Solar Pumped Fiber Lasers Research Articles

Fully planar solar-pumped fiber laser with 0.1% slope efficiency.

A slope efficiency of 0.1% has been achieved for a fully planar solar-pumped fiber laser (SPFL) with a diameter of 30 cm and an output power of 34 mW. The fiber length is constrained to 400 m, but numerical simulations indicate that the maximum laser output power can be elevated to 113 mW by simply extending the length of the fiber and housing it in the same body. The tolerance to the solar tracking error was quantified, and the results demonstrated that more than 80% of the maximum output power can be sustained up to a ±23° tracking error. This study demonstrates the capability of the fully planar SPFL to operate without solar tracking.

Transversely solar-pumped fiber laser with parabolic trough

We studied transversely solar-pumped Nd3+ doped fiber laser with parabolic trough via simulation models developed by Monte Carlo photon tracing method. Our analysis involved estimating losses at cavity walls and the absorption efficiency within the fiber core. Factoring in the absorption distribution of pumped solar radiation in the fiber, we determined an absorption efficiency of 8% for a 287 meter long fiber arranged in a semicircular configuration. Subsequently, our calculations found a laser output of 3.03 W for this fiber laser system, resulting in an overall conversion efficiency of 4.29% from solar to laser beam.

Solar side-pumped Nd-doped fiber laser based on a doughnut-shaped hollow reflector

A high-power solar side-pumped Nd-doped fiber laser based on a doughnut-shaped hollow reflector (DHR) is proposed. The primary concentrator consists of twelve off-axis parabolic mirrors. The DHR coupled with an array of three-dimensional compound parabolic concentrators (3D-CPCs) functions as the secondary concentrator, inside which many cycles of Nd-doped fiber is coiled. After being reflected by the off-axis parabolic mirrors, the sunlight is launched into the DHR through the twelve 3D-CPCs, and experiences multiple-times reflection by the DHR, and finally is absorbed by the Nd-doped fiber for laser oscillation. Ray tracing shows that 173-W of solar power can be absorbed by the fiber. By solving the rate equations and power transmission equations, laser output power, slope efficiency and optical-to-optical conversion efficiency of 10.3 W, 6.12% and 5.94%, respectively, are realized. This kind of solar-pumped fiber laser thus offers a new route for achieving high-power solar-pumped laser sources.

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

We have developed a fully planar solar-pumped fiber laser using a solid-state luminescent solar collector (LSC). This laser does not use any focusing device, such as a lens or mirror; thus, it can lase without tracking the sun. Our developed device with an aperture of 30 cm emits 15 mW, corresponding to an optical-to-optical conversion efficiency of 0.023% and a collection efficiency of 0.21 W/m2. A 12-fold improvement over a previously developed liquid LSC is achieved by combining the total internal reflection of the solid-state LSC with dielectric multilayer mirrors. The observed laser power is in good agreement with that predicted via numerical simulation, demonstrating the effectiveness of our proposed method.

Волоконные лазеры с солнечной накачкой без первичного концентратора.

We studied solar pumped fiber lasers without primary concentrator. A model of solar sidepumped Nd3+ doped silica fiber lasers was developed using photon tracing method. Theabsorbed power distribution, possible losses and the pumping efficiency are estimated using the model. We analyzed the estimated paramters and drawed conclutions which have many suggests for improved design of solar pumped fiber lasers. The absorption efficiency of a fiber solar laser without a primary concentrator or sun tracker was calculated to be 0.2% for a 190 m fiber. The output power of the fiber laser is 40 mW, and the conversion efficiency from sunlight to laser light is calculated to be 0.06%. The developed model allows one to estimate the overall efficiency, output power and absorption distribution of Nd3+ fiber lasers without focusing optics, enabling various investigative comparisons.

Side-pumped solar Nd-doped fiber laser based on off-axis parabolic mirror array

In order to improve the output power of solar pumped fiber lasers, a new kind of transversely pumping configuration is proposed. The primary concentrator is an off-axis parabolic mirror array made up of ten fan-annular parabolic mirrors, and the secondary concentrator is a compound reflective concentrator composed of ten 3D compound parabolic concentrators (3D-CPCs) and a ring chamber. The collected sunlight passes through the 3D-CPCs’ inlet into the compound reflective concentrator which has a high reflecting film on the inner surface. An Nd-doped fiber is pumped when sunlight passes through the fiber core many times in the chamber. 490.8 W sunlight is absorbed by the fiber core according to ray tracing simulation. Based on solving the rate equation and the power transmission equation of the uniformly pumped solar fiber laser, 12.2 W laser output is obtained and the optical-to-optical conversion efficiency reaches 2.48 %. This solar concentrating system offers a new method to improve the output power of solar pumped fiber laser.

Monte Carlo simulation of a transversely excited solar-pumped fiber laser

A Monte Carlo ray-tracing simulation was developed for a transversely excited solar-pumped fiber laser without focusing optics. To make this possible, the fiber is immersed in a liquid sensitizer and sandwiched between highly reflective mirrors. The top reflector is dichroic to transmit solar radiation but reflect fluorescence to confine photons that match the absorption band of the active fiber. Simulation was used to evaluate the validity of the concept and optimize device performance. For comparison with the calculations, preliminary experiments were conducted by illuminating a 30 cm aperture, laser module with a solar simulator. The observed gains were in good agreement with the calculations for various conditions, such as sensitizer concentration and mirror reflectivity. Finally, we show that the predicted output power reaches 29 mW when the fiber length is optimized, and it will be enhanced to 150 mW with 0.21% solar-to-laser efficiency under the assumption of a reabsorption-free sensitizer.

Enhanced near-infrared emission in Yb3+-Cr3+ codoped KZnF3 glass ceramics excited by a solar simulator

Cr3+-Yb3+ codoped bulk glass-ceramics containing KZnF3 nanocrystals are fabricated by thermal treatment of cast glass samples and characterized by X-ray diffraction and transmission electron microscopy. The luminescent properties of the glass and glass ceramic are investigated from the measured photoluminescence spectra and fluorescent lifetime. The measurement results demonstrate that Cr3+ and Yb3+ ions are both predominantly hosted in the KZnF3 nanocrystals, and the energy absorbed by Cr3+ ions is efficiently transferred to Yb3+ ions when excited at 450 nm. Compared to the glass, the near-infrared emission in the Cr3+-Yb3+ codoped glass ceramics is significantly enhanced when the excitation wavelength lies in the range λ~400–800 nm of a solar simulator. Results indicate that the Cr3+-Yb3+ codoped KZnF3 glass ceramic provides a promising material for spectral conversion from visible sunlight to near-infrared emission and a novel gain material for solar pumped fiber laser.

Silicon photovoltaic cells coupled with solar-pumped fiber lasers emitting at 1064 nm

We have designed silicon (Si) photovoltaic (PV) cells coupled with solar-pumped fiber lasers (SPFLs), by considering the unique illumination conditions for PV cells: (1) monochromatic (1064 nm) and normal incidence, (2) large intensity, and (3) small area. We have revealed that a multilayered bandpass filter formed on the front surface of a PV cell equipped with a diffuse reflector on the back surface sufficiently traps the illumination. This, in turn, allows us to use a thin Si wafer to eliminate the detrimental effect of the series resistance in the cell under intense illumination, along with a small lateral size that is suitable for direct connection with an SPFL. Simulated conversion efficiency of the newly designed 20 μm-thick Si PV cell with the 14-layerd bandpass filter and Lambertian back reflector is 61% under normally incident 1064 nm illumination at 1 kW/cm2, which is twice as high as that of a conventional surface-textured Si solar cell of 75 μm in thickness.

Spectroscopic investigation of Nd3 + single doped and Eu3 +/Nd3 + co-doped phosphate glass for solar pumped lasers

We report on the fabrication and characterization of Nd3+ doped phosphate glass to be used as active laser medium for developing solar pumped fiber laser emitting at 1.06μm. Several Nd3+-doped phosphate glass samples were fabricated, with a host composition of (mol%) 65P2O5:17Li2O:3Al2O3:4B2O3:5BaO:6La2O3 and with a concentration of Nd3+ up to 10mol%. In order to exploit the unabsorbed solar energy by Nd3+ ions, Eu3+ co-doping of Nd3+-doped phosphate glasses was also investigated to asses a potential increase in the overall pump power conversion efficiency. Physical and thermal properties of single doped and co-doped samples were measured and their spectroscopic properties are discussed. The effect of Nd3+ doping concentration on emission spectra and lifetimes was investigated in single doped samples in order to study the concentration quenching effect on luminescence performance. The shape of the fluorescence spectrum did not change by increasing the Nd3+ doping level while the lifetime of the Nd3+:4F3/2 was found to decrease. The following characteristic value parameters were calculated: radiative lifetime τ0=367μs and quenching concentration N0=8.47 E+20ions/cm3.The Eu3+ co-doping was found to give a limited increase to the glass pump power absorption limited to the UV range. Although energy transfer from Eu3+ to Nd3+occured, a large Eu3+ concentration dependent quenching of Nd3+ fluorescence was observed. This latter process decreases the radiative quantum efficiency of Nd3+:4F3/2 emitting level and hence limits the attractiveness of Eu3+ sensitization for Nd3+ laser action.

Laser emission from a solar-pumped fiber

We report the realization of a solar-pumped fiber laser (SPFL) using a double-clad (a center core/ an inner clad working also as optical waveguide/ an outer clad) Nd-doped fluoride optical fiber as a laser medium. With a compact off-axis parabolic mirror of 5 cm in aperture diameter, the natural sunlight is concentrated by a factor 10⁴, and introduced partly into the core of the fiber and partly into the inner clad in which the light is guided in some distance and transferred to the core after all. We have obtained clear laser spectrum characteristics with approximately 0.01 nm full-width-half-maximum of the laser line at the peak wavelength of 1053.7 nm, a low-lasing threshold of 49.1 mW, a slope efficiency of 6.6%, and a total efficiency of 1.76%. Further optimization of the medium properties, optical cavity, and concentration technique will yield higher efficiency and lower threshold.

Spectroscopic properties of Er doped and Er, Nd codoped fluoride glasses under simulated sunlight illumination

We investigated the fluorescence characteristics of Er codoped Nd doped ZBLAN glasses proposed for solar pumped fiber laser (SPFL) under simulated sunlight. Er is used as a sensitizer because it absorbs a part of the ultraviolet and visible light where is no absorption of Nd. Under simulated sunlight illumination, Er singly doped fluoride glass displayed four emission bands with peaks at 550, 848, 977 and 1533 nm attributed to the 4S 3/2- 4I 15/2, 4S 3/2- 4I 13/2, 4I 11/2- 4I 15/2 and 4I 13/2- 4I 15/2 electronic transitions of Er, respectively. The quantum efficiency measurement was carried out using an integrating sphere and under the simulated sunlight excitation showed a maximum of 73% for 0.5 mol.% of ErF 3 in ZBLAN glass. In Nd, Er codoped fluoride glass, the 1.05 μm emission of Nd was observed under 380 nm excitation what supposes the energy transfer from Er to Nd in ZBLAN glasses as Nd has no absorption at the wavelength. Er, Nd codoped fluoride glasses are promising as a sensitized laser media for solar pumped fiber lasers.