Main_manuscript_JCP_template

Sample title 5
FIG. 8. Scheme of the experimental setup. λ/2: half-wave plate,
SLM: phase-only spatial light modulator, M: mirror, L: lens, P: pinhole,
S: sample, MO: infinity-corrected microscope objective and
Cam: camera.
tance between the stripes varies between 25.6 µm (Fig. 9a),
31.4 µm (Fig. 9b) and 37.2 µm (Fig. 9c). For all of them,
the polarization of the light is perpendicular to the stripes and
the illumination time is 20 h. The intensity varies slightly between
158 mWcm −2 (Fig. 9a), 164 mWcm −2 (Fig. 9b) and
151 mWcm −2 (Fig. 9c).
The line profiles extracted from the topography images can
provide insight into the roughness of the surface, which can be
directly correlated to the polymer motion. Line profiles for the
sample in Fig. 9a show a valley of approximately 12 µm wide
and a plateau which is 26 µm wide. The average depth/height
of these features is between 60 nm and 100 nm. The line profiles
of the other two samples show valleys of the same width,
while the width of the plateaus varies. Thus, comparing the
dimensions of the topographical features in these images to
the respective illumination patterns, we can conclude that the
azopolymer has the tendency to move away from the bright
regions in the illumination pattern and accumulate in the dark
regions.
Moreover, the influence of the polarization on the SRG formation
is investigated. While in Fig. 9 the polarization is perpendicular
to the stripes, in Fig. 10 it is parallel. Otherwise
the illumination parameters are the same as in Fig. 9a with an
illumination time of 20 h and an intensity of 158 mWcm −2 .
Again the width of the valleys correspond to the width of the
bright stripes and the plateaus to the dark regions in between.
Also the depth of the structures is again in the range of 60 nm
to 100 nm as for the illumination with perpendicular polarization.
The only difference is the appearance of small bead-like
structures of 10 nm to 20 nm height in the valleys.
FIG. 9. Illumination patterns with different distances between the
bright stripes and the respective AFM topography images and line
profiles: (a) 25.6 µm, (b) 31.4 µm and (c) 37.2 µm. The line profiles
are extracted across the whole width of the respective scan image at
points indicated by the colored arrows. Laser light polarized perpendicular
to the striped pattern is used.
C. Merging theory and experiment
The simulation predicts that during illumination maxima
form in the exposed regions and then migrate from the sides
into the dark regions, as has been observed similarly earlier
by Yadavalli et al. 35 . Double-peak substructures similar to
those formed in our simulation after cooling have also been
FIG. 10. Illumination pattern with 12.8 µm wide bright stripes with
25.6 µm in between and respective AFM topography images and corresponding
line profiles of the illuminated azopolymer sample. The
line profiles are extracted across the whole width of the scan image at
points indicated by the colored arrows. The polarization of the laser
beam is parallel to the illumination pattern.