We present an optimization study of surface relief grating based sensors for use in optical remote point sensing. Our study includes the effects of geometrical characteristics of the photonic structure on the efficiencies of the first and second diffraction orders and the exhibited sensor responsivities of these orders. Our predictions are verified experimentally with measurements of surface relief gratings patterned by direct laser ablation on SiO 2 sol–gel nanocomposite material with embedded NiCl 2 nanocrystals developed for ammonia sensing.