  In this paper, we propose a method for tailoring the absorption in a photonic
crystal membrane. For that purpose, we first applied Time Domain Coupled Mode
Theory to such a subwavelength membrane and demonstrated that 100% resonant
absorption can be reached even for a symmetric membrane, if degenerate modes
are involved. Design rules were then derived from this model in order to tune
the absorption. Subsequently, Finite Difference Time Domain simulations were
used as a proof of concept and carried out on a low absorbing material
(extinction coefficient=10-2) with a high refractive index corresponding to the
optical indices of amorphous silicon at around 720 nm. In doing so, 85%
resonant absorption was obtained, which is significantly higher than the
commonly reported 50% maximum value. Those results were finally analyzed and
confronted to theory so as to extend our method to other materials,
configurations and applications.
