892 research outputs found
Fiber design for high-power low-cost Yb:Al-doped fiber laser operating at 980nm
No full textWe investigated an Yb:Al-doped depressed-clad hollow optical fiber (DCHOF) for cladding-pumped 980nm laser operation. With a careful design, the nonzero fundamental-mode cutoff characteristics of a DCHOF allows the competing 1030-1060nm emission to be filtered out, despite being quite close to 980nm. The laser yielded over 3W of output power in a diffraction limited beam (M -parameter degrades to 2.7, as a result of increased cladding-mode lasing, as the cladding thickness is reduced
Advances in active fibres for high-power and high-brightness fibre sources
No full textThis paper reviews the progress in rare-earth doped fibre technology towards power scaling of high-brightness fibre sources
Bismuth doped fibres for near-infrared light sources: progress and prospects
No full textThe luminescence properties of Bi-doped silica fibres in the near-infrared region are discussed. Bi-doped fibre lasers and amplifiers and their dependence on the unsaturable loss and excited state absorption are also discussed
Impact of energy-transfer-upconversion on the performance of hybrid Er:YAG lasers
No full textUsing a hybrid fiber-bulk laser scheme based on Er:YAG, we have achieved ~60 W and ~30 W of continuous-wave output at 1645nm and 1617nm respectively, and Q-switched pulse energies up to ~30 mJ (limited by coating damage). Investigation of various factors influencing laser performance has revealed that energy-transfer-upconversion can have a very detrimental impact on efficiency, even in continuous-wave mode of operation. In this paper we report on the results of this study, discuss various measures for reducing energy-transfer-upconversion and its effect on laser performance, and consider the prospects for further increase in output power and pulse energy
High power in-band pumped Er:YAG laser at 1617 nm
No full textLaser sources operating in the eyesafe wavelength regime around 1.5-1.6 µm have applications in a number of areas including, remote sensing, ranging and free-space communications. For many of these applications, the requirement for high output power is often supplemented by the need for high efficiency and good beam quality. This combination of operating characteristics is very difficult to achieve in conventional diode-pumped solid-state lasers based on erbium doped crystals (sensitised with Yb) owing to the relatively high fractional heat loading which results from the large quantum defect (~ 40%) and energy-transfer-upconversion. To alleviate this problem, attention has recently turned to singly-doped crystals (e.g. Er:YAG) and in-band pumping using an Er,Yb fibre laser. This approach has the advantage that most of the waste heat is generated in the fibre, which is largely immune to thermal effects, and quantum defect heating in the Er-doped crystal is very small (~7%). Using this hybrid laser scheme, we have demonstrated ~60 W of continuous-wave output from an Er:YAG laser at 1645 nm with a slope efficiency of 80 %1. However, for some remote sensing applications this operating wavelength is a little inconvenient, since there are atmospheric absorption lines due to methane which are in very close proximity necessitating careful selection and control of the lasing wavelength. Er:YAG also has a transition from the same upper level manifold (4I13/2) at 1617 nm, which lies in a region of the spectrum where there are no atmospheric absorption lies. However, this transition has a much more pronounced three level character and hence a much higher threshold pump power, so it has received little attention in spite of its obvious advantages for certain applications. Here, we report preliminary results for power scaling of an Er:YAG laser at 1617 nm in-band pumped by a high-power cladding-pumped Er,Yb fibre laser
Multi-trench Fiber for high power laser applications
No full textOptical fibers have realized their immense potential for high power applications in the last decade. However, non-linearity still remains a challenge for power scaling for fiber lasers [1]. A large effective area of the fundamental mode of the optical fiber can increase the threshold of the non-linear effects [2]. However, simply increasing the core size leads to multi-mode operation and hence deteriorates the beam quality. Several novel optical fiber designs have been proposed to offer a large effective area of optical fibers such as Low NA Step index fibers, Photonic Crystal Fibers, Bragg Fibers, etc., while still maintaining single mode operation. Recently, we proposed a novel multi-trench fiber (MTF) design for large effective mode area, as shown by a cross-section schematic and a refractive index profile design in Fig. 1. [3]. This fiber design offers advantages of relatively easy fabrication, splicing, and cleaving. Numerical simulations reveal that the MTF fiber geometry can provide single-mode operation with a core diameter as high as 100µm with an effective area of ~ 10,000µm2 in a rod-type configuration and ~800µm2 in a bend configuration. A 30µm diameter core MTF has been fabricated and the cross-section and measured refractive index profile is shown in Fig. 2. S2 measurement shows ~50dB suppression of higher order modes (HOM) in a one meter length of fiber. Also, an ytterbium-doped single-trench-fiber laser (slope efficiency ~85%) with a 20µm diameter core has been experimentally demonstrated with very high suppression of HOM (~32dB), which was also verified by S2 measurement. The refractive index profile, plot of laser slope efficiency, an output beam profile and a laser output spectrum are shown in Fig. 3
High power fiber based sources
No full textFiber lasers and amplifiers offer unique characteristics that derive from the use of a waveguide and the properties of rare-earth doped glass. In the past few years, the fiber lasers and amplifiers have advanced from low-power systems for telecommunication applications to multi kW level sources suitable for industrial applications such as materials processing. Advances in high-power multimode diode and fiber technology, and the inherent power scalability of cladding-pumped fibers, lie behind this rapid surge. This talk will cover introduction to fiber lasers and amplifiers, recent developments in this field, up to date results, and future prospects
Tunable single-frequency ytterbium-sensitized erbium-doped fiber MOPA source with 150W (51.8 dBm) of output power at 1563 nm
No full textA single-frequency, single-mode ytterbium-sensitized erbium-doped fiber master-oscillator power-amplifier generated 150 W of continuous-wave output power at 1563 nm with 33% slope efficiency and was tuned in the range of 1546 to 1566 nm at >125 W
Bismuth doped fiber laser performance on effective fiber cooling
No full textIn the past, bismuth doped fiber (BiDF) lasers, operating in the 1160-1300 nm wavelength range, have gained much attention as they are promising for many applications; including medical and astronomy. However, the poor lasing efficiency of BiDF laser, compared to the widely used rare-earth doped fiber lasers, requires further investigations. One possible reason that can impair the BiDF laser efficiency is the presence of high unsaturable loss in the fiber, which is temperature dependent. Thus, temperature rise in the BiDF under strong pumping can be a limiting factor for such laser systems. Here, we report the dependence of BiDF laser efficiency on effective cooling of the fiber
Measurement of photodarkening in Yb-doped aluminosilicate fibres at elevated temperature
No full textPhotodarkening behaviour in Yb-doped aluminosilicate fibres at elevated temperatures is reported. The fibre was core-pumped at 977 nm and the transmitted powers were monitored at 633 (probe) and 977 nm (pump) simultaneously with ~47% of population inversion of Yb3+ ions. A saturated photodarkening loss was found, which is inversely proportional to temperature and, at ~573 K, the loss was negligible at the pump wavelength. From the decay curves at different temperatures, it was found that the photodarkening involves second-order kinetics to form colour centres
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