an optical processing system providing a rapid optical response , the system including : a first optical material sensitive to an effective refractive index change under photon absorption ; a first optical pump for optically pumping the first optical material at a first frequency so as to cause the first optical material to undergo an effective refractive index change by means of photon absorption ; a second optical pump for optically pumping the first optical material at a second frequency so as to cause the first optical material to undergo a rapid second refractive index change by means of stimulated emission .