Fig. 5

a, b The absorption spectra when the periodicities of the PME patterns are tuned at normal incidence for Device A (a) and Device B (b). The integrated absorption efficiency in the active layer (η _I) versus the periodicity for Device A (c) and Device B (d) with the dashed line representing η _I for the control device. η _I versus the incident angle θ at TM or TE polarization for the optimal Device A (e) and Device B (f)