Shape-engineered nanostructures for polarization control in optical near- and far-fields

Light-matter interactions on the nanometer scale have been extensively studied to reveal their fundamental physical properties [1-3], as well as their impact on a wide range of applications, such as nanophotonic devicesnanophotonic devices [4], sensing [5], and characterization [6]. Fabrication technologies have also seen rapid progress, for example, in controlling the geometry of matter, such as its shape, position, and size [7,8], its quantum structure [9], and so forth. Electric-field enhancement based on the resonance between light and free electron plasma in metal is one well-known feature [10] that has already been used in many applications, such as optical data storage [11], bio-sensors [12], and integrated optical circuits [13-15]. Such resonance effects are, however, only one of the possible light-matter interactions on the nanometer scale that can be exploited for practical applications. For example, it is possible to engineer the polarization of light in the optical near-field and far-field by controlling the geometries of metal nanostructures, which also offer novel applications that are unachievable if based only on the nature of propagating light. It should be also noticed that since there is a vast number of design parameters potentially available on the nanometer scale, an intuitive physical picture of the polarization associated with geometries of nanostructures can be useful in restricting the parameters to obtain the intended optical responses.