The Experts below are selected from a list of 9945 Experts worldwide ranked by ideXlab platform

J Martinez - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility analysis of a standalone Direct Pumping photovoltaic system for irrigation in Mediterranean greenhouses
    Renewable Energy, 2016
    Co-Authors: Juan Reca, R. López-luque, Carlos Torrente, J Martinez
    Abstract:

    The profitability of photovoltaic (PV) systems for irrigating Mediterranean greenhouse crops is analyzed. A standalone Direct Pumping PV system is proposed. A simulation model of the system was developed in order to obtain the economically optimal design of this system and evaluate its feasibility. The model is composed of several submodels: the photovoltaic power generation capacity submodel, the Direct Pumping management submodel and the submodel that evaluates the irrigation water requirements for a representative greenhouse and the overall economic performance of the system.The effect of the total number of irrigation sectors per hectare on the performance of the system has been analyzed. Two management strategies have been considered: to irrigate with only one irrigation sector simultaneously or to irrigate with a variable number of irrigation sectors as a function of the incoming power provided by the PV array. The optimal operation strategy provided by the model was the first one as the second was penalized by the higher cost of the pumps. The system becomes profitable for at least 4 sectors per hectare. The profitability and energy use efficiency of this type of systems are relatively low, although these values could be improved if the excess of energy were used for other purposes, such as ventilating or cooling the greenhouse.

  • optimal design of a standalone Direct Pumping photovoltaic system for deficit irrigation of olive orchards
    Applied Energy, 2015
    Co-Authors: Rafael Lopezluque, Juan Reca, J Martinez
    Abstract:

    In this work, an optimal standalone Direct Pumping photovoltaic irrigation system is proposed for the deficit irrigation of olive orchards. A simulation model of the system was developed in order to obtain the economically optimal design of this system. This model is composed of different sub-models: the photovoltaic power generation capacity sub-model, the Direct Pumping management sub-model and the sub-model that evaluates the economic and productive response of the crop to the application of water. The model simulates for increasing values of peak power of the photovoltaic system, the water and energy balance in the photovoltaic irrigation system and the crop yield. It also calculates the investments and operational costs of the system and, finally, the net economic returns to the farmer. The model enables us to select the optimal design of the system that achieves its maximum economic profitability.

S A Babin - One of the best experts on this subject based on the ideXlab platform.

  • 954 nm raman fiber laser with multimode laser diode Pumping
    Laser Physics Letters, 2016
    Co-Authors: Ekaterina A Zlobina, S I Kablukov, Ilya N Nemov, S A Babin, M I Skvortsov
    Abstract:

    CW Raman fiber laser emitting at 954 nm under Direct Pumping by a high-power multimode laser diode at 915 nm is demonstrated. A cavity of the laser is formed with 2.5 km-long multimode graded-index fiber and two mirrors: highly reflective fiber Bragg grating (FBG) at one side and normally cleaved fiber end at the other side. The laser generates low-index transverse modes at the Stokes wavelength with output power above 4 W at a slope efficiency above 40%. It is shown that utilization of a narrowband FBG mirror with low reflectivity instead of the cleaved fiber end with Fresnel reflection leads to stronger spectral mode selection, but the generated power is reduced in this case.

  • an ld pumped raman fiber laser operating below 1 μm
    Laser Physics Letters, 2013
    Co-Authors: S I Kablukov, E I Dontsova, Ekaterina A Zlobina, Ilya N Nemov, A A Vlasov, S A Babin
    Abstract:

    A CW Raman fiber laser (RFL) operating below 1 μm with Direct Pumping by a high-power multimode laser diode at 938 nm has been demonstrated for the first time. The laser cavity is formed by a normally cleaved fiber end and a highly reflective fiber Bragg grating (FBG) inscribed at the opposite end of a 4.5 km long multimode graded-index fiber. Low-index transverse modes are generated at the first Stokes wavelength of ∼980 nm with an output power of ∼3 W, while the second Stokes wave at 1025 nm also starts to be generated, thus limiting the 980 nm output.

Takunori Taira - One of the best experts on this subject based on the ideXlab platform.

  • thermally induced birefringence effects of highly nd3 doped y3al5o12 ceramic lasers
    Optical Materials, 2007
    Co-Authors: Ichiro Shoji, Takunori Taira, Akio Ikesue
    Abstract:

    Abstract Thermally-induced-birefringence effects of Nd:YAG ceramic lasers are accurately measured. Depolarization for the ceramics is found to be nearly the same with that for (1 1 1)-cut single crystals if Nd3+ concentration is the same. Under non-lasing condition, the thermally-induced birefringence becomes larger as Nd3+ concentration increases due to severer quenching. Under lasing, however, depolarization is measured to be one-third of that under non-lasing because the stimulated emission reduces the nonradiative process, which decreases the thermal load. Moreover, Direct Pumping into the emitting level by use of a 885 nm pump source intrinsically reduces the heat generation compared with the conventional 808 nm Pumping; we have experimentally verified that the depolarization and the thermal load are reduced by 30% by the Direct Pumping.

  • 1 34 μm efficient laser emission in highly doped nd yag under 885 nm diode Pumping
    Optics Express, 2005
    Co-Authors: N Pavel, V Lupei, Takunori Taira
    Abstract:

    We report on 1.34-μm laser emission in Nd:YAG under diode Pumping at 885 nm, Directly into the 4F3/2 emitting level. 3.8 W of output power with 0.26 overall optical-to-optical efficiency was recorded from a 2.5-at.% Nd:YAG single-crystal. Comparative results obtained by classical Pumping at 809 nm, in the highly absorbing 4F5/2 level, are presented, showing the advantage of the Direct Pumping. The influence of lasing wavelength and Nd concentration on the thermal effects induced by optical Pumping into the active component is discussed.

  • saturation factors of pump absorption in solid state lasers
    IEEE Journal of Quantum Electronics, 2004
    Co-Authors: Yoichi Sato, Takunori Taira
    Abstract:

    Novel models for the saturation factors of absorption under optical Pumping in solid-state lasers are derived, and these factors depend on the Pumping scheme. We investigated the pump saturation effect in Nd:YVO/sub 4/ and found that the bleaching of pump absorption due to the depletion of a ground-state level in a Direct Pumping scheme was more effective than that in a conventional four-level Pumping scheme. However, the saturation effect was recovered by lasing.

  • laser operation with near quantum defect slope efficiency in nd yvo4 under Direct Pumping into the emitting level
    Applied Physics Letters, 2003
    Co-Authors: Yoichi Sato, Takunori Taira, N Pavel, V Lupei
    Abstract:

    One-micron continuous-wave (cw) laser emission with 0.80 slope efficiency (0.79 optical-to-optical efficiency) under Ti: sapphire and 0.75 slope efficiency relative to absorbed power under diode-laser Pumping at 880 nm into the emitting level is demonstrated in a 1-mm-thick, 1.0-at. % Nd:YVO4 crystal. These values are superior to those obtained with 809-nm Pumping into the level 4F5/2, and can be explained consistently by the effect of the quantum defect between the pump and laser radiation, the superposition of pump and laser mode volumes, the pump-level efficiency and the residual optical losses. In the analysis of the 809-nm Pumping data a pump-level efficiency equal to the unity was employed, as determined with a method based on the pump-saturation effects on absorption.

  • highly efficient laser emission in concentrated nd yvo4 components under Direct Pumping into the emitting level
    Optics Communications, 2002
    Co-Authors: V Lupei, N Pavel, Takunori Taira
    Abstract:

    Abstract Reduction of the quantum defect in four-level lasers by Pumping Directly into the emitting level can improve laser emission parameters and diminish heat generation. Using concentrated components can compensate reduced absorption in the emitting level of Nd laser materials. These benefits are demonstrated by stable and highly efficient 1064 nm continuous-wave laser emission of Nd:YVO 4 components of 1, 2 and 3 at.% Nd under end-Pumping into 4 F 3/2 at 878.6 nm with a Ti:sapphire laser.

Juan Reca - One of the best experts on this subject based on the ideXlab platform.

  • Feasibility analysis of a standalone Direct Pumping photovoltaic system for irrigation in Mediterranean greenhouses
    Renewable Energy, 2016
    Co-Authors: Juan Reca, R. López-luque, Carlos Torrente, J Martinez
    Abstract:

    The profitability of photovoltaic (PV) systems for irrigating Mediterranean greenhouse crops is analyzed. A standalone Direct Pumping PV system is proposed. A simulation model of the system was developed in order to obtain the economically optimal design of this system and evaluate its feasibility. The model is composed of several submodels: the photovoltaic power generation capacity submodel, the Direct Pumping management submodel and the submodel that evaluates the irrigation water requirements for a representative greenhouse and the overall economic performance of the system.The effect of the total number of irrigation sectors per hectare on the performance of the system has been analyzed. Two management strategies have been considered: to irrigate with only one irrigation sector simultaneously or to irrigate with a variable number of irrigation sectors as a function of the incoming power provided by the PV array. The optimal operation strategy provided by the model was the first one as the second was penalized by the higher cost of the pumps. The system becomes profitable for at least 4 sectors per hectare. The profitability and energy use efficiency of this type of systems are relatively low, although these values could be improved if the excess of energy were used for other purposes, such as ventilating or cooling the greenhouse.

  • optimal design of a standalone Direct Pumping photovoltaic system for deficit irrigation of olive orchards
    Applied Energy, 2015
    Co-Authors: Rafael Lopezluque, Juan Reca, J Martinez
    Abstract:

    In this work, an optimal standalone Direct Pumping photovoltaic irrigation system is proposed for the deficit irrigation of olive orchards. A simulation model of the system was developed in order to obtain the economically optimal design of this system. This model is composed of different sub-models: the photovoltaic power generation capacity sub-model, the Direct Pumping management sub-model and the sub-model that evaluates the economic and productive response of the crop to the application of water. The model simulates for increasing values of peak power of the photovoltaic system, the water and energy balance in the photovoltaic irrigation system and the crop yield. It also calculates the investments and operational costs of the system and, finally, the net economic returns to the farmer. The model enables us to select the optimal design of the system that achieves its maximum economic profitability.

Ekaterina A Zlobina - One of the best experts on this subject based on the ideXlab platform.

  • Multimode Fiber Raman Lasers Directly Pumped by Laser Diodes
    IEEE Journal of Selected Topics in Quantum Electronics, 2018
    Co-Authors: Sergey A. Babin, Ekaterina A Zlobina, Sergey I. Kablukov
    Abstract:

    Raman fiber lasers (RFLs) are usually based on single-mode fibers core-pumped by high-power rare-earth-doped fiber lasers with single transverse mode output that leads to a rather complicated design of RFLs. One of interesting possibilities to simplify the RFL design is its Direct Pumping by cheap and reliable high-power multimode laser diodes (LDs). It is attractive to use standard graded-index multimode passive fibers characterized by very high quality and low cost due to their wide use in telecom. In this case, one can Directly couple the multimode radiation of high-power LDs with moderate brightness into the core of multimode graded-index fiber with much higher efficiency than into the core of single-mode fiber. Using commercially available multimode LDs with operating wavelengths of 915-940 nm, it is possible to obtain high-power high-beam-quality Raman lasing in wavelength range of 950-1000 nm, which is problematic for rare-earth-doped fiber lasers. Here, we review the results obtained in this Direction and report on the demonstration of all-fiber LD-pumped CW Raman laser based on the graded-index fiber. A joint action of Raman clean-up effect and mode-selection properties of special fiber Bragg gratings inscribed in the central part of fiber core, results in high-efficiency conversion of multimode (M2~26) pump at 915 nm into a high-quality output beam at 954 nm. Fibers with core diameter of 62.5, 85, and 100 μm are compared. With core enlargement, the conversion efficiency increases sufficiently (from 47% to 84%) at the expense of slight beam-quality parameter reduction (M2 = 1.3-3). The generated spectrum remains to be rather narrow (60 W.

  • 954 nm raman fiber laser with multimode laser diode Pumping
    Laser Physics Letters, 2016
    Co-Authors: Ekaterina A Zlobina, S I Kablukov, Ilya N Nemov, S A Babin, M I Skvortsov
    Abstract:

    CW Raman fiber laser emitting at 954 nm under Direct Pumping by a high-power multimode laser diode at 915 nm is demonstrated. A cavity of the laser is formed with 2.5 km-long multimode graded-index fiber and two mirrors: highly reflective fiber Bragg grating (FBG) at one side and normally cleaved fiber end at the other side. The laser generates low-index transverse modes at the Stokes wavelength with output power above 4 W at a slope efficiency above 40%. It is shown that utilization of a narrowband FBG mirror with low reflectivity instead of the cleaved fiber end with Fresnel reflection leads to stronger spectral mode selection, but the generated power is reduced in this case.

  • an ld pumped raman fiber laser operating below 1 μm
    Laser Physics Letters, 2013
    Co-Authors: S I Kablukov, E I Dontsova, Ekaterina A Zlobina, Ilya N Nemov, A A Vlasov, S A Babin
    Abstract:

    A CW Raman fiber laser (RFL) operating below 1 μm with Direct Pumping by a high-power multimode laser diode at 938 nm has been demonstrated for the first time. The laser cavity is formed by a normally cleaved fiber end and a highly reflective fiber Bragg grating (FBG) inscribed at the opposite end of a 4.5 km long multimode graded-index fiber. Low-index transverse modes are generated at the first Stokes wavelength of ∼980 nm with an output power of ∼3 W, while the second Stokes wave at 1025 nm also starts to be generated, thus limiting the 980 nm output.