Enhancement and suppression of energy transfer from Si nanocrystals to Er ions through a control of the photonic mode density

The rate of energy transfer from Si nanocrystals to Er ions was modified by placing a Au layer nearby. The distance between the active layer and the Au layer as well as the wavelength were changed systematically to quantitatively discuss how the energy transfer rate is modified by the photonic mode density. It was found that at particular combinations of the spacer thickness and the wavelength the energy transfer was strongly suppressed, while at other combinations it was enhanced. In order to understand the oscillation behavior of the energy transfer rate, a model fitting was performed. By assuming that the energy transfer rate is proportional to the square of the photonic mode density, the observed oscillation behavior could be well reproduced, and from the fitting the energy transfer rate could be estimated. The estimated rates of energy transfer to the I-4(11/2) and I-4(9/2) states of Er3+ were about 31 and 5.7 ks(-1), respectively.