  We present a theoretical study of radiative heat transfer between dielectric
nanogratings in the scattering approach. As a comparision with these exact
results, we also evaluate the domain of validity of Derjaguin's Proximity
Approximation (PA). We consider a system of two corrugated silica plates with
various grating geometries, separation distances, and lateral displacement of
the plates with respect to one another. Numerical computations show that while
the PA is a good approximation for aligned gratings, it cannot be used when the
gratings are laterally displaced. We illustrate this by a thermal modulator
device for nanosystems based on such a displacement.
