Backward wave phenomenon for light propagating through a silver nanorod array

In this work, we use glancing angle deposition (GLAD) to fabricate a silver nanorod array. The average tilt angle and diameter of the silver nanorod are 65° ± 5 and 323 nm, respectively. When the array is illuminated by normal incident light, oscillating electric field parallel to the rod and perpendicular to the rod would induce the transverse and longitudinal plasmon resonant modes. As the longitudinal plasmon mode occurs, the absorption of the array with thickness 323nm is enhanced and the TM mode transmittance is reduced to be 0.3 percentages. The transmitted ellipsometric parameters are measured and the phase difference between TE mode and TM mode transmission coefficients is detected. The absolute transmission coefficient is measured by walk-off interferometer. Compared with the relative phase, the phase of TM mode transmission coefficient becomes a negative value. It is proposed here that a wave propagates through the "effective thin film" and acts like a backward wave in the film.