title: Polarization interferometry for real-time spectroscopic plasmonic sensing.
abstract: We present quantitative, spectroscopic polarization interferometry phase measurements on plasmonic surfaces for sensing applications. By adding a liquid crystal variable wave plate in our beam path, we are able to measure phase shifts due to small refractive index changes on the sensor surface. By scanning in a quick sequence, our technique is extended to demonstrate real-time measurements. While this optical technique is applicable to different sensor geometries-e.g., nanoparticles, nanogratings, or nanoapertures-the plasmonic sensors we use here consist of an ultrasmooth gold layer with buried linear gratings. Using these devices and our phase measurement technique, we calculate a figure of merit that shows improvement over measuring only surface plasmon resonance shifts from a reflected intensity spectrum. To demonstrate the general-purpose versatility of our phase-resolved measurements, we also show numerical simulations with another common device architecture: periodic plasmonic slits. Since our technique inherently measures both the intensity and phase of the reflected or transmitted light simultaneously, quantitative sensor device characterization is possible.
authors: Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Lauren M
authors: LM
authors: Otto
authors: Daniel A
authors: DA
authors: Mohr
authors: Timothy W
authors: TW
authors: Johnson
authors: Sang-Hyun
authors: SH
authors: Oh
authors: Nathan C
authors: NC
authors: Lindquist
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004867:Equipment Design; D006046:Gold / Q000737:chemistry; D007368:Interferometry / Q000295:instrumentation; D008853:Microscopy; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold