Investigation of Multi-Axis Beam Steering using Diffraction Grating
Optical beam-steering is becoming a key optical functionality in free space optical links used for communication and sensing. For example, in recent times, compact, wide-angle, fast, multi-axis beam steering is used extensively for LiDAR system in automotive vehicles, remote sensing platforms and deep-space optical communication. The state-of-the-art beam steering optics are typically based on mechanical, optical and/or electronic array designs. The present work investigates alternate schemes to perform multi-axis beam steering using one-dimensional diffraction gratings. Various schemes to perform multi-axis steering utilizing spectral scanning, pitch tuning and grating azimuthal rotation are discussed. More specifically, rigid silicon nitride gratings on glass substrate are designed for polarization-independent, spectrally scanned steering. The silicon nitride structures are optimized to achieve high diffraction efficiency for both linear polarizations by interfacing MATLAB based Genetic Algorithm Optimization and Lumerical FDTD based optical simulations. The dynamic steering is studied by varying the wavelength of incidence beam and azimuthal rotation of the grating about the normal to the grating. In diffraction gratings, the change in wavelength has the same effect as the change in pitch of the grating. Thereby flexible silicone material, Polydimethylsiloxane (PDMS) based grating is designed and optimized for polarization insensitive, high diffraction efficiency into a particular order and simulated for pitch tuning and azimuthal rotation. Lastly, experimental study of multi-axis beam steering using glass blazed gratings by incorporating spectral scanning and azimuthal rotation is discussed.