Abstract

One of the major challenges for emerging planar subwavelength micro lens is the significant chromatic behavior due to phase mismatch of subwavelength phase shifters. In this work, the achromatic micro grating lens covering the whole visible wavelength is demonstrated by utilizing relatively low index contrast gratings. Based on the unique chromatic phase shift behavior of polymer nano structure, we have designed and fabricated a broadband subwavelength achromatic micro lens that can cover 250 nm of visible bandwidths (from 435 nm to 685 nm) with focal shift less than 5%. Our works also represent the first time to design, fabricate and characterize micro grating lens (7 microns in size) promising for compact integrated nanophotonic devices on chip. In addition, there are more advanta ges of using a polymer based micro lens such as easy fabrication on flexible substrate and potential applications including imaging, spectroscopy, lithography, laser fabrication and future integrated wearable devices.

© 2018 The Author(s)