Biomedical Engineering Reference
In-Depth Information
Fig. 8.35
(
a
)and(
b
) Cross-sectional TEM images of the nanostructures from back contour feather
barbs of
Sialia sialis
and
C. maynana
, respectively. (
c
)and(
d
) Small-angle X-ray scattering data
for feather barbs of
S. sialis
and
C. maynana
, respectively. Scale bars: (
a
)and(
b
) 500 nm; and (
c
)
and (
d
) 0.025 nm
1
of spatial frequency (Reproduced from [
145
])
Coherent light scattering is conceptually the correct understanding for the non-
iridescent structural coloration produced by amorphous photonic structures [
6
,
141
-
147
], but it is not the ultimate physical mechanism. Moreover, the simple translation
of Fourier power spectra into reflection spectra by using the Bragg-like condition
could be problematic since the Bragg condition is only valid for very weak scattering
or dilute scatters. This is because for amorphous photonic structures light scattering
is far from weak owing to the short-range order. On the other side, the translation
procedure relies solely on the structural information, i.e., the structure factor. As is
known, reflection is related not only to the structure factor but also to the detailed
spatial distribution of refractive index.
