טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentStav )Satuby( Yinnon
SubjectPlasmonics Planar Waveguiding Based Nanophotonics
DepartmentDepartment of Electrical Engineering
Supervisor Professor Meir Orenstein
Full Thesis textFull thesis text - English Version


Abstract

The interface between materials having positive and negative dielectric constants (dielectric-metal) can guide Surface Plasmon Polaritons (SPPs) optical waves, transverse magnetic (TM) polarized.

SPP waves confined to such interfaces are bearing a sub-wavelength penetration depth into both media, thus offering light a gateway to the world of nano dimensions and are at the core of research in nanophotonics.

In the framework of this research, photonic SPP devices were fabricated using gold as the main metal, in conjunction to Silicon, SiO2 or polymers as the dielectric substances. The devices were tested mainly at the telecom wavelength of l =1.55mm, as well as at a wavelength of l = 0.633mm. Measurement used both standard Microscopy and Near field Scanning Optical Microscope (NSOM). Results were compared to electromagetic analytical and numerical wave analysis.

Devices based on thin (20nm) gold stripes, embedded in a symmetrical polymer cladding, exhibited Long-Range-SPP waves. In this work, unique multi-mode SPP’s guided along wider stripes were recorded, having optical localization at stripe’s edge. A novel complementary structure of a slot made in that thin gold foil was experimentally characterized, and numerically validated as a new SPP supporting geometry.

Another novel structure proposed, is of trenches engraved in thick (400 nm) gold slab, within a homogenous surrounding. Resulting long propagating SPP modes different than the thin slot geometry, characterized by an inside trench TE polarized main lobe, matching the numerically resolved characteristics of such SPP waveguide.

Using thick gold layers enabled also fabrication of a ‘gap’ waveguides; trapping SPP waves in a thin dielectric layer in-between semi-infinite like metal cladding, as well as on top of V-grooves geometry, to facilitate ‘channel SPP waveguide’, characterized for its modal and polarization characteristics.

Asymmetrical dielectric-metal-air structured SPP waveguides were also formulated, as the upper air cladding enabled NSOM assisted optical characterization of features on the nano scale. Nano-photonic devices were fabricated using Focused Ion Beam milling and their NSOM characterization was validated by finite element modal calculations. In particular, SPP waveguiding along sub-wavelength slots and stripes, of moderate width/depth aspect ratio, as well as coupling schemes between the two, are innovative to this work, as those were designed fabricated and measured.

Utilizing nano-metallic inclusions to facilitate, artificial meta-materials possessing both negative permittivity and permeability, also known as Left-Handed-Materials, was theoretically looked into, studying an original concept of using such materials as the cladding of a dielectric sub-wavelength ‘gap’, thus enabling Left-handed waves to be guided within a dielectric core.