Nanofabrication has enabled rapid development of state-of-the-art electronic and optical devices. With nanofabricated feature size going down to become comparable, or even smaller than, the visible wavelength, some unique optical properties, which are different from their macroscale behaviours, appear. Nanostructure engineering enables us to exploit these unique properties to achieve highly efficient, compact and cheap optical devices.
Quantum cascade lasers was one of the major optical accomplishment of the 20th century. With its wide tuning range and fast response time, QCLs have been adopted in diverse array of applications from environmental monitoring, health, safety, defense to medical diagnostics. Recently, a number of novel waveguides that utilize dielectric structures and metallic components have gained significant interest as they can simultaneously achieve low modal loss and tight confinement. In the first part, we demonstrate successful integration of microfabrication and variety of advanced nanoimprint lithography techniques to fabricate gold nanoholes on top of micro ridge for application in QCL. The periodic sub-wavelength air surface plasmon waveguide created has potential to improve long wavelength QCL by increasing confinement while maintaining low loss like dielectric waveguide.
In the second part, we further use NIL, as a low-cost technology with large-area nanopatterning capacity, to demonstrate a biosensor with high fluorescence enhancement. We fabricated six different nanostructures to study the topological effects of nanostructures on fluorescence enhancement and showed seven-fold higher enhancement just from the topology. Then the effect of topology enhancement was combined with plasmonic nanostructures to increase the overall fluorescence enhancement of the plasmonic biosensor by two fold.