Nanoengineering of a Negative-Index Binary-Staircase Lens for the Optics Regime
B. D. F. Casse, R. K. Banyal, W. T. Lu, Y. J. Huang, S. Selvarasah, M. Dokmeci, and S. Sridhar
Applied Physics Letters, V.92, P.243122 (2008)
We show that a binary-staircase optical element can be engineered to exhibit an effective negative index of refraction, thereby expanding the range of optical properties theoretically available for future optoelectronic devices. The mechanism for achieving a negative-index lens is based on exploiting the periodicity of the surface corrugation. By designing and nanofabricating a planoconcave binary-staircase lens in the InP/InGaAsP platform, we have experimentally demonstrated at 1.55 micrometers that such negative-index concave lenses can focus plane waves. The beam propagation in the lens was studied experimentally and was in excellent agreement with the three-dimensional finite-difference time-domain numerical simulations.