For the last five years, the majority of work in my group has studied metamaterials at mid-wave infrared and long-wave infrared wavelengths. This range, which corresponds to thermal radiation, is interesting both in terms of fundamental science and for various applications.
On the application side, some of our first work was on thermal regulation — designing materials that adjust their thermal radiation automatically, in order to keep their temperature fixed. This property is likely to prove useful for energy-efficient temperature control on satellites and perhaps even in buildings. We have also considered how thermal emitters could be used as sources for communication. Could information potentially be encoded in the emission patterns, in such a way that a message could be sent securely? We have published a series of papers exploring the algorithms for encryption as well as the implementation in experiment.
On the more fundamental side, we have looked at the basic, scientific properties of thermal radiation. For example, we have looked at how to focus the thermal radiation from an object to a confined spot, as well as how to tailor its spectral and angular characteristics. We have even examined a fundamental property known as Kirchhoff’s Law: the requirement that absorptivity and emissivity at any particular wavelength and angle are equal. We have investigated strategies for breaking this equality that result from carefully modulating the properties of the metamaterial in space and time. Meanwhile, we have worked with our collaborators to realize experimental implementations of tunable metamaterials that could achieve the promise of our designs. While specific applications for these properties may as yet be unknown, this work illustrates the rich scientific potential for tailoring the characteristics of thermally emitted radiation using metamaterials.
Alongside our work on infrared emitters, we have been hard at work building infrared detectors. In several recent papers, we have demonstrated the potential of black phosphorus for infrared detection. In this effort, we have incorporated all of the tips and tricks that we have learned from the study of infrared metamaterials to implement detectors that can efficiently absorb light as well as provide tailored spectral response.
What’s next? This will be the subject of my next post.
