article posted 19 May 2016
Professor Kathleen Richardson
The role of nano-scale heterogeneity fluctuations on the properties of optical composites
Prof. Kathleen Richardson
College of Optics and Photonics, University of Central Florida, Orlando FL USA
Next generation electro-optical /infrared (EO/IR) optical components and sensors require novel optical materials that serve specified optical functions and possess attributes which
can be tailored to accommodate specific optical design, manufacturing or component/device integration constraints. This includes the ability to engineer not only optical properties and
function, but also thermal and mechanical properties key to meeting fabrication and environmental demands. Over the past decade efforts by the UCF team and our collaborators have focused
on developing a toolbox of glass material chemistry options, processing methodologies and metrology tools that employ multi-component mid-infrared (MIR) transparent glasses (chalcogenide
glass (ChG) and heavy metal oxide (HMO) glasses) with tailorable physical properties for diverse applications.
This presentation reviews application-specific needs that can be realized in mid- and longwave infrared optical material systems when efforts to engineer base glass morphology and subsequent
microstructure to form optical nanocomposites, is successful. As has been well-documented in the non-oxide glass literature, chalcogenide glasses often have nano-scale phase separation as
an intermediate step which with suitable optical quality and loss levels, can be transferable to commercially relevant platforms. To realize this latter criteria, materials must be scalable
beyond the experimental sizes routinely realized in lab-scale experiments. Discussed are details as to how this morphology can impact the optical performance of glasses with tailored
refractive indices. We extend this discussion by reviewing recent efforts whereby these glasses can be converted to optical glass ceramic nanocomposites, enabling the creation of novel,
three dimensional (3D) gradient refractive index (GRIN) materials.
Gradient-index (GRIN) coatings and bulk lenses can provide significant performance enhancement and/or reduction in size, weight, and power (SWaP) in optical systems. The effective
refractive index, neff of the GRIN components can be engineered to create a spatially defined desired refractive index profile allowing optimization of the optical performance over
conventional homogeneous infrared (IR) materials. Anti-reflective (AR) GRIN coatings have been designed and fabricated which show significant performance enhancement over current state
of practice wide field of views (W-FOV) AR coatings. Bulk and thin film GRIN materials with broadband optical transmission have also been developed and show promise in providing
opportunities to reduce SWaP in complex and compact systems.