Controlling and concentrating infrared radiation has the potential to significantly impact infrared sensors, thermal imaging devices, as well as heat conversion systems. As most molecules have vibrational modes in the infrared range, they reradiate a great portion of the incident radiation instead of efficiently transmitting it. As a promising alternative, plasmonic gratings not only offer low-loss transmission of infrared radiation, but also compress the long infrared wavelengths. This localization effect greatly improves the sensing resolution and offers high-intensity fields at scales much smaller than the infrared wavelengths in free space. Such high intensities are invaluable probes for revealing light- matter interaction in nanoscale dimensions previously inaccessible. The challenge of creating low-loss materials in the infrared has been a nano-engineering feat utilizing functional gradients to guide and localize radiation. Recent advancements in nanofabrication, as well as a deeper understanding of light-matter interaction, have led to the realization of these plasmonic light-trapping gratings. We show the applicability of these structures as sensors for 1- detecting infrared signatures of molecules, 2- imaging, including bio-imaging, 3- concentrating thermal infrared radiation for energy harvesting. Our proposed structures utilize a gradient in the strength of plasmonic coupling between surfaces in close proximity to each other. Using this technique it is possible to fabricate such surfaces which possess a uniform depth and can be mass-produced using nano-imprint techniques.
Project end date: 09/15/16