Absorption coefficient (colored lines) as a function of photon energy. Solid lines are for α1(ℏω). Dashed lines are for α3(ℏω,I), and dotted lines are for α(ℏω,I) = α1(ℏω) + α3(ℏω,I). The results are for R1 = 10 nm, R2 = 20 nm, F = 0, P = 0, and I = 2×104W/cm2. Several values of the height of the ring have been considered.
Barseghyan et al. Nanoscale Research Letters 2012 7:538 doi:10.1186/1556-276X-7-538