Ph.D Thesis

Ph.D StudentFrischwasser Jacob
SubjectNonlinear Interaction of Light with Subwavelength
Plasmonic Structures
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Guy Bartal
Full Thesis textFull thesis text - English Version


Incorporating optical surface waves in nonlinear processes is known to enable enhanced, sensitive and unique nonlinear interactions. Albeit not radiating to the far-field, the high field confinement, associated with surface waves, has a crucial role in the outcome of any nonlinear interaction in plasmonic, phononic and exitonic materials. This thesis implements fundamental nonlinear processes such as sum-frequency-generation and four-wave-mixing into nanophotonics where Surface Plasmon Polaritons (SPPs) are mixed with or excited by propagating light. By harnessing the metallic nonlinearities, we show how these of nonlinear interactions can be tailored and manipulated to provide novel applications and intriguing scientific phenomena.

The thesis is constructed of three main parts:

The first contains the theoretical background where we introduce the field of plasmonics and derive basic linear properties of SPPs. We also provide elaborated calculations of the nonlinear fields emanating from metals in a nonlinear process of Partially Degenerated Four-Wave-Mixing (PDFWM). We show the practical aspects of utilizing this process in nonlinear interactions with SPPs. It should be noted that the derivations provided in this chapter are rather general and a more elaborated and case-sensitive calculations are described independently in each of the following chapters.

The second chapter introduces a new method for near-field microscopy which relies on the nonlinear interaction between a photonic and plasmonic fields resulting in a photonic nonlinear emission. We analyze and demonstrate experimentally, how the nonlinear polarization in this case may radiate the plasmonic field pattern to the far-field thereby enabling both detection and processing of the near-field pattern using standard optical components. Moreover, we show that this kind of nonlinear interaction is polarization sensitive, giving rise to polarization-selective imaging of the plasmonic in-plane fields by merely toggling the photonic pump polarization.

In the third chapter we demonstrate a unique form of optical nonlinearity which we refer to as “dark nonlinearity” which is used to explore the influence of nonlinear polarization on short-range SPPs- the plasmonic states confined to the interface of a high-index substrate and a subwavelength metallic film. Contrary to most demonstrations of nonlinear interactions, dark nonlinearity generates a nonlinear polarization whose transverse momentum (wavenumber) is outside the light-cone thus prohibits far-field nonlinear emission. We utilize this form of nonlinearity to access the resonance and anti-resonance of short-range plasmons and characterize the traits of short-range plasmons under the influence of nonlinear polarization.