Solar-pumped Laser Research Articles

Solar pumped Nd:YAG laser efficiency enhancement using Cr:LiCAF frequency down-shifter

The possibility of increase of Nd:YAG solar pumped lasers pumping efficiency with the use of Cr:LiCAF as a solar spectrum frequency-down-shifting element is studied by the simulation calculation method. Comparative analyses of side- and end-pumping schemes are conducted. The numerical experiments have been conducted for combinations of Nd:YAG active medium and Cr:LiCAF for both side- and end-pumping configurations. It is shown that the use of Cr:LiCAF frequency down-shifter significantly increases the pumping efficiency of Nd:YAG active medium in both cases. In addition the replacement of Nd:YAG with cerium co-doped Nd:YAG have shown possibility of further increase the efficiency.

太阳光泵浦固体激光阈值的理论分析

太阳光泵浦固体激光阈值的理论分析

Enhancing of solar pumped liquid laser efficiency

The neodymium-containing phosphorus oxychloride liquid laser material is studied as an active medium for pumping by concentrated solar radiation at the focus of small-size parabolic-dish concentrators. The possibility of increase its efficiency by means of frequency-down-shifting elements of solar spectrum is examined by simulation calculations by Monte-Carlo and ray-tracing methods using. More than 40% efficiency increase is obtained.

A new approach in solar-to-laser power conversion based on the use of external solar spectrum frequency converters

A new approach based on the use of external frequency converters for Nd:YAG solar pumped lasers providing effective conversion of solar-to-laser power is proposed. The possibility of a more than four-fold increase in Nd:YAG solar pumped laser efficiency is shown by the simulation calculation method.

Solar-pumped TEM00 mode laser simple design with a grooved Nd:YAG rod

A simple high-brightness TEM00 mode solar laser design with a grooved Nd:YAG rod pumped through a heliostat–parabolic mirror system is proposed here. A fused silica semi-cylindrical lens was combined with a 2V-shaped pumping cavity to provide efficient side-pumping along the grooved 1.0at.% Nd:YAG rod. Optimum pumping and laser beam parameters were found through ZEMAX and LASCAD numerical analysis. The proposed scheme offered a circularly symmetric and uniform absorption profile. Maximum TEM00 mode solar laser power of 25.5W was numerically achieved with a 3.5mm diameter grooved rod, corresponding to 8.5W/m2 collection efficiency. 17.1W laser beam brightness figure of merit was attained, being 4.3 times more than the previous record with TEM00 mode Nd:YAG solar laser, and 10,000 times higher than last year’s result with a large grooved Nd:YAG rod. To validate the proposed pumping scheme, a solar laser prototype was built and firstly tested with a small-scale heliostat–parabolic mirror system of Universidade NOVA de Lisboa, producing 4.0W continuous-wave TEM00 mode solar laser power at 3.6W/m2 collection efficiency and 3.0W laser beam figure of merit.

High-efficiency solar-pumped TEM00-mode Nd:YAG laser

Here we report a significant progress in solar-pumped laser slope efficiency and collection efficiency by pumping a 4.0mm diameter grooved Nd:YAG single-crystal rod with a heliostat–parabolic mirror solar energy concentration system. The incoming solar radiation is firstly collected and focused by the system. An ellipsoid-shaped fused silica concentrator is then used to further compress the concentrated solar radiation into the grooved rod within a 2V-shaped pumping cavity. 4.5W continuous-wave TEM00-mode (M2≤1.1) 1064nm solar laser power is finally measured, attaining 2.36% laser slope efficiency, which is 3.37 and 2.91 times higher than previous records by Fresnel lens and parabolic mirror respectively. Record-high TEM00-mode solar laser collection efficiency of 4.0W/m2 is also achieved.

Simulation model of a new solar laser system of Fresnel lens according to real observed solar radiation data in Helwan of Egypt

A new simulation model of a new solar pumped laser system was tested to be run in Helwan in Egypt (latitude φ=29°52′N, longitude λ=31°21′E and elevation=141m) as an example of an industrial polluted area. The system is based on concentrating the solar radiation using a Fresnel lens on a laser head fixed on a mount tracking the sun during the day and powered by a DC battery. Two cases of this model are tested; the first one is the model consisting of a Fresnel lens and a two-dimensional Compound Parabolic Concentrator (CPC), while the other is the model consisting of a Fresnel lens and a three-dimensional Compound Parabolic Concentrator (CPC). The model is fed by real actual solar radiation data taken in Helwan Solar Radiation Station at NRIAG in the various seasons in order to know the laser power got from such a system in those conditions. For the system of Fresnel lens and 2D-CPC, an average laser output power of 1.27W in Winter, 2W in Spring, 5W in Summer and 4.68W in Autumn respectively can be obtained. Accordingly, the annual average output power for this system is 3.24W. For the system of Fresnel lens and 3D-CPC, an average laser output power of 3.28W in Winter, 3.55W in Spring, 7.56W in Summer and 7.13W in Autumn respectively can be obtained. Accordingly, the annual average output power for this system is 5.38W.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer.

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd3+-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm−2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.

Energy transfer from Cr to Nd in substitutional crystal Y3GaxAl5−xO12 codoped with Nd and Cr

Garnet crystals codoped with Nd3+ and Cr3+ ions are a candidate for solar-pumped laser materials. Substitutional disordered crystals Y3GaxAl5−xO12 were prepared to improve the pumping efficiency of Nd3+ luminescence and energy transfer from Cr3+ to Nd3+ ions. The substitutional disordered crystal host produced inhomogeneous broadening of the Nd3+ and Cr3+ optical spectra. Enhancement of overlapping between the Cr3+ absorption bands and the solar spectrum, and between the Cr3+ luminescence bands and the Nd3+ absorption lines led to the increases of the pumping efficiency and the energy transfer rates, respectively. The excitation spectrum of the Nd3+ luminescence, the nonexponential decay curves of the Cr3+ luminescence, and the quantum yields of the Cr3+ and Nd3+ luminescence have given evidence on the energy transfer from Cr3+ to Nd3+ ions.

Consideration of coordinated solar tracking of an array of compact solar-pumped lasers combined with photovoltaic cells for electricity generation

A monochromatic laser light with a photon energy just above the band edge of photovoltaic cells can be converted into electricity with minimal thermal loss. To attain efficient conversion of sunlight to laser light, a coordinated solar tracking system for an array of originally designed compact solar-pumped lasers of 50 mm aperture diameter is being constructed. As for the feasibility of this system, a prototype with a holding capacity of 25 compact solar-pumped lasers has been fabricated. The primary requisite of this system is that the angular accuracy of tracking should be below 1 mrad for all 25 compact solar-pumped lasers to sustain their continuous lasing. To realize this, imperative challenges have been elucidated including thermal expansion under sunlight. A prototype fabricated with its main frame made of Super Invar alloy was found to fulfill the requisite by measurement using a three-dimensional coordinate measuring machine.

Light trapping for silicon photovoltaic cells illuminated by solar-pumped lasersemitting at 1064 nm

We have demonstrated a significant light-trapping effect for a silicon photovoltaic cell using a bandpass filter on the front surface and a diffuse reflector on the back surface, which is coupled with a solar-pumped laser emitting at 1064 nm, as a new approach to highly efficient solar photovoltaics. We carried out Monte-Carlo simulation of the light-trapping process to consider the effects of realistic optical properties of the surface treatments, and clarified the requisites to remarkably improve the absorbance of the cell. A multilayer bandpass filter consisting of TiO2 and SiO2 was employed, in which the thickness of each layer was optimized. A Si surface roughened by acid etching and covered with a Ag layer realized sufficient diffuse reflection properties. The prototype for optical evaluations using a 45-µm-thick Si wafer, which is extremely thin compared with conventional silicon solar cells, almost perfectly absorbed the monochromatic incident light even though the wavelength was very close to the absorption edge.

Emission sensitization processes involving Nd3+ in YAG

The paper investigates the characteristics of sensitization processes of Nd3+ emission in YAG ceramics under broad band pumping by co-doping with Cr3+ and the prospect of using Nd3+ and Cr3+ for sensitization of emission of Yb3+. It is evidenced that the energy transfer from Cr3+ to Nd3+ involves both direct and weak migration-assisted processes and is thus dependent on the concentrations of both species. It is also found that the ion–ion interaction responsible for the direct transfer contains besides the dipole–dipole coupling strong superexchange contribution that dominates the transfer to the Nd3+ ions up to the third coordination sphere and has major implication in sensitization. Investigation of (Cr, Nd, Yb)-doped YAG ceramics shows that Cr3+ can sensitize the emission of Yb3+ both via the chain Cr–Nd–Yb or by direct Cr–Yb energy transfer. The prospect of utilization of these processes in the solar-pumped laser is discussed.

Energy transfer efficiency from Cr(3+) to Nd(3+) in solar-pumped laser using transparent Nd/Cr:Y(3)Al(5)O(12) ceramics.

We report energy transfer efficiency from Cr3+ to Nd3+ in Nd (1.0 at.%)/Cr (0.4 at.%) co-doped Y3Al5O12 (YAG) transparent ceramics in the laser oscillation states. The laser oscillation has performed using two pumping lasers operating at 808 nm and 561 nm; the former pumps Nd3+ directly to create the 1064 nm laser oscillation, whereas the latter assists the performance via Cr3+ absorption and sequential energy transfer to Nd3+. From the laser output power properties and laser mode analysis, the energy transfer efficiency was determined to be around 65%, which is close to that obtained from the spontaneous Nd3+ emission.

Design of a solar-pumped semiconductor laser

Since their first demonstration in 1962, solar-powered lasers have attracted interest as a tool for generating and distributing renewable energy. Proposals have ranged from orbiting solar laser power stations beaming energy down to terrestrial photovoltaic receivers, to arrays of solar lasers in desert areas linked to population centers via optical fibers. However, despite several decades of research, solar-powered lasers have yet to reach the levels of efficiency or output beam quality that would make these applications feasible. Here we propose a new solar laser architecture, the solar-pumped vertical external cavity surface emitting laser (SP-VECSEL), as a logical continuation of the proven mode-converting capabilities of diode-pumped VECSELs. In experiments using VECSEL gain samples pumped using sunlight, we demonstrate that no major drop in efficiency is observed beyond that associated with the quantum defect of the pump light, allowing us to predict that SP-VECSEL performance can substantially surpass that of existing solar lasers.

Solar photovoltaics via photoelectric conversion, specialized for monochromatic light produced by solar-pumped lasers

Solar photovoltaics via photoelectric conversion, specialized for monochromatic light produced by solar-pumped lasers

太陽光励起レーザー開発とその応用

太陽光励起レーザー開発とその応用

Solar-pumped TEM00 mode Nd:YAG laser by a heliostat—Parabolic mirror system

Here we report a significant advance in solar-pumped laser beam brightness by pumping a 3mm diameter Nd:YAG single-crystal rod with a heliostat-parabolic mirror system. The incoming solar radiation is first collected and focused by the system. A rectangular fused silica light guide and a 2D-CPC concentrator are then combined to further compress the concentrated solar radiation into the laser rod within a V-shaped pumping cavity. 4.4W continuous-wave TEM00 mode (M2≤1.05) 1064nm solar laser power is finally produced, attaining 4.0W laser beam brightness figure of merit, which is 2.1 times higher than the previous record by a Fresnel lens. 0.81% TEM00 mode laser slope efficiency is achieved.

Recyclable Metal Air Fuel Cells Using Sintered Magnesium Paste with Reduced Mg Nanoparticles by High-Repetitive Ns Pulse Laser Ablation in Liquid

An energy cycle using solar power and metals has been proposed. High repetitive laser pulses are generated by a solar-pumped laser or a laser generated using solar power, and the laser pulses are irradiated to metal oxides in liquid. We can obtain reduced metal nanoparticles with this method, and solar power is effectively stored as chemical energy. We succeeded in producing sintered Mg metal paste. The sintered Mg nanopaste reduced Mg nanoparticles from pure MgO or Mg(OH)2 powder, collected from used Mg air cells, by laser ablation in liquid using a high-repetitive ns pulse Nd:YAG laser. We also fabricated metal air fuel cells using sintered Mg plates as negative electrodes. Electricity was successfully produced from these cells. A light-emitting diode and a motor were connected to the Mg paste air fuel cells and the output voltage and current of the cells were measured. The observed output voltage was 1.4 V when they were connected to a low load, which is the same as conventional Mg air cells. Metal oxides were reduced with high efficiency and at a noticeably low cost by using lasers generated from solar energy. This makes it possible to recycle Mg plates. The new recyclable Mg paste air fuel cells are expected to become common power supplies with high-energy density and high output power.

Design of TEM00 mode side-pumped Nd:YAG solar laser

An alternative solar laser pumping approach is here proposed to improve substantially TEM00 mode solar laser power. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a laser head by four plane folding mirrors. A secondary concentrator with four semi-cylindrical fused silica lenses is designed to compress the highly concentrated solar radiation to a Nd:YAG single-crystal rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAX© and LASCAD© numerical analysis. The proposed design offers a uniform absorbed pump distribution along the laser rod which has a minimum in its central region, reducing considerably thermal lensing effects. High order mode laser power of 83W is numerically attained with a short symmetric laser resonant cavity, leading to high collection efficiency of 20.8W/m2 for side-pumped Nd:YAG solar laser. Large spatial overlap between the pumped volume and the fundamental mode volume is found for an asymmetric laser resonator with concave end mirrors of large radius of curvature. 47.4W TEM00 laser output power is numerically achieved, leading to a solar laser beam brightness figure of merit of 32W. This value is 16.8 times more than the previous record for solar-pumped laser.

A Novelty Analysis Method of Solar-Pumped Laser with Fresnel Lens and Cr/Nd:YAG Ceramic

In this paper, the simple and effective experimental method is proposed for studying on the influence of tracing deviation on solar-pumped laser output performance. The threshold pumping power is obtained by the novelty method. The experimental setup of solar-pumped laser employed Fresnel lens of 1.4×1.05m2 and diffuse reflective conical cavity focusing solar radiation on the size of 5mm×60mm Cr/Nd:YAG ceramic. The effective threshold pumping power calculated is 190W, which is about 30% lower than reported results.