Realization of Optical Beam Steering for Integrated Lidars
In designing next-generation lidars, it is essential to propose a suitable method for realizing non-mechanical optical beam steering. Meanwhile, tunable metasurfaces have shown promising abilities in realizing this requirement. Here, the recent advances in the design of tunable metasurfaces have been reviewed, and two new metasurfaces for achieving optical beam steering in the operational wavelength of lidars (in the near-IR regime) have been proposed. The first design is a tunable metasurface based on phase change materials and transparent graphene heaters. The relation between the applied voltage and the reflected electromagnetic wave characteristics has been specified by performing comprehensive electromagnetic and Joule heating studies. The studies show that by applying a voltage difference in the 9.25-11.1 Volts range, the phase of the reflected wave can be tuned in 0° to -270° range. Finally, it was found that the proposed structure is able to steer the reflected beam in the ±65° range. The second proposed structure is a tunable metasurface capable of steering the reflected beam on two orthogonal axes. The tunability of the proposed metasurface is realized by embedding a thin layer transparent conducting oxide inside the structure. In this study, the relation between charge carrier densities and applied voltage has been specified by solving the drift-diffusion equations inside the transparent conducting oxide. Then, the relationship between the applied voltage and the electromagnetic response of the unit-cell has been calculated using the Drude model. The studies show that by applying a voltage difference in 0-8 volts range, the phase of the reflected wave can be tuned in the 0°-270° range. In the final step, the proposed structure’s capability as a beam steering device has been analyzed. The results of this part represent the ability of the structure in steering the reflected beam on two orthogonal axes.