Research Projects

The three degrees of freedom of light (amplitude, phase, and polarization) interact among each other to generate several exotic optical effects. Among these effects spin-orbit interaction (SOI), similar to that of electron in solid deserves a special mention. However, despite the progress made in recent years, there are still some challenges that needs to be addressed in order to fully utilise the potential of SOI metasurfaces. SOI signals obtained is generally low and an amplification would improve the detection. One of the prevalent ways of enhancing the signal would be designing the desired wavelength of operation at the resonance of the metasurface. This can also be extended to include hybrid metasurfaces where the interplay of several modes can lead to enhancement of the effects at desired wavelength. Moreover, hybrid metasurfaces provides the additional advantages of tunability and control, where the geometry and the material of the nanostructures and the underlying substrate can be tailored to tune the resonances thus in turn the SOI effects. These hybrid metasurfaces also support several other exotic phenomenon like Fano resonance, and Extraordinary transmission (EOT) to name a few. At the heart of such optical effects lie near-field interference among the different components. It has been seen that the optical effects arising from near-field also enhance the SOI effects that can be detected in the far field. In this proposal we aim to probe the near field optical effects in hybrid metasurfaces experimentally with near-field scanning optical microscopy (NSOM) along with the far-field spectra measured conventionally. Since the origin of enhancement and tunability of SOI effects in hybrid systems can be majorly attributed to near-field interferences, we believe that probing them experimentally would lead to new and exciting insights into physics. Moreover, it would help us to understand how the evolution of the near-field to the far-field. We would also investigate the far-field parameters that are in direct relation with the near-field distribution so that we can formulate a direct relation with the properties of the near-field from the parameters measured in the far-field. Since far-field measurements are less complicated, conventional and cost-effective, a direct relation between the far-field spectra and the near-field distribution would be extremely helpful to the optical community. To the author´s knowledge, such a unique experimental study connecting the near and the far-field has not been conducted before. Finally, with the insights gained from our experiments, we would perform an educated design of improved and novel SOI metasurfaces where the near-field can be tailored precisely to enhance the SOI effects. These metasurfaces will also be fabricated in the nanofabrication facility of IISER Kolkata and would be incorporated into ``meta-devices" which are ultra-thin alternatives to traditional optical setups.