This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Centini, M.Sibilia, C.D’Aguanno, G.Bertolotti, M.Scalora, M.Bloemer, M. J.Bowden, C. M.2020-05-292020-05-292000-10-06M.Centini et al., Reflectivity control via second-order interaction process in one-dimensional photonic band-gap structures, Optics Communications Volume 184, Issues 1–4 (2000), Pages 283-288, https://doi.org/10.1016/S0030-4018(00)00927-5https://doi.org/10.1016/S0030-4018(00)00927-5http://hdl.handle.net/11603/18791We exploit the nonlinear reflectivity of a pulse at the fundamental frequency induced by a second harmonic signal in one-dimensional photonic band gap structures for applications to fast control of light-by-light and all optical signal processing. We find that the enhancement of nonlinear gain near the band edge, coupled with a suitable choice of the relative phases between the input pulses, leads to significant reflectivity and transmittivity changes of the input pump pulse for structures only a few microns in length.6 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Public Domain Mark 1.0http://creativecommons.org/publicdomain/mark/1.0/Text