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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2006. V. 9, N 3. P. 049-055.
Electromagnetic resonance absorption in metallic gratings
1Lviv Polytechnic National University, 12, Bandera str., 79013 Lviv, Ukraine
Phone: +38 0322 582581, e-mail: polyana@polynet.lviv.ua
Abstract. Reflection of electromagnetic waves with the 1.5 μm length from a metallic
grating (silver) with rectangular groove profile was analyzed using the method of
coupled waves. Appearance of the waveguide effect in a dielectric film and, accordingly,
of electromagnetic field resonance is a necessary condition of resonance absorption at
presence of dielectric thin film on the grating. The electromagnetic field resonance
phenomenon confirms a dependence of reflection on the wavelength, which is described
by the Lorenz function. When the film is absent, strong absorption is possible at
appearance of the waveguide effect between both grating metallic vertical walls. Due to
plasma resonance, both the waveguide effect and, accordingly, high absorption arise at
any distance between metallic walls of grating (slot width) for TM polarized waves. For
this polarization in the slot of 0.478 μm width filled with dielectric with permittivity
ε = 9 , the two waveguide modes propagate. That fact is confirmed by a dependence of
reflection logarithm on the grating depth. For TE polarized waves in the slot of 0.378 μm
width, the waveguide effect is possible on one mode only. The spectral dependence of
reflection for TE polarized waves is well described by the Lorenz function, and due to
excitation of two waveguide modes some deviation from this function is observed for
TM polarized waves. The dependence of the reflection index on the grating depth
completely agrees with the constant of waveguide mode propagation in the grating slot.
Keywords: resonance absorption, diffraction grating, coupled waves method, waveguide
effect.
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