation of the Raman intensity over the X and Y directions.
About the inscription of the two-dimensional grating.
Using holographic techniques we have structured the surface in a one step procedure (no wet nor photocuring processing) along the X and Y directions. A grating is first inscribed with grooves along the X direction, the sample is rotated by 90° and a second grating is inscribed with grooves along the Y direction. The intensity of the 1st diffracted orders is monitored to have equal intensities in both X and Y directions. The atomic force microscopy (AFM) images shown in Fig.3 exhibit a periodic structure on large surfaces with a height amplitude varying from 50 to 110 nm.
Figure 4: AFM images in 3D and 2D representations and profile of the height variations.
References
"Chromophore Orientations upon irradiation in gratings inscribed on azo dye polymer films: a combined AFM and confocal Raman microscopic study", F.Lagugné-Labarthet, J.L.Bruneel, T.Buffeteau, C.Sourisseau, J.Phys.Chem B, 2004, 108, 6949.
"Molecular orientations in a nonlinear optical azopolymer diffraction grating: odd and even order parameters from near-field second harmonic generation and far-field Raman microscopies", F.Lagugné-Labarthet, C.Sourisseau, R.D.Schaller, R.Saykally, P.Rochon, J. Phys. Chem B, 2004, 108, 17059.
