ABSTRACT
In this chapter, we will discuss a number of developments that, in our view, would be interesting to consider for the future of nonlinear metasurfaces. In Section 10.1, we will lay out an approach to gain an exquisite control over the phase and polarization of second harmonic light using electron beam lithography semiconductor metasurfaces. In Section 10.2, we will examine strategies that may be followed to produce overlooked and exotic nonlinearities. We will examine nonlinear phenomena for optical beams propagating parallel to the metasurfaces, which is at variance with the existing literature that mostly deals with out-of-plane nonlinear processes, and also consider the case of the strong coupling regime. Finally, in Section 10.3, we will argue that metasurfaces made of colloidal nanoparticles have a strong and as-yet untapped potential for fulfilling many of these goals (and also to serve as a powerful alternative to existing implementations) due to their ease of fabrication and high versatility.
