Photonic-chip based free space beam shaping and steering for advanced optical microscopy application

Photonic-chip-based light illumination has recently found applications in optical microscopy and nanoscopy methodologies. The photonic chip removes the dependency on imaging objective lenses to generate the required illumination patterns for different microscopy methods. Until now all the reported chip-based optical microscopy methods exploit the evanescent field present on top of a waveguide surface and are thus inherently limited to two dimensional microscopy. Here, we perform systematic simulation studies to investigate different chip-based waveguide designs for static and dynamic shaping of light beams in the free-space. The simulation studies have been carefully designed considering the photo-lithography limitations and wavelength spectrum (405 nm to 660 nm) that is of interest in fluorescence based optical microscopy and nanoscopy. We first report the generation of a quasi-Bessel beam (QBB) using an on-chip axicon made at the end facet of a planar waveguide to mimic light sheet illumination. This is extended to the implementation of a counter propagating QBB for lattice light-sheet applications. The double axicon, a derivative of the axicon generates superimposed Bessel beams (SBB). Its waveguide-based implementation is proposed and analyzed. Finally, we investigate an optical phased array (OPA) approach to allow dynamic steering of the output light in the free-space. The aim of this study is to find suitable waveguide design parameters for free-space beam shaping operating in the visible spectrum opening possibilities for three-dimensional chip-based optical microscopy.