Doctorate in Applied and Engineering Physics  

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Thesis Proposal for the

Doctorate Program in Applied and Engineering Physics (DAEPHYS)

Starting in the Academic Year 2016/2017

Proposal 016

Title:500W-class visible solar-pumped alexandrite lasers for aluminium welding applications.
Objectives (recommended length: 2000-3000 char):
The conversion of sunlight into laser light by direct solar pumping is of ever-increasing importance because free broadband sunlight is converted into laser light, which can be a source of narrowband, collimated, rapidly pulsed, tunable radiations with the possibility of obtaining extremely high brightness and intensity. Solar pumping offers extraordinary simplicity for space applications due to the complete elimination of electrical power generation and power conditioning equipments. Back to the Earth, alexandrite laser-based applications are emerging in the fields of laser machining, spectroscopy and LIDAR. Diode-pumped Nd:YAG lasers at 1064nm are well established systems but offer no tunability, and even with their harmonics (532nm/355nm), it entirely miss whole wavelength regions. Tunable Ti-sapphire laser usually requires complex laser pump sources that lead to high complexity and poor overall system efficiency. A significant weakness of visible laser diode array is its low power level of less than 100W, and performance degradation over time. Therefore, today´s diode-pumped alexandrite laser power level is limited to 26.1W. Thus, numerous applications can certainly be expected with powerful renewably pumped visible alexandrite laser by tuning its high-energy photon wavelength to better match the absorption spectrum of the targeted materials.
500W-class solar-powered alexandrite laser offers several advantages over CO2 and Nd:YAG lasers, which are perhaps the most used in laser welding applications. The wavelength of the alexandrite laser, at 755 nm, corresponds to a higher absorptivity in aluminium than the longer wavelengths of Nd:YAG and CO2 lasers. Powered with free solar energy, another attractive feature of the our proposal resides in the significant reduction in the operating cost, like the frequent replacement of laser lamps, expensive laser diodes stacks and, not less importantly, huge electricity consumption by classical lasers. The first green model for aluminium industry can be established.
Entirely avoiding visible semiconductor laser arrays or arc lamps by direct solar pumping
alexandrite lasers exhibits very promising potential to surmount the current laser aluminum welding efficiency limitations of many industrial laser such as Nd:YAG and CO2, enabling the most reliable, tunable, high-power visible laser operation over a multitude of years. 500W-class continuous-wave alexandrite laser power from 10 m2 Fresnel collection area with 5.0 % solar-to-laser efficiency, emitting at tunable 700-860nm wavelength, will constitute a ground-breaking solution to imminent industrial challenges.
Simplicity, short wavelength and its tunability, high power level, high overall efficiency, high beam brightness, low cost, and easy scalability are also most distinguished features of our proposal. The 500W-class laser will gradually establish itself as a technological leader through the joined collaboration and orientation efforts of both NOVA and ISQ.
Framework (recommended length: 500-2000 char):
1. Coordinator of H2020 FETOPEN-2016-2017-RIA, 737206 SoLVisible Proposal

“Kilowatt-class visible solar-pumped alexandrite lasers for space and terrestrial applications”
Research proposal was submitted on May, 11, 2016 by Universidade Nova de Lisboa ( Dawei Liang as the project coordinator), Imperial College London, SBP Sonne GmbH, University of Strathclyde, PROMES-CNRS and Euronovia. This proposal is the largely improved version of our previous SOLALEX proposal with encouraging above threshold score of 3.9, (4.0 for Excellence, 4.0 for Implementation and 3.5 for Impact, the final funding score was 4.5, 1.4 % success rate).
2. Partner of H2020-MSCA-RISE-2016 734625, SPLATech Proposal
“A Novel Solar-Powered Lasers-Advancement Technique”, Research proposal was submitted on April, 28, 2016 by PROMES-CNRS, Universidade Nova de Lisboa (Dawei Liang as a main partner responsible for high-concentration solar laser technologies) and Ion-Plasma Laser Technology Rsearch Institute of Uzbekistan

3. Coordinator of “New frontier in high-temperature solar furnace for application to renewable Mg recovery fromMgO” project
(PTDC/FIS/122420/2010, 2012-2015)

4. Coordinator of “High efficiency Cr:Nd:YAG solar laser for sustainable magnesium-hydrogen energy Cycle” project
(PTDC/FIS/103599/2008, 2010-2013),with the following evaluation results by FCT-MCTES

5. "Laser system with beam-shaping capacity for materials processing", QREN, project nº 30179, 2013-2015 ISQ

6. "High efficient and beam quality laser for the microprocessing of materials", QREN, projecto nº 11459, 2010-2012 ISQ
Tasks (recommended length: 1000-3000 char):
1. ZEMAX and LSCAD numerical analysis and optimization of the 500W-class solar-powered alexandrite laser in NOVA

2.500W-class solar-pumped continuous-wave 755nm alexandrite laser with optimized parameters will be designed and built in NOVA.

3. Experimental optimization of the 500W-class laser output performances, including the laser input-output characterization, laser slope efficiency, laser beam profile measurement in NOVA

3.100W-class TEM00 mode CW 755nm solar laser power will be another research highlight. Asymmetric laser resonant cavity will play an important role in achieving world-class fundamental-mode visible laser power in NOVA.

4. Both Q-switch and wavelength tunable devices will be integrated to this novel alexandrite laser by NOVA. Pulsed laser operation will be essential to achieve efficient key-hole welding of aluminium at 755nm wavelength

5. For comparing the welding performances and efficiencies, aluminium welding experiments by the 500W-class laser, other laser sources and conventional TIGs method will finally be carried out in both NOVA and ISQ.
Research centre/lab or R&D unit hosting the thesis project:
University to which the thesis project will be presented:
UNL - Universidade Nova de Lisboa
DAEPHYS Scientific Domain in which the project fits:
Optical technology
Relation of the project to the Scientific Domains of DAEPHYS:
Renewable solar-powered alexandrite laser technology fit well within the domain of Optical Technology
Candidate profile:
Good knowledge of optics and ZEMAX software is also perfered
Does this proposal involve more than one University?:
Synergies between the two Universities participating in the proposal:
DAEPHYS strongly encourages the presentation of thesis projects in co-supervision by researchers from two of the universities participating in the Program. In this field, explain the benefits resulting from the proposed co-supervision and the involvement of elements from the two universities, e.g. building critical mass teams, profiting from existing infrastructures or advanced equipments, profiting from expert technical know-how, etc. If the proposal involves only one University, write n/a.
(recommended length: 500-1000 char)
Does this proposal involve a company?:
Proposals involving a company:
DAEPHYS strongly encourages the presentation of thesis projects involving a company, preferably a high-tech company. These proposals have to: 1) be centered on a technological problem in which the partner company has been (or plan / would like to be) involved; 2) have a co-supervisor on the enterprise; 3) include part of the project to be carried out in the company.
(recommended length: 500-1000 char)
: This proposal is based a joined orientation efforts from both NOVA and ISQ (Instituto de Soldadura e Qualidade).
Beakthrough in aluminium welding efficiency is expected by the proposed high-power, high-efficiency solar-pwered alexandrite laser at 755nm, a very suitable wavelength for the effective absorption by aluminum material.
Comparative studies with the 500W-class alexandrite laser, other classical lasers and conventional TIGs be will be carried out both in NOVA and ISQ. Student will gain profound knowledges in both laser engineering from NOVA and laser material processing from ISQ.



Name:Dawei Liang
Institution:Universidade Nova de Lisboa
link to CV or indication of ORCID ID:



Name:Paulo Jorge Morais
Institution:Instituto de Soldadura e Qualidade
link to CV or indication of ORCID ID:


Uploaded PDF document: proposal-016.pdf