Rare-earth doped Fabry-Perot microcavities by sol-gel processing

摘要

Since the launching of the photonic bandgap concept in 1987, the development of the corresponding structures has expanded very rapidly, in particular for two-dimensional semiconductor-based structures. In the case of sol-gel derived materials, the main emphasis has been on one-dimensional mutilayer stacks and, in particular, on three-dimensional structures of the opal and inverse opal type. In this work, one-dimensional multilayer stacks of periodically alternating low refractive index (SiO_2) and high index (TiO_2) materials have been deposited by spin-coating onto silica or single crystal Si substrates, in the form of dielectric mirrors (distributed Bragg reflectors) and Fabry-Perot microcavities, both single and coupled (double). Some of the microcavities were doped with rare-earth elements (Er and Yb). These structures have been characterized by X-ray diffraction, infrared spectroscopy and field emission-scanning electron microscopy; their optical properties have also been measured, namely the stop band of high reflectivity and, in the case of the microcavities, the cavity modes and the photoluminescence behavior of the rare-earth ions inserted in the cavity layers. The presence of Er in both cavity layers of coupled microcavities was found to lead to a substantial increase in photoluminescence signal intensity and width, compared to the cases where Er was present only in one of the cavities. The possibility of an antenna effect between Yb~(3+) and Er~(3+) ions is also examined.