Tunable multilayer‐film distributed‐Bragg‐reflector filter

The periodic multilayers of dielectric materials such as polystyrene/collodion or polystyrene/polyvinyl alcohol were fabricated by means of alternately dropping these solutions onto a spinner. As these materials are slightly elastic, a large shift of the center of the Bragg reflection by 650 A toward shorter wavelength is obtained by the compression of the multilayer. A periodic length Λ is controlled by adjusting both the rotation speed of the spinner and the concentration of the solutions.