Laser Technology
The Laser Technology Group at CEFITEC, founded and led by Professor Dawei Liang, was established to advance solar-pumped laser technology.
Research activities have focused on innovative solar-pumped laser configurations, particularly through the adoption of Ce:Nd:YAG as an active medium in recent years. The first solar laser emission from this material in 2020, followed by a 140% efficiency improvement in 2021, marked an important step in the group's research. Due to the enhanced overlap between the Ce:Nd:YAG absorption bands and the solar spectrum, compared with conventional Nd:YAG, this transition overcame long-standing efficiency bottlenecks, leading to five major breakthroughs over the last five years:
1. The first simultaneous solar laser emission from three Ce:Nd:YAG rods within a single pump cavity, achieving record collection and conversion efficiencies of 41.3 W/m² and 4.64%, respectively. This breakthrough was featured by Laser Focus World (2022).
2. Achieving the lowest reported pump threshold to date for Ce:Nd:YAG solar laser operation (16.5 W) and the highest solar-to-TEM00 mode laser conversion efficiency (2.06%).
3. Enhanced practical robustness of solar-pumped lasers through high-tolerance tracking error compensation.
4. The first simultaneous emission of three and four fundamental-mode solar laser beams, considerably improving total TEM00-mode laser output power stability and tracking error compensation capacity.
5. The publication of the world’s first English-language textbook on “Solar-Pumped Lasers” (Springer-Nature, 2023), bridging imaging/non-imaging solar concentrator theory and solid-state laser physics.
The group's research is supported by dedicated solar laser facilities at NOVA University Lisbon, including a solar heliostat, a solar tracker, a 1 kW solar furnace, several Fresnel lenses, and solar laser head prototypes. The group has also maintained a strong collaboration with the PROMES-CNRS institute in France since 2011 through ten EU SFERA I–III Transnational Access grants and two EU RISEnergy grants. More recently, its expertise has contributed to a UK–Portugal collaboration with Northumbria University on solar-pumped maser technologies, supported by the Royal Society in the United Kingdom.
Over the last two decades, the group's research has also been supported by more than €1.6 million in competitive FCT-MCTES funding dedicated to human resources. This investment has fostered researcher career progression, exemplified by the transition of group members from PhD training to CEECIND Junior Researcher positions and, more recently, an FCT-Tenure position. The group has mentored seven PhD students supported by FCT-MCTES fellowships and three PhD students funded through scholarships from the Algerian Ministry of Science.
Research developed within the group has been reported in more than 137 Scopus-indexed publications, complemented by editorial contributions to international journals. The group's work has been highlighted by international scientific journals and professional media, including Laser Focus World, SPIE News, and the Journal of Photonics for Energy. The group leader has also been recognized among the World's Top 2% most-cited scientists in the Stanford University–Elsevier ranking (2021, 2023–2025), further reflecting the international visibility and impact of the research carried out within the group.
Laboratory Facilities
The solar-pumped laser experiments are conducted in the CEFITEC solar laser laboratory at the NOVA FCT campus.
A two-axis heliostat equipped with plane solar mirrors is installed outside the laboratory to redirect incoming sunlight indoors. The mirrors are fabricated from 4 mm-thick low-iron glass substrates, providing approximately 93% reflectance of the incoming solar radiation.
A direct solar-tracking system is also integrated into the heliostat structure, supporting the primary concentrator (Fresnel lens) and the laser head while maintaining accurate solar alignment, thus enabling solar-pumped laser experiments to be performed directly outdoors as well.
The solar furnace in the solar laser laboratory consists of a parabolic mirror with a diameter of 1.5 m, a rim angle of 60°, and a focal length of 660 mm, serving as one of the primary concentrators of the solar-pumped laser systems. The parabolic mirror is coated with a back-surface silver reflective layer. Under typical clear-sky conditions, approximately 1 kW of solar power can be concentrated into an 8 mm full width at half maximum (FWHM) focal spot with a near-Gaussian intensity distribution.
The solar laser laboratory is equipped with several Fresnel lenses of different sizes and focal lengths, which serve as primary solar concentrators in various solar-pumped laser configurations.
The latest solar-pumped laser head prototypes developed by the Laser Technology Group can be found here.
Team
The Laser Technology Group currently comprises four integrated members:
• Dawei Liang – Associate Professor with Habilitation and Head of Research
• Joana Almeida – Assistant Professor (FCT-Tenure Funding)
• Cláudia R. Vistas – Junior Researcher (FCT Programmatic Funding)
• Bruno D. Tibúrcio – Junior Researcher (FCT CEEC Individual Funding)
Collaborations
The group has also maintained a strong collaboration with the PROMES-CNRS institute in France since 2011 through ten EU SFERA I–III Transnational Access grants and two EU RISEnergy grants.
More recently, its expertise has contributed to a UK–Portugal collaboration with Northumbria University on solar-pumped maser technologies, supported by the Royal Society in the United Kingdom.
