T. Qiu

Generation of 9.3-W multimode and 4-W single-mode output from 7-cm short fiber lasers

We generate 9.3-W continuous-wave 1535-nm multimode output from a 7.0-cm short-length Er-Yb codoped phosphate fiber laser. A slope efficiency of 29% is obtained at pump powers below 27 W. Very high output power per unit fiber length of 1.33 W/cm is achieved. From another 7.1-cm Er-Yb codoped fiber laser, 4.0-W single-transverse-mode output with M/sup 2//spl ap/1.1 is generated.

Generation of watt-level single-longitudinal-mode output from cladding-pumped short fiber lasers

We generate as much as 1.6 W of continuous-wave 1550 nm single-longitudinal-mode output from a cladding pumped Er-Yb codoped phosphate fiber laser. This power is to our knowledge among the highest in single-longitudinal-mode fiber lasers. The narrowband fiber Bragg grating output coupler is demonstrated to be an effective element for providing the single-longitudinal-mode selection.

Short-length microstructured phosphate glass fiber lasers with large mode areas

We report fabrication and testing of the first phosphate glass microstructured fiber lasers with large Er–Yb-codoped cores. For an 11-cm-long cladding-pumped fiber laser, more than 3 W of continuous wave output power is demonstrated, and near single-mode beam quality is obtained for an active core area larger than 400 μm2.

Short cladding-pumped Er/Yb phosphate fiber laser with 1.5 W output power

We report experimental results on a high-power, cladding-pumped, heavily Er∕Yb co-doped phosphate fiber laser of very short length. Up to 1.5W cw laser power was obtained from an11-cm-long multimode-core active fiber with optimized input and output couplers, when pumped by a 15W diode laser at 975nm. The fiber laser was demonstrated at 1535nm with a linewidth <1.2nm, and a good beam quality of M2<3.

3-Dimensional thermal analysis and active cooling of short-length high-power fiber lasers

A fully 3-dimensional finite element model has been developed that simulates the internal temperature distribution of short-length high-power fiber lasers. We have validated the numerical model by building a short, cladding-pumped, Er-Yb-codoped fiber laser and measuring the core temperature during laser operation. A dual-end-pumped, actively cooled, fiber laser has generated >11 W CW output power at 1535 nm from only 11.9 cm of active fiber. Simulations indicate power-scaling possibilities with improved fiber and cooling designs.

Over 3 W high-efficiency vertical-external-cavity surface-emitting lasers and application as efficient fiber laser pump sources

We report on the design and fabrication of high-power, high-brightness diode-pumped vertical-external-cavity surface-emitting lasers. Over 3 W continuous wave fundamental transverse mode (TEM00) output at 980 nm with a high slope efficiency of 44% is demonstrated at room temperature. The diffraction-limited beam with M2 factor of 1.15 at high-power operation is achieved. A vertical-external-cavity surface-emitting laser operating near 976 nm with a diffraction-limited beam is used to pump the core of 3 cm long Er∕Yb-codoped single-mode phosphate fiber lasers. An output power in excess of 250 mW at 1535 nm with a slope efficiency of 29% is obtained without any cooling.

Short fiber lasers produce record power/length of 1.33W/cm

In this paper we present experimental results1 achieved with short (7 cm) phosphate fiber lasers which generate more than 9.3 W multimode and 4 W single mode output power. To our knowledge, the power generated per unit fiber length of 1.33W/cm represents a record in the fiber laser world. This research may enable the development of on-chip, wattlevel single-frequency light sources in the 1,550 nm wavelength band. High power fiber lasers are a hot topic.2 Most high power fiber lasers use silica fibers measuring several tens of meters in length. It is impractical for such lasers to be integrated into very compact devices, such as those produced on chips or small boards. What’s more, when single frequency output is needed, long fiber lasers are unsuitable because of the difficulties inherent in selecting a single frequency from their closely spaced longitudinal modes. Short fiber lasers, those with a cavity length measured in centimeters, promise single mode and single frequency operation. The maximum output power of a centimeters long fiber laser is limited for the most part to the milliwatt level3 because of the difficulty of increasing ion doping concentrations in the fibers and of achieving high pump absorption with a double-cladding pump scheme. By solving these problems, we were able to boost the output power of such fiber lasers by more than one order of magnitude. The schematic layout of the fiber laser is shown in the inset of Fig. 1. The phosphate glasses used for fiber fabrication have high solubility of rare-earth ions and low clustering effects, which allows us to increase the concentration of Er 3+ (1.1 10 26 ions/m3) and Yb3+(8.6 1026 ions/m3) ions without enhancing the detrimental quenching processes. To achieve the “chaotic propagation” of the pump which improves pump absorption, the fiber has a D-shaped clad and an off-center circular core. The core diameters of the multimode and single mode fiber lasers are 19 m and 13.5 m. The numerical apertures of the multimode and single mode fiber lasers are 0.17 and 0.07. The fibers have an inner clad diameter of about 125-130 m. For both single mode and multimode fiber lasers, we used fibers measuring 7 centimers in length. The fiber laser cavities were formed by dielectric coatings at the fiber ends and an output coupler. The performances of both lasers are plotted in Fig. 1. We obtained up to 9.3 W power from the multimode fiber laser with M2 < 3.5 and 4 W from the single mode fiber laser with M2 < 1.2. To our knowledge, these are the highest powers ever generated from multimode and single mode fiber lasers with fiber lengths shorter than 10 centimeters. In addition, we demonstrated a new side-pumping scheme compatible with short fiber lasers.4 We used six pump delivery fibers which provided inputs for 12 independent pump diodes at 976 nm. The side-pumped laser constitutes a 12 cm long circular fiber with 18 m core doped with the same Er-Yb concentrations as those of the end-pumped fiber lasers. The performance of this laser is shown in Fig. 1 by the triangular symbols. Up to 5 W output power with optical-to-optical slope efficiency of 24 percent was obtained from this laser. This work was supported by the MRI program under AFOSR contract.

Cross-relaxation energy transfer in Tm3+ doped tellurite glass

A self-calibrating fluorescence spectroscopy technique was applied to study cross-relaxation 3H4, 3H6 → 3F4, 3F4, and energy migration 3H4, 3H6 → 3F4, 3F4, of the Tm3+ Ions doped in the tellurite glass. These glasses are investigated for their use in realization of 2 micron fiber lasers. Micro and macro-parameters of the energy transfer and migration were calculated by the means of the model of phonon-assistant multi-polar interaction and hoping mode. Steady rate equation analysis was used to fit the experimental fluorescence ratio of samples with different concentrations. We found that high-order (dipole-quadrupole) interaction was the dominant mechanism in the energy transfer of Thulium ions.

Microstructured and multicore fibers and fiber lasers

Microstructured and multi-core fiber lasers were fabricated that have produced more than 1.3 W/cm at 1.5 mum. Near 2 W single frequency, single-transverse-mode output was demonstrated

Tm3+ doped tellurite glass microsphere laser

Wavelength of 2000 nm single mode microsphere laser from highly thulium doped tellurite glass microsphere was demonstrated by means of fiber taper coupling. Laser wavelength was red shift from the emission peak of thulium ions at 1800 nm.