Observation of Surface Plasmons in Subwavelength Gratings

     The interest in subwavelength gratings is growing due to their promising applications in high performance transmission and reflection filters, optoelectronic devices using surface plasmons, spectral-selective external... [ view full abstract ]

     The interest in subwavelength gratings is growing due to their promising applications in high performance transmission and reflection filters, optoelectronic devices using surface plasmons, spectral-selective external optical mirrors for lasers (VCSELs). Such structures for the complete absorption of radiation in the far IR region were considered in [1]. In [2] subwavelength gratings were proposed and demonstrated for combining red, green and blue light beams into a single beam.

      In the present work it is shown that the effect of full absorption can be also observed in sub-wavelength metallic gratings for radiation in the visible range of the spectrum. Diffraction of light of a visible spectral range by subwavelength metal gratings (Fig. 1) is investigated theoretically and experimentally. The influence of different grating parameters (filling factor, shape and depth, material, angle of incidence, wavelength and polarization of radiation) on the diffraction efficiency is investigated. High diffraction efficiency in the -1st order is observed with increasing depth of the grating relief (more than 70% at a depth h = 80 nm). It is shown that under certain conditions an effect of plasmon resonance occurs, at which a complete absorption of the incident radiation takes place. The considered optical elements can be used in systems for image processing, projection displays, in the development of a variety of sensors, etc.

In Fig. 2 the results of calculations and measurements of diffraction efficiency of the zero order of the nickel grating depending on the angle of incidence of radiation with p- polarization are presented. It is seen that the effect of plasmon resonance at the incidence angle of ~33^o takes place. With a relief depth of h = 80 nm and angle of incidence = 31^o almost all incident energy is absorbed by the grating. This property can be used to develop various devices, in particular, in solar cells and displays.

Acknowledgement: This research was supported by the Russian Science Foundation (project No. 17-19-01461).

References

1. Vial B., Demesy G., Zolla F., et.al. JOSA B. 2014. V.31. p. 1339-1346.

2. Petrov N.I., Nikitin V.G.., Danilov V.A., Popov V.V., Usievich B.A.  Applied Optics. 2014. v.53. p.5740-5744.