Silica Crystalline Colloidal Array Deep Ultraviolet Narrow-Band Diffraction Devices

We developed a facile method to fabricate deep ultraviolet (UV) photonic crystal crystalline colloidal array (CCA) Bragg diffraction devices. The CCAs were prepared through the self-assembly of small, monodisperse, highly surface charged silica particles (∼50 nm diameter) that were synthesized by using a modified Stober process. The particle surfaces were charged by functionalizing them with the strong acid, non-UV absorbing silane coupling agent 3-(trihydroxylsilyl)-1-propane-sulfonic acid (THOPS). These highly charged, monodisperse silica particles self assemble into a face-centered cubic CCA that efficiently Bragg diffracts light in the deep UV. The diffracted wavelength was varied between 237 nm to 227 nm by tilting the CCA orientation relative to the incident beam between glancing angles from 90° to ∼66°. Theoretical calculations predict that the silica CCA diffraction will have a full width at half-maximum (FWHM) of 2 nm with a transmission of ∼10−11 at the band center. We demonstrate the utility of this silica CCA filter to reject the Rayleigh scattering in 229 nm deep UV Raman measurements of highly scattering Teflon.