Design and fabrication of dielectric nanostructured Luneburg lens in optical frequencies

A dielectric subwavelength Luneburg lens structure was designed using Hamiltonian ray tracing, and fabricated using electron beam lithography. Analysis from Hamiltonian ray tracing was in agreement with finite difference in time domain (FDTD) method with wavefront error between the two methods below λ/8, while an improvement in speed of approximately 100 times was observed. The fabricated Luneburg lens structure was tested with a fiber laser with a wavelength of λ=1.55μm, and proved its capabilities of focusing.