  A new approach to perform analog optical differentiation is presented using
half-wavelength slabs. First, a half-wavelength dielectric slab is used to
design a first order differentiator. The latter works properly for both major
polarizations, in contrast to designs based on Brewster effect [Opt. Lett. 41,
3467 (2016)]. Inspired by the proposed dielectric differentiator, and by
exploiting the unique features of graphene, we further design and demonstrate a
reconfigurable and highly miniaturized differentiator using a half-wavelength
plasmonic graphene film. To the best of our knowledge, our proposed
graphene-based differentiator is even smaller than the most compact
differentiator presented so far [Opt. Lett. 40, 5239 (2015)].
