The recently evolved field of Complex light is the study of custom light beams with tailored intensity, phase, polarization or even propagation trajectory. These beams are of interest due to their interesting properties. For example, beams like the Bessel and the Airy beam remain diffraction-free over long distances, in addition to this the Airy beams tend to freely accelerate during its propagation. On the other hand, Laguerre Gaussian beams have helical wavefronts that can carry both spin and orbital angular momenta. Due to these interesting features, these beams are making their way into cross-disciplinary applications such as high-speed optical communications, optical trapping, microscopy and quantum optics. Several approaches have been reported to generate these complex light fields. Most of these techniques suffer from low efficiencies as they are based on binary diffractive optical elements (DOE) and spatial light modulators (SLM)-the former suffers from diffraction losses and the latter are polarization sensitive. Very recently, the field of metasurfaces gained popularity due to their ability to offer spatially varying phase response and low intrinsic losses. These devices also offer high transmission efficiencies (over 85%) and are not sensitive to the incident polarization.
In this talk, we will discuss different methods to generate complex light fields such as a Binary DOE. As an example, I will present a technique to engineer the axial intensity (AI) of a Bessel beam so that it has a desired AI over long (>3 cm) Depth of Focus (DOF). Due to the low efficiency of binary DOE, Grayscale Electron Beam Lithography (GEBL) was also studied. I will discuss the fabrication process and experimental calibration results for Grayscale/multilevel DOEs and their advantages over Binary DOEs. Finally, some initial simulation work on the dielectric metasurfaces will be presented.
All are cordially invited.