Light Management for Enhancing Optical Gain in a Solar‐Pumped Fiber Laser Employing a Solid‐State Luminescent Solar Concentrator

Abstract

The direct conversion of broadband solar radiation into highly coherent laser radiation has attracted scientific and practical interest in recent years. [1] After the first demonstration of a solar-pumped laser (SPL) in 1963, [2] subsequent studies were focused on improving the laser medium and the solar collector design, thereby achieving state-of-the-art high-power SPLs with solar collecting efficiency of up to 32.5 W m À2 (laser output power per unit area of the solar collector optics). [3,4] Such state-of-the-art SPLs comprised laser media, such as Nd 3þ -doped single-crystal yttrium aluminum garnet (Y 3 Al 5 O 12 ) rods, which were pumped by concentrated sunlight (the concentration factors were in the order of thousands). [5][6][7][8][9] SPLs exhibit many potential applications, including solar hydrogen generation, photovoltaic energy conversion, space solar power systems, space propulsion, and remote area telecommunications. [1,[10][11][12][13][14][15][16][17] In addition, SPLs with 20 kW output powers could be achieved by exploiting megawatt-scale solar furnaces; these SPLs could be employed in a fossil-fuel-free energy cycle in which magnesium is chemical energy storage for sunlight. [1,[18][19][20] Despite the range of potential applications, the utilization of highly concentrated sunlight has severely restricted the practical applications of SPLs owing to their dependence on an accurate solar tracking system. [21] Further, only the direct components of sunlight can be harvested by concentrating optical elements, such as lenses or mirrors; they do not function efficiently under cloudy conditions when the diffuse component of sunlight is high. Regarding locations, including Susono (Japan) and Karlsruhe (Germany), diffuse horizontal solar radiation represents %49% of the total terrestrial sunlight averagely received annually. [22] Furthermore, removing the reliance of SPLs on concentrating optics would further render the technology comparable with that of photovoltaic panels, thus availing new applications for SPLs since the modularity of such flat-plate devices would also favor small-scale applications. [23][24][25] Although SPLs, which do not require a mirror/lens-based concentrator system, have been studied for a long time since their introduction in 1983, [26] the technology was only demonstrated T. Masuda Carbon Neutral development division Toyota Motor Corporation

Luminescent solar concentrators for building integrated photovoltaics: opportunities and challenges

“…124 The latter price is based on a 25 mm layer thickness and even though the application was very different (part of a corrosion resistant layer stack for steel bridges 124 ), it is very similar to the 30 mm layers successfully used for LSC-pumped solar lasers. 125 (iv) Solar cells: as described in Section 2 (LSC Simulation Framework), the highest efficiency c-Si solar cells were selected for edge attachment. These 26.7% efficient devices are assumed to be cut into long strips that are 0.3 cm wide, thus a 1 m 2 LSC will require 120 cm 2 (0.012 m 2 ) of solar cells to cover all four edges.…”

“…124 The latter price is based on a 25 μm layer thickness and even though the application was very different (part of a corrosion resistant layer stack for steel bridges 124 ), it is very similar to the 30 μm layers successfully used for LSC-pumped solar lasers. 125…”

Solar-pumped fiber laser using a solid-state luminescent solar collector

“…The DM/HRM is the same as in the liquid LSC; however, its confinement efficiency is dramatically improved when the top layer of the dielectric multilayer is in contact with air. Although efficient light confinement is expected from total internal reflection (TIR) between the LSC and air [23], previous research has shown that DM/HR is a necessary component, with 40% of all photons confined by TIR, while the remaining 60% are confined by DH/HRM [22].…”

Solar-pumped fiber laser using a solid-state luminescent solar collector

“…We have already demonstrated the tunability of the fluorescence wavelength in preliminary experiments, and laser oscillation was accomplished under 50× sunlight with a primary concentrator [20]. To address the second problem, we then propose the use of solid-state LSCs [21,22]. Fig.…”

“…The film thickness was 80 μm, and the density was adjusted such that the optical density (OD) at a wavelength of 532 nm was 0.6. For details of the dye film, refer to previous studies [21,22].…”