Hematoporphyrin derivative: experimental evidence for aggregated species

Absorption and fluorescence properties of hematoporphyrin derivative in different solvent systems are investigated. The presence of a large amount of stable aggregates is demonstrated. The existence of these aggregates represents one major difference between hematoporphyrin derivative and hematoporphyrin free base.     

Measurement of the energy transfer and upconversion constants in Er–Yb-doped phosphate glass

A simple method to measure the ytterbium-to-erbium energy transfer and the co-operative upconversion constants in a phosphate laser glass is proposed. The technique is based on the experimental acquisition of the luminescence decay from the Er3+ 4I13/2 metastable level at 1.5m as a function of time and on a suitable fit of the experimental data. The fitting procedure relies on a simplified model of the Er–Yb system and makes use of a numerical solution of the rate equations to describe the dynamics of the populations, showing considerable sensitivity to the fitting parameters. The results obtained are in fairly good agreement with previous data reported in the literature.     

Passive mode locking of an in-band-pumped Ho:YLiF4 laser at 2.06 μm

We demonstrate the passive mode-locking operation of an in-band-pumped Ho:YLiF(4) laser at 2.06 μm using a semiconductor saturable absorber mirror based on InGaAsSb quantum wells. A transform-limited pulse train with minimum duration of 1.1 ps and average power of 0.58 W has been obtained at a repetition frequency of 122 MHz. A maximum output power of 1.7 W has been generated with a corresponding pulse duration of 1.9 ps.