System Integration


In this research area we investigate the integration of nanostructures on macroscale systems. The goal is to enhance the performance and functionalize such systems with unique properties of nanostructures. This multi-scale approach enables physical response for all incorporated lengthscales. Potential application includes integrated diffractive solar concentrators.

Antireflective In-Plane Solar Concentrator

In addition to the antireflection effects, photonic nanostructures can also be used to trap light. We are investigating the use of such nanostructures on a glass window to re-direct and concentrate ambient sunlight to the edge, where it can be captured by a solar cell (as shown above) [1]. This effectively functionalizes windows are solar harvesters, which can serve as a building energy source. The nanostructures can also selectively trap a certain color wavelength, enabling spectra splitting to bandgap-matching solar cells. We have demonstrated 2% energy conversion efficiency, which can be improved by optimizing for structure geometry. These structures can be applied to existing windows and can be one aspect of the progress towards zero-emission buildings.

Gradient-Index Antireflection Diffractive Optics

Similar to planar surfaces, diffractive optical elements also suffers from Fresnel losses which takes the form of reflected diffracted orders. Using the same bio-inspired principles, it is possible to design a nanostructured gradient-index (GRIN) medium where the reflected orders can be suppressed, transfering all energy into transmissed orders [2]. The above figure illustrates the simulated electric field magnitude of reflected orders for a diffraction grating without (left) and with (right) the optimized nanostructures (click on figures to show simulated movie).

Such a nanostructured GRIN element can be fabricated using a combined lithographic and self-assembly approach, as shown in the above figure. The micrographs depict a diffractive microstructure with engineered nanoscale surface texture. The Fresnel losses are over two orders of magnitude lower than a traditional element over broad wavelength band and large incident angles [3].


[1] J. Tippens, A. Bagal, X. A. Zhang, and C.-H. Chang, “Nanostructured antireflective in-plane solar harvester,” Optics Express, 26(16), A840-A850, 2017. [link] [2] C.-H. Chang, L. Waller, and G. Barbastathis, “Design and optimization of broadband wide-angle antireflection structures for binary diffractive optics,” Optics Letters, 35, 907-909  (2010). [link] [3] C.-H. Chang, J. A. Dominguez-Caballero, H. J. Choi, and G. Barbastathis, “Nanostructured gradient-index antireflection diffractive optics,”Optics Letters, 36, 2354-2356 (2011).  [link]