Research Projects

Designing optical components that are ultracompact and can be easily reconfigured for various applications has been a primary goal for optical engineers, yet conventional approaches relying on mechanical elements add to the system's size and intricacy. Metasurfaces, however, allow precise wavefront control using subwavelength antenna arrays, eliminating the need for bulky curved optics. These structures reduce size, weight, power, and cost, enabling highly adaptable optical systems. One of the most significant practical applications of metasurfaces have been metalenses – ultracompact imaging systems with sizes several orders of magnitude smaller than traditional optical elements. These have already found applications in medical and astronomical imaging, augmented reality and, have been used by leading smartphone manufacturers such as Samsung and Apple in their cameras. Further advancement to this technology in terms of dynamic control is the need of the hour and can be enabled by active metasurfaces which allow dynamic tuning of optical properties. This project seeks to create highly versatile metalenses with diffraction-limited performance whose focal length can be tuned on demand non-mechanically. This will be done by employing a chalcogenide phase change material (e.g., Sb₂S₃) as the metalens platform which enables access to material states with different refractive indices. By switching the state of the phase change material from amorphous to crystalline and vice-versa, the optical response of the metalens can be dynamically reconfigured. The realization of such systems at visible frequencies have proven to be extremely challenging due to the complexity of identifying suitable nanostructures which can provide the required full 2π phase coverage across the different material states. We propose to work around this problem through a unique strategy that combines various factors such as choice of material platform as well as the design and optimization of the metasurface geometry. Furthermore, we will look to control the frequency dependent phase profile across different states of the material platform to realize achromatic metalenses with broadband operational capabilities. The results from this project are expected to yield novel metalens designs and also will cater to a range of applications particularly medical endoscopic imaging where dynamic tuning of the depth of focus is extremely important.