A fully planar solar pumped laser based on a luminescent solar collector

Abstract

A solar-pumped laser (SPL) that converts sunlight directly into a coherent and intense laser beam generally requires a large concentrating lens and precise solar tracking, thereby limiting its potential utility. Here, we demonstrate a fully-planar SPL without a lens or solar tracking. A Nd 3+-doped silica fiber is coiled into a cylindrical chamber filled with a sensitizer solution, which acts as a luminescent solar collector. The body of the chamber is highly reflective while the top window is a dichroic mirror that transmits incoming sunlight and traps the fluorescence emitted by the sensitizer. The laser-oscillation threshold was reached at a natural sunlight illumination of 60% on the top window. Calculations indicated that a solar-to-laser power-conversion efficiency could eventually reach 8%. Such an SPL has potential applications in long-term renewable-energy storage or decentralised power supplies for electric vehicles and Internet-of-Things devices.

Solar Pumping of Fiber Lasers with Solid‐State Luminescent Concentrators: Design Optimization by Ray Tracing

“…In simulations a reflectance of 45% is used for the edge surface of the light‐trapping chamber (see Figure 2a) in accordance with the reference design. [ 27 ]…”

“…To validate the data, the 30 mW absorbed power by Nd 3+ ions in the simulated reference design can be compared to experimentally determined small‐signal gain of 1.9 km −1 in the reference design. [ 27 ] The calculations are available in the Supporting Information (Section 3) and rely on the saturation intensity in the silica fiber. Two sources exist for saturation intensity, with a large discrepancy in the determined values (1.4 × 10 8 W m −2 , and 3.4 × 10 8 W m −2 ).…”

“…The absorption coefficient of the Nd 3+ ‐doped silica fiber core, also implemented in simulations, was obtained from transmittance measurements. [ 27 ] With a peak in the absorption coefficient of 3.8 cm −1 at a wavelength of 582 nm, the single pass absorption of the silica fiber (16 µm core diameter) is small (< 0.6%). The low scattering and absorption from the fibers embedded in an appropriate LSC leads to a homogeneous light density in the LSC and consequently a uniform pumping of the entire length of the fiber.…”

“…Previously, a functional SPL has been shown, based on a radiative energy transfer from a luminescent dye in solution, that does not require lenses, or mirrors, and solar tracking systems. [ 27 ] To realize this liquid‐LSC SPL, 190 m of Nd 3+ ‐doped optical fiber were coiled into a light‐trapping chamber (∅300 mm, 1.5 mm thickness). The chamber was filled with a 0.3 mmol L −1 solution of Rhodamine 6G (R6G) dye in methanol.…”

“…Then, the efficiency of power transfer to the Nd 3+ ‐doped silica fiber is determined; the designs are compared to the reference dye‐solution‐based SPL (mentioned in the introduction and that from now on will be referred to as the “reference design”). [ 27 ] The loss mechanisms, in each case, are explored. Thereafter, the optimum design and silica fiber length are determined as a function of the temperature‐dependent silica fiber losses.…”