|Ph.D Student||Vander Roman|
|Subject||Surface Plasmon Resonance Imaging|
|Department||Department of Physics||Supervisor||Professor Emeritus Stephen Lipson|
|Full Thesis text|
Surface plasmons (SP) are electromagnetic waves that propagate along the interface between dielectrics and conducting layer and can be excited by p-polarized light only. The importance of surface plasmons lies in the fact that their propagation properties are strongly affected by the presence of a dielectric contacting the metal surface. Even an atomic dielectric layer will change the angle of excitation (SPR angle) by a measurable amount, this fact making techniques based on surface plasmon resonance (SPR) much more sensitive than other optical measuring techniques for thin films, such as interferometry and ellipsometry.
The SPR techniques are classified into 3 groups: a) scanning angle SPR , where excitation is obtained by monochromatic illumination and the reflected intensity is measured as a function of incident angle; b) SPR wavelength shift, where the set up is illuminated at fixed incident angle and the reflectivity is measured as a function of wavelength; c) SPR imaging, where the set up is illuminated by a monochromatic p-polarized plane wave at angle near the SPR angle, and the reflected light is detected by a CCD camera to produce the SPR image of the surface.
Because of its low and anisotropic spatial resolution, the regular SPR imaging technique has had little impact as a research tool. This resolution is limited in the direction of surface plasmon propagation by the propagation length, typically of the order of tens of microns. In the perpendicular direction the resolution is limited by diffraction limit of imaging optics only.
We proposed a new SPR microscopy technique that is based on Koehler illumination and the radial polarizing device that was developed and patented in our lab. This set up illuminates the sample with uniformly collimated p-polarized monochromatic light from all spatial directions. This fact provides us with an isotropic spatial resolution, which is not limited by the plasmon propagation length and, theoretically, will be equal to the diffraction limit of our optical set-up.
The theory of this approached is presented, supported by simulations and confirmed experimentally by measurements with a resolution target.