Transmittance (a) and photoluminescence (b) spectra of a porous silicon microsphere of about 4.1-μm diameter. Dips in the transmittance spectrum correspond to the peaks in the photoluminescence spectrum. They are associated to the optical resonances of the microcavity (reprinted with the permission of ).
Ramiro-Manzano et al. Nanoscale Research Letters 2012 7:497 doi:10.1186/1556-276X-7-497