Temperature modulated nanoplasmonics

The optical properties of metallic nano-structures are intimately related to their temperature variation, characteristics which can be exploited for applications such as photocatalysis [1], nanochemistry [2] or sensor devices [3]. Here we show how the geometrical characteristics of the nano-structure, which are related to the structure optical response [4, 5], can in fact be used to modulate the temperature response. The idea is that when metallic structures interact with an electromagnetic field they heat up due to Joule effect. The corresponding temperature increase modifies the optical response of the structure and thus its heating process. The key finding is that, depending on the structures geometry, absorption efficiency can either increase or decrease with temperature. Since absorption relates to the thermal energy dissipation and thus to temperature increase, the mechanism leads to positive or negative loops. Consequently, not only an error would be made by neglecting the role of temperature, but it would be not even possible to know, a priori, if the error is towards higher or lower absorption values. The model, which does not require any fitting parameter, can be utilized to study opto-thermal phenomena when high temperature or high intensity sources are employed.