We present preliminary results relating to laser emission at 3:16 µm from a Dy fiber laser that is diode pumped at 800 nm. To allow strong diode pump absorption and to capture improved quantum efficiencies resulting from cross relaxation, the Dy:ZBLAN fiber was co-doped with Tm ions in a 10 to 1 concentration ratio to Dy. A resonant energy transfer from Tm to Dy provides an inversion on the 6H13/2 to 6H15/2 transition. Maximum output power of 5.5 mW at a slope efficiency of 1.3 % was produced from a highly non-optimal arrangement. System performance is bench marked against well established resonant pumping of the Dy upper state. Measurement of fluorescence lifetimes of both dopants allows for qualitative assessment of the energy transfer efficiency. A potentially detrimental energy transfer mechanism is identified and discussed.
In this paper, we report the first (to the best of our knowledge) GaN laser diode, emitting at 445 nm, pumped dysprosium (Dy) doped ZBLAN fiber laser for yellow emission using a simple setup. In our yellow laser experiment, we have used a commercially available Dy-doped ZBLAN fiber, which is originally designed for mid-infrared lasers demonstration and not optimized for visible laser design, as a laser active medium. For yellow (∼576 nm) lasing, we have exploited the 4F9/2 to 6H13/2 laser transition of a Dy ion, which is a quasi four level system. The performance of the yellow laser system is investigated by using two different Dy-doped fiber lengths (0.6 m and 5.95 m). The measured lasing thresholds are 7 mW and 28 mW for 0.6 m and 5.95 m of Dy-doped fiber, respectively. However, the maximum laser slope efficiency with respect to absorbed pump power is only 2.3% for 0.6 m of Dy-doped fiber. The laser slope efficiency decreases to 0.9% and the threshold increases to 28 mW for 5.95 m of Dy-doped fiber, which are result of fiber background loss at the signal wavelength. In addition, we have observed the pump excited state absorption at 445 nm pumping wavelength and estimated the pump ESA cross-section via numerical simulation.
Mid-infrared (mid-IR) fiber lasers that are based on dysprosium (Dy) as the active laser ion provide emission in the wavelength range between 2.6–3.4 μm and can thus bridge the spectral gap between holmium (Ho) and erbium (Er) based mid-IR lasers. Another distinct feature is the wide choice of pump wavelengths (1.1 μm, 1.3 μm, 1.7 μm, and 2.8 μm) that can be used. To date, pump wavelengths shorter than 1.1 μm have not been reported and all demonstrated pump wavelengths apart from in-band pumping suffer from pump excited state absorption (ESA). In this paper, we report new excitation wavelengths, 0.8 μm and 0.9 μm, for Dy-doped mid-IR fiber lasers. We have measured 18.5% and 23.7% slope efficiency (relative to launched pump power) for 0.8 μm and 0.9 μm pumping wavelengths, respectively. By comparing the residual pump power of experimental and numerical simulation data of a 0.5 m Dy-doped fiber, we have found that these new excitation wavelengths are free from pump ESA. Moreover, the high power laser diodes are commercially available at these new excitation wavelengths; therefore, the realization of a diode-pumped Dy-doped mid-infrared fiber laser might become feasible in the near future.
The yellow spectral region has applications in medicine, ophthalmology, acne treatment, and ytterbium based optical clock, which is recommended as the secondary representation of System International (SI) second. Lasing in this spectral region can be achieved by using sum frequency and second harmonic generation, which are complex methods. Here, we have reported the first (to the best of our knowledge) GaN laser diode pumped dysprosium (Dy) doped ZBLAN fibre laser for yellow lasing using a simple setup. Due to the four-level system, the laser oscillation threshold is low and about 7.0 mW for 0.6 m of Dy-doped ZBLAN fibre. However, the maximum slope efficiency is only 2.3% with the available 2% output coupler. In our investigation, we have identified two possible factors, fibre background loss and pump excited state absorption, for such a low slope efficiency.
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