Fabrication of Angstrom Wide Notch Filters Using Laser Induced Densification.

A unique method for producing very stable, sub-angstrom wide, reflection notch, and bandpass filters, with high optical rejection is proposed. This method takes advantage of a subtle process observed in vacuum ultra-violet (VUV) lithographic systems using fused silica optics known as, laser induced compaction. Multiple exposures of high power excimer radiation induces very small index of refraction changes in VUV grade fused silica. We propose using laser induced compaction-to produce sub-angstrom wide laser reflection and bandpass holographic filters. The advantages of high stability, and low cost, of these fused silica holographic filters will open up a wide range of applications in such fields as Raman spectroscopy, laser communications, and improved spectral resolution of laser sources. Since these holograms are imprinted into bulk fused silica, they can be ground and polished into lenses and optical elements. Fused silica holography builds on existing volume hologram techniques and laser densification is currently an active area of materials research. For these reasons, this technique provides the opportunity for high return on a unique innovation of present technology. In Phase 1, we will design a holographic optical bench, conduct material studies to better understand laser densification, and conduct proof of concept experiments. In Phase 2 we will construct the full-up holography bench, fabricate components and characterize the process. Applications for angstrom wide, high optical density notch and band pass filters include: Raman spectroscopy, separation of very close laser modes, high spectral resolution of laser sources, and improved signal to noise detection in laser based communications and laser based chemistry.