Abstract:In this brief review we consider the main factors determining the oscillation spectral range of cladding-pumped ytterbium-doped fiber lasers (YDFLs) and the results obtained for lasers emitting at various wavelengths. Like erbium-doped fiber amplifiers we suggest dividing the oscillation spectral range of YDFLs into three bands, namely: convenient (C-band), short (S-band), and long (L-band). Polymer-coated double-clad fibers with the inner cladding having a size of more than 100 µm allows one to get efficient operation in the convenient range (Cband): 1060 − 1130 nm. To get an oscillation within the S-band (976 − 980 nm and 1020 − 1060 nm) it is necessary to use active fibers with a small square of the inner cladding. Heating of the active fiber gives the possibility to get lasing within the L-band λ > 1130 nm). Another way to get an emission in this spectral range is by the application of long-wave pumping by a C-band YDFL. Also, we indicate some features that require further study.
For the first time we have suggested and realized passive Q-switched cladding pumped Er-doped fiber laser with a saturable absorber based on Tm-doped fiber. The pulse duration was of 100 ns, the pulse energy -0.35 mJ, the peak power -3.5 kW while the average power is less than 1 W. The laser is perspective for technology processes and medicine. Key words: fiber laser and amplifier; Q-switching Q-switched fiber lasers due to high pulse energy allow one to increase a number of laser applications including medicine, material processing, range finding etc. Application of all-fiber design simplifies the laser collection and operation. One of the ways to realize all-fiber Q-switched laser consists in an application of the fiber saturable absorber. This approach utilizes an additional fiber having resonance losses at the oscillation wavelength within the laser cavity. Thus, Cr-doped fiber was used as absorber in Nd-doped fiber [1]. In [2,3] it was demonstrated that a placing of Sm-doped fiber in the cavity of Yb-doped fiber laser allows one to get the pulse generation occurring in extremely stable manner with pulse energy of approximately 20 μJ. A Q-switch pulse had a nearly perfect pulse shape with a ∼650 ns full width at half maximum (FWHM). The interesting approach was applied in [4], where Bi-doped fiber played a role of the saturated absorber. Bi-doped fiber was placed in a separate cavity to achieve a laser action at its wavelength and consequently to decrease the lifetime of the active centers in the excited state. That allowed authors to demonstrate the stable pulsed lasing with the pulse energy up to 0.1 mJ and the pulse duration in a range of approximately 1-2 μs. Application of this laser allowed us to demonstrate the pulsed Raman laser [5,6]. In [7,8] Q-switched Yb-doped fiber laser with Ho-fiber laser as the saturable absorber was demonstrated. Pulse energy was estimated as 70 μJ, peak power -as 300 W and pulse duration -250 ns. Thus several schemes for Q-switched Yb-doped fiber lasers were development.At the same time Q-switched Er-doped fiber lasers are of great interest because of their oscillation spectral range
Abstract:We have realized ytterbium fiber laser emitting at 1160 nm. To avoid a competition with a spontaneous lasing at shorter wavelengths we pumped laser into the core at wavelength of 1070 nm. Cladding pumped Yb-laser was used as a pump source. Also, the active fiber was heated up to 70• C to increase the absorption of the pump power and suppress the spontaneous emission. The lasing efficiency slope of 45% was measured. A maximum output power of 3.2 W was achieved.
An experimental and theoretical investigation of the nonlinear transmission coefficient in a set of Ytterbium-doped silica fibers (YFs) with various concentrations of Yb(3+) ions at continuous-wave 980-nm pumping is reported. An analysis of the obtained experimental data shows that YF transmission coefficient is notably affected by the presence of Yb(3+) - Yb(3+) ion-pairs in the fibers, especially in heavily-doped ones. The last fact is confirmed by the study of the cooperative luminescence and absorption effects in the fibers, where a detailed inspection of their dependence on Yb3+ concentration is presented. The pairs' effect is shown to seriously modify both the nonlinear character of YF transmission coefficient at lambda = 980 nm and Yb(3+) excited-state relaxation. A modeling of the experimental data is performed, which allows to find the coefficients addressing the pairs' effect in each of YFs under study and, as a result, to fit the experimentally measured dependences of YF transmission coefficient on pump power, fiber length, and Yb(3+) concentration.
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