Controlling the sign of chromatic dispersion in diffractive optics with dielectric metasurfaces
Diffraction gratings disperse light in a rainbow of colors with the opposite order than refractive prisms, a phenomenon known as negative dispersion. While refractive dispersion can be controlled via material refractive index, diffractive dispersion is fundamentally an interference effect dictated by geometry. Here we show that this fundamental property can be altered using dielectric metasurfaces, and we experimentally demonstrate diffractive gratings and focusing mirrors with positive, zero, and hyper-negative dispersion. These optical elements are implemented using a reflective metasurface composed of dielectric nano-posts that provide simultaneous control over phase and its wavelength derivative. In addition, as a first practical application, we demonstrate a focusing mirror that exhibits a five-fold reduction in chromatic dispersion, and thus an almost three-times increase in operation bandwidth compared with a regular diffractive element. This concept challenges the generally accepted dispersive properties of diffractive optical devices and extends their applications and functionalities.
© 2017 Optical Society of America. Received 22 February 2017; revised 3 May 2017; accepted 5 May 2017 (Doc. ID 287279); published 7 June 2017. Funding: Samsung Electronics; National Science Foundation (NSF) (1512266); U.S. Department of Energy (DOE) (DESC0001293); Defense Advanced Research Projects Agency (DARPA). E. A., A. A., and A. F. conceived the experiment. E. A., S. M. K., and Y. H. fabricated the samples. E. A., S. M. K., A. A., and Y. H. performed the simulations and measurements and analyzed the data. E. A., A. F., and A. A. co-wrote the paper. All authors discussed the results and commented on the paper. E. A. and A. A. were also supported by NSF. A. A. and Y. H. were also supported by DARPA, and S. M. K. was supported as part of the DOE "Light-Material Interactions in Energy Conversion," Energy Frontier Research Center. The device nanofabrication was performed at the Kavli Nanoscience Institute at Caltech.
Submitted - 1701.07178.pdf
Published - optica-4-6-625.pdf
Supplemental Material - optica46625s001.PDF