Excitation of Multiple Surface-Plasmon-Polariton Waves At Metal/Chiral-Sculptured-Thin-Film Interfaces

Open Access
Author:
Erten, Sema
Graduate Program:
Engineering Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Akhlesh Lakhtakia, Thesis Advisor
Keywords:
  • Surface plasmon polariton
  • Sculptured thin films
Abstract:
The objective of this research was to excite multiple surface-plasmon-polariton (SPP) waves guided by the interface of a metal and a chiral sculptured thin film (STF). For this purpose, three different experimental set-ups were used. The data were collected for several different samples. Aluminum, magnesium fluoride, zinc selenide and sodium fluoride are the materials that were used to deposit thin films. Both metal and chiral STFs were deposited by a thermal evaporation technique. In all cases, a 30-nm-thick aluminum film was deposited first on a pre-cleaned glass slide. Next, to deposit a chiral STF, the substrate holder in the vacuum chamber of the thermal evaporation system was tilted and rotated. The vapor flux angle, i.e., the angle between incoming vapor flux and the substrate plane, is called Xv. Chiral STFs deposited at Xv = 10 and Xv = 15 were used to understand the effects of different directions of the incoming vapor flux. Also, the thicknesses of chiral STFs were varied between 900 nm and 1500 nm. The chiral STFs were deposited in 3, 4, and 5 periods, each period being 300 nm in thickness. Besides chiral STFs, columnar thin films were deposited for comparison. A He-Ne laser was used as a light source to illuminate the sample which was affixed to a BK7 glass prism, and the reflectance was detected by a photomultiplier detector for both p- and s- polarizations of the incident light. Graphs of the reflectance versus the angle of incidence were plotted. If the angular location of a reflectance minimum is independent of the thickness of the chiral STF, then it is evidence of an SPP wave. Results of the experiments for Glass-slide/Aluminum/NaF-chiral-STF structure showed several reflectance minimums independent of the thickness of the chiral STF; hence, multiple SPP waves were launched. If more than one SPP wave can be launched guided by the interface of a metal and a thin film, this property can be used for many different applications including bio-chemical sensing.