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Inducing Unconventional Optical Behavior in Materials Using Confined Light
Prashant Jain
Beckman Fellow 2016-17

This research focuses on a study of how photons behave when confined to the nanoscale and what unique optical phenomena we can elicit from such confinement. The proposed studies are designed to explore how one can use photon confinement to fundamentally alter the optical response of light absorbers and thereby control the flow of energy in these materials, such that these energy conversion processes have an enhanced utility in solar energy harvesting.

Professor Jain will leverage optical resonances of metal nanoparticles to generate such confined photons. The optical excitation of resonances in metal nanostructures results in the generation of intense electric fields around the nanostructure. There is immense untapped potential for employing these intense fields for fundamentally altering light-matter interactions in materials and thereby achieving much more directed and efficient flow of energy. Professor Jain will focus on two examples:

a) Titania is a semiconducting material that absorbs ultraviolet light, but has little absorption of visible sunlight. Here, a scheme to induce non-natural visible light absorption in titania by placing this material within a strongly focused near-field of a carefully designed metal nanostructure will be pursued. In addition to being fundamentally interesting, visible-absorption induced in this manner can open up the technological potential of harvesting sunlight for generating hydrogen from water using a titania photocatalyst.

b) Typically, light-absorbers, following photoexcitation, lose their excitation energy to thermal dissipation or heat. This is because thermal dissipation—vibrational cooling—is much faster than the process of conversion of the excited state into an emissive photon or a voltage-generating exciton. By placing such absorbers in a strong near-field, the latter processes, which are much more productive for energy generation, can be made much faster. Thereby, thermal dissipation, which is an undesirable energy loss mechanism and a fact of nature, can be beaten at its game.