1,720,976 research outputs found
Characterization and modelling of thulium:ZBLAN blue upconversion fibre lasers
No full textWe have investigated the performance of blue upconversion fibre lasers based on thulium-doped ZBLAN fiber, operating at 480 nm with a 1140-nm pump. Extensive fluorescence measurements have provided the necessary spectroscopic data to present a computer model that he performance of such lasers with good accuracy despite the complicated three-step upconversion mechanism and the influence of ion-ion energy transfer processes. We have identified the mechanisms that populate the levels above the 1G4 level and are able to specify the corresponding spectroscopic parameters. We discuss the relevance of these processes to the 480nm laser performance. Furthermore, we have calculated optimized parameters for such lasers
Ytterbium fiber lasers: versatile sources for the 1-1.2-µm region
No full textYtterbium doped silica fibers can offer very versatile laser sources in the 1-1.2-µm region with a wide range of possible pumps and operating wavelengths. In particular operation is possible from 980 nm to at least 1.18 µm. This range covers operation at 1.017 µm, suitable for up-conversion or for the 1.3 µm amplifier in Pr3+ ZBLAN fiber, and operation at 1.12 µm suitable for up-conversion in Tm3+ ZBLAN. We report here experimental results and modeling aimed at optimizing performance of Yb3+ fiber lasers for these various applications
Improved blue laser results and photochromic effects in Tm:ZBLAN fibre
No full textUpconversion lasing in Thulium-doped fluoride fibre has proved to be an efficient method of upconverting infrared light into blue laser emission and has been identified as a promising method of producing a compact short wavelength laser. There remains considerable scope for optimisation of performance, and we have been able to improve on previously reported results. However, attempts at optimisation by going to higher dopant concentrations have revealed interesting and unexpected photochromic effects. Optimisation of the output coupling has produced a slope efficiency for blue lasing output with respect to absorbed infrared power of 34% in 1000ppm Tm-doped fibre. Further, a diffraction grating has been used as an external tuning element and tuning of the blue output over a wavelength range of 475 to 486 nm has been achieved. To date the best results have all been achieved with fibres of very similar parameters; 1000ppm Tm-doped, NA = 0.2, single mode cutoff at 800 nm. We have recently investigated the effect of increasing the Tm concentration and have encountered a number of unexpected results. In more heavily doped fibres, pumping the Tm absorption at 1.14 µm, the optimum wavelength for upconversion pumping, results in an induced fibre loss across the visible spectrum. While this loss appears stable at room temperature it can be reversed by pumping with a significantly lower power at the same wavelength. The spectrum of the induced loss has been measured from 0.4 to 1 µm and the peak loss is dependant on the inducing power but has been measured as high as 20 dB/m. Such a loss has serious implications for lasing performance. Continuing work is aimed at discovering the source of this photochromic loss
Characterization and computer modelling of thulium doped upconversion fibre lasers
No full textThe Thulium ion in a ZBLAN host is a promising candidate for the implementation of fibre lasers utilizing several different upconversion schemes. Very efficient 480 nm lasing at room temperature has already been demonstrated with 1120/1140 nm pumping at Amoco [1] and in our group [2] where some new fibres are currently under investigation. Optimization of the performance requires a quantitative understanding of the system, including degrading effects especially at higher dopant concentrations of up to 10,000 ppm. We have measured not only the laser performance but also the steady-state fluorescence and the fluorescence decay of Tm doped ZBLAN fibres for various pump wavelengths. A detailed computer model, including the three-step excitation scheme as well various energy transfer processes between excited ions, has been developed and brought into good agreement with the experimental data. In this way we have clearly identified several new energy transfer processes. They were found to limit the performance of the 480 nm transition from the 1G4 level, but at the same time they should provide enough population in the 1D2 level for lasing at 455 nm and perhaps even 365 nm with a single 1140 nm pump. Unfortunately, we have also found a broad-band absorption induced by the infrared pump light; this effect seems to depend strongly on the Tm3+ concentration. It prohibited lasing at the mentioned wavelengths so far, but it could well be absent in new fibres which may be available soon. In this paper we will provide details of the computer model, and highlight those processes which play an important role in the various upconversion laser schemes. Other groups have achieved efficient lasing at 1.47µm and 810nm by pumping similar fibres with 1064nm [3, 4] although the ground-state absorption is very weak at this pump wavelength. To understand this is another goal of our work which is still in progress
Infrared-induced photodarkening in Tm-doped fluoride fibres
No full textWe have observed a new type of infrared-induced photodarkening in high-numerical-aperture fluoride fibers doped with 3000 and 10,000 parts in 106 by weight of Tm. The loss induced in the visible region by 1140-nm radiation is very strong (as high as 25 dB in a 50-cm piece) and broadband it can be removed by irradiation with the same pump wavelength at lower powers
Ytterbium-doped silica fibre lasers: versatile sources for the 1-1.2µm region
No full textYtterbium-doped silica fibers exhibit very broad absorption and emission bands, from ~800 nm to ~1064 nm for absorption and ~970 nm to ~1200 nm for emission. The simplicity of the level structure provides freedom from unwanted processes such as excited state absorption, multiphonon nonradiative decay, and concentration quenching. These fiber lasers therefore offer a very efficient and convenient means of wavelength conversion from a wide variety of pump lasers, including AlGaAs and InGaAs diodes and Nd:YAG lasers. Efficient operation with narrow linewidth at any wavelength in the emission range can be conveniently achieved using fiber gratings. A wide range of application for these sources can he anticipated. In this paper, the capabilities of this versatile source are reviewed. Analytical procedures and numerical data are presented to enable design choices to be made for the wide range of operating conditions
Recent advances in Yb<sup>3+</sup>-doped silica fibre lasers
No full textRecent advances in the operation of Yb3+-doped silica fibre lasers will be presented. including very efficient (up to 80%) cladding-pumped operation at 1020, 1040 and 1140nm, and the development of single-frequency sources for spectroscopic applications
Efficient upconversion laser action in Tm<sup>3+</sup> and Pr<sup>3+</sup>-doped ZBLAN fibres
No full textVisible wavelength lasers are much sought after for many applications. In this paper we report that significant powers at blue (46 mw), green (5 mw) and red (30 mw) are now available from Tm3+ and Pr3+-doped ZBLAN fiber lasers using very convenient pumping schemes based on the Yb3+-doped silica fiber laser
Improved laser performance of Tm<sup>3+</sup> and Pr<sup>3+</sup>-doped ZBLAN fibres
No full textIn this paper we present the performance of Tm3+ and Pr3+-doped ZBLAN fibre lasers at blue, green, and red wavelengths, both pumped efficiently with the output of Yb3+-doped silica fibre lasers
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