Impact of the annealing temperature on the optical performances of Er-doped Si-rich silica systems Impact of the annealing temperature on the optical performances of Er-doped Si-rich Silica systems
Résumé
Series of Er-doped Si-rich silicon oxide (SRSO:Er) layers were grown by magnetron sputtering at different temperatures from ambient to 500°C and then annealed between 600°C and 1100°C. They were characterized by spectroscopic and time-resolved photoluminescence (PL) measurements. Significant PL was detected at 1533 nm from the as-grown samples at T≥300°C excited by a non-resonant wavelength (476 nm), hence indicating the formation of Si-based sensitizers during the growth process. The PL intensity and the decay lifetime of Er 3+ ions were both greatly increased with the annealing temperature. An optimum temperature of annealing is obtained at 800°C, which is expected to favor the formation of very dense and small sensitizers. The fraction of Er coupled to sensitizers was found nearly 6-7 times higher than that reported so far in the literature. 1. Introduction The effective excitation cross section of Er 3+ ions in SiO 2 is increased by 10 3-10 4 with the insertion of Si-based sensitizers in the matrix. It was shown that an indirect excitation of Er 3+ ions occurs through Si nanoclusters (Si-nc) [1,2]. Such an energy transfer allows one to benefit from the broadband high absorbance of Si-nc for optical excitation and from the improved transport of carriers injected by electrical excitation. This paves the way to the achievement of Er 3+ population inversion by either optical or electrical pumping for integrated photonics, such as planar amplifier, laser, etc. Recent studies reported that, in conventional SRSO:Er materials, only a small fraction (<2%) of Er 3+ ions are effectively benefiting from the Si-nc-mediated excitation [3]. Such a low value is far from ensuring an inversion population of Er 3+ , but requires, on the contrary, more efforts and studies to enhance significantly the proportion of coupled Er in SRSO:Er samples. These latter are usually submitted to annealing processes to form Si nanoclusters (Si-nc) as sensitizers, to remove non-radiative defects and to activate (optically) the Er 3+ ions. Such a treatment may change, however, the structure of either the Si-based sensitizers or the Er 3+ ions. This work aims at investigating the influence of growth and annealing temperature on the optical properties of the SRSO:Er layers and to correlate it to the proportion of Er coupled to sensitizers.
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