Fig. 4
a Experimental transmission spectrum of the MCAs on sapphire substrate with the shell thickness of 60 nm. b The corresponding reflection spectra of MCAs on a silicon substrate, compared with the bare silicon substrate. c The photo-responsivities in the device with or without (control) MCAs’ decoration under 850 nm LED light illumination. d The corresponding enhancement ratio calculated from c. The background within the on-resonance and off-resonance region in b and d referring to the reflection spectra in b was highlighted in light red and light green, respectively