Diffractive optical elements with porous silicon layers.

We investigate the basic chromatic properties of dispersive surface relief diffractive optical elements with porous silicon (PSi) layers. Rigorous and scalar wavelength-dependent diffraction efficiencies are juxtaposed and compared to reflection coefficients of uniform silicon and PSi layers. The application of the device as an enhanced sensor is discussed. A spectral covariance criterion for efficient evaluation of the spectral changes induced by analyte filling the pores is presented. Experimental results for the device reveal an increased spectral selectivity of the diffractively structured PSi layers compared to uniform PSi layers.