Joana Almeida

Junior Researcher

242 - Ed. I


Research Areas

Solar-pumped Lasers

Solar energy transmission and concentration

PhD Thesis: "Advances in solar-pumped laser efficiency and brightness"

PhD Degree in Physics Engineering

Adviser: Prof. Doutor Dawei Liang

Advances in both solar-pumped laser efficiency and brightness are herein presented. Several solar laser prototypes with both end-side-pumping and side-pumping configurations were studied and developed to efficiently pump small diameter Nd:YAG laser rods, leading to substantial increase in solar laser collection efficiency and brightness, which have gained international recognitions. All the design parameters were optimized in ZEMAX© non-sequential ray-tracing software. LASCAD© laser cavity analysis software was then used to optimize the laser resonator parameters. Based on the numerically optimization of the solar laser system, the solar laser prototypes were designed and built in Lisbon. Solar energy collection and concentration were achieved through the PROMES-CNRS heliostat-parabolic system, NOVA Fresnel lens system, and the recently new NOVA heliostat-parabolic system. Measurements of the solar input / laser output performance, beam quality M2 factors, and laser beam profiles for both multimode and fundamental mode regime were performed and compared with that of the numerical results. 13.9 W/m2 solar laser collection efficiency was achieved in 2013, through PROMES heliostatparabolic mirror system, by end-side-pumping a 5 mm diameter, 25 mm length Nd:YAG laser rod. This result was further increased to 21.1 W/m2, in 2015, within the same solar facility. In 2016, 25 W/m2 collection efficiency was reported, by end-side-pumping a thinner laser rod through NOVA heliostat-parabolic mirror system. In addition to the enhancement of solar laser collection efficiency, the thermal performance of end-side-pumped solar laser was also substantially improved. In 2017, record solar laser collection efficiency of 31.5 W/m2 was reported by end-sidepumping a 4 mm diameter, 35 mm length Nd:YAG laser rod in PROMES-CNRS heliostatparabolic mirror system. Also, record slope efficiency of 8.9% was achieved. A substantial progress in solar laser beam brightness with Fresnel lens was reported in 2013, through the first TEM00-mode solar laser. 1.9 W solar laser brightness was registered, being 6.6 times more than the previous record. The adoption of an asymmetric laser resonator, for maximum extraction of TEM00-mode solar laser, was also essential for improving significantly the solar laser brightness. By side-pumping a 3 mm diameter, 30 mm length Nd:YAG rod with a double-stage rectangular light guide / 2D-CPC concentrator, 4.0 W solar laser brightness was reported in 2015, doubling the previous record with Fresnel lens. TEM00-mode solar laser collection efficiency of 4.0 W/m2 was obtained by side-pumping a Nd:YAG grooved rod in 2016. Most recently, by endside-pumping a 4 mm diameter, 35 mm length, Nd:YAG rod, the TEM00 mode solar laser collection efficiency was almost doubled, reaching 7.9 W/m2. Record-high solar laser brightness of 6.5 W was also achieved. Advances in solar laser beam stability were also achieved by developing sculptured twisted light guides for efficient uniform redistribution of pump light into a thin and long laser rod. In addition to this, we were also able to demonstrate the first emission of doughnut shaped solar laser beam, which may widen the applications areas of solar-pumped lasers. The research efforts performed during this work for enhancing both solar laser efficiency and beam brightness are explained. Experimental results are discussed and future suggestions are proposed.

Main publications

J. Almeida, D. Liang, B. D. Tibúrcio, D. Garcia and C. R. Vistas,  Numerical modeling of a four-rod pumping scheme for improving TEM00-mode solar laser performance, Journal of Photonics for Energy 9, 018001 (2019).

D. Liang, C. R. Vistas, B. D. Tibúrcio and J. Almeida, Solar-pumped Cr:Nd:YAG ceramic laser with 6.7% slope efficiency. Solar Energy Materials & Solar Cells 185, 75-79 (2018).

J. Almeida, D. Liang, and C.R. Vistas, A doughnut-shaped Nd:YAG solar laser beam, Opt. Laser Technol. 106, 1-6 (2018). DOI: 10.1016/j.optlastec.2018.03.029 

D. Liang, J. Almeida, C.R. Vistas, and E. Guillot. Solar-pumped NdYAG laser with 31.5 W/m2 multimode and 7.9 W/m2 TEM00-mode collection efficiencies. Sol. Energ. Mater. Sol. Cells 159, 435-439 (2017). DOI: 10.1016/j.solmat.2016.09.048

J. Almeida, D. Liang, C.R. Vistas, R. Bouadjemine and E. Guillot, 5.5 W continuous-wave TEM00-mode Nd:YAG solar laser by a light guide / 2V pump cavityAppl. Phys. B - Lasers and Optics 121, 473-482 (2015). DOI: 10.1007/s00340-015-6257-z

J. Almeida, D. Liang, C.R. Vistas and E. Guillot , Highly efficient end-side-pumped Nd:YAG solar laser by a heliostat-parabolic mirror system, Appl. Opt. 54, 1970-1977 (2015).DOI: 10.1364/AO.54.001970

J. Almeida, D. Liang, E. Guillot and Y. Hadi, A 40W cw Nd:YAG solar laser pumped through a heliostat: a parabolic mirror system, Laser Phys. 23, 065801 (2013).DOI:10.1088/1054-660X/23/6/065801