Blue Pr(3+)-doped ZBLAN fiber upconversion laser

Concentration dependence of visible luminescence from Pr3+-doped phosphate glasses

To clarify the concentration dependence of visible fluorescence of Pr³⁺, a series of phosphate glass samples with Pr³⁺ concentration from 0.05 to 3.0 mol% were fabricated. Steady and dynamic spectroscopic characteristics of Pr³⁺-doped phosphate glasses were systematically investigated. When the Pr³⁺ concentration was small, only one visible fluorescence band can be observed at 596 nm, which was ascribed to the transition of ¹D₂ → ³H₄. With increasing Pr³⁺ concentration from 0.05 to 0.5 mol%, since the multi-phonon relaxation rate of ³P₀ was largely quicker than that of ¹D₂. Increasing Pr³⁺ concentration from 0.5 to 3 mol%, increasing two other fluorescence bands at 612 nm and 640 nm, which were assigned to the transitions of ³P₀ → ³H₆ and ³P₀ → ³F₂, respectively. It was due to the cross relaxation probability between [¹D₂: ¹G₄] and [³H₄: ³F₄] increased, which results in quicker decay rate of ¹D₂. The fluorescence lifetime of ¹D₂ decreased from 173 to 6 μs with increasing Pr³⁺ concentration from 0.1 to 3 mol%, which due to the cross relaxation probability between [¹D₂: ¹G₄] and [³H₄: ³F₄] increased, resulting in quicker decay rate of ¹D₂. Fitting the concentration dependence of fluorescence lifetime demonstrated that the cross relaxation arising from dipole-dipole interactions between Pr³⁺ ions.

Efficient continuous-wave and short-pulse Ho3+-doped fluorozirconate glass all-fiber lasers operating in the visible spectral range

In this work, efficient visible Ho³⁺-doped fluorozirconate glass (Ho:ZBLAN) all-fiber lasers operating in continuous-wave (CW) and Q-switching regimes are experimentally demonstrated. The combination of a direct blue pump, a highly-doped Ho:ZBLAN fiber and the fiber end-facet mirrors contributes to a simple all-fiber configuration. A tunable laser emission in the green spectral range of 543-550 nm is achieved with >150 mW output power and a tunable deep-red laser around 754-758 nm is also obtained with about 16 mW output power. Interestingly, stable visible self-Q-switched operation was successfully observed. For the green Q-switched all-fiber laser, a maximum single pulse energy of 196 nJ is realized with a repetition rate of 97.66 kHz and a pulse duration of 605 ns. As the pump power is increased, the deep-red Q-switched all-fiber laser has the pulse repetition rate from 59.88 to 100.5 kHz and the pulse duration from 4.85 to 2.02 μs, corresponding to the maximum pulse energy of 58 nJ. To the best of our knowledge, this work is the first demonstration of Ho:ZBLAN all-fiber lasers emitting in the visible spectral range (i.e., both green and deep-red wavelengths).

Comparative investigation on the spectroscopic properties of Pr³⁺-doped boro-phosphate, boro-germo-silicate and tellurite glasses

We report on the spectroscopic properties of Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses. The stimulated absorption and emission cross sections were estimated. Only one emission at 596 nm and 605 nm is observed in Pr(3+)-doped boro-phosphate and boro-germo-silicate glasses, respectively, while three emissions at 605 nm, 612 nm and 645 nm are observed in Pr(3+)-doped tellurite glass when excited at 467 nm. The fluorescence lifetime at 600 nm in Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses is 137 μs, 73 μs and 51 μs, respectively. The emissions from Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses show different decay behaviors and can be well explained by multiphonon relaxation theory.

Actively mode-locked visible upconversion fiber laser

Active mode locking of a Pr(3+)/Yb (3+) -doped upconversion fluoride fiber laser with an all-fiber ZnO acousto-optic phase modulator is demonstrated for the first time to the authors' knowledge. Optical pulses of ~550-ps duration with a repetition rate of 239 MHz at a wavelength of 635 nm have been generated.