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New Solar-Pumped Lasers Enhance Solar-to-Laser Conversion Efficiency

The development of effective solar cells, which use sunlight to create electricity or hydrogen by splitting water, has attracted a lot of interest worldwide. Utilizing solar energy as a laser pumping system is an additional method of capturing plentiful, cost-free solar energy.

Simplified scheme of a side-pumped solar laser system with four off-axis parabolic mirrors: (left) front view and (right) side view; (inset) laser head is mounted at the common center point of the four off-axis parabolic mirrors. Image Credit: Boutaka, Liang, and Abdelhamid Kellou

Deep space communication, atmospheric sensing, high-temperature material processing, and hydrogen synthesis are a few uses for high-power lasers. However, they frequently cost a lot of money and have performance issues brought on by thermal stress.

Scientists from Portugal and Algeria have published a study in the SPIE Journal of Photonics for Energy that describes a novel solar-powered laser system that satisfactorily resolves these problems. Contrary to those pumped with traditional sources, this laser has a higher laser conversion efficiency (such as flash lamps and LEDs).

The approach we adopted in this study allowed us to develop a powerful solar-powered laser operating in TEM00 mode, the fundamental or lowest-order mode. Each of these modes (our laser sustains multiple fundamental modes) can be precisely controlled with minimal heat input to the pump cavity. This enables us to tailor the applied energy to the specific needs of an application.

Dawei Liang, Study Corresponding Author and Associate Professor, Universidade Nova de Lisboa

To improve the design characteristics of a TEM00-mode Nd:YAG solar laser beam, the scientists used numerical simulations. They also used four big off-axis parabolic mirrors with a combined collection point of 10 m2, four 2V-shaped pump chambers, and four laser rods to fill them with sunlight.

The laser head in our design also includes four secondary fused-silica aspheric concentrators, and four rectangular fused-silica light guides. This ensures an even distribution of the absorbed pump power within each rod and helps avoid heating damage resulting from thermal lensing and thermal stresses occurring in conventional single rod solar lasers.

Dawei Liang, Study Corresponding Author and Associate Professor, Universidade Nova de Lisboa

The solar laser performed better due to this. According to the numerical estimates, the TEM00 mode’s total laser power is 155.29 W. In contrast to previous designs with a similar arrangement, this led to a two-fold increase in the collecting performance and a 1.24-fold gain in the conversion efficiency.

Space-based solar power generation is one of the design’s key potential applications. This entails gathering solar energy in orbit, transforming it into a laser beam, and beaming it back to Earth so that it can be used to power solar cells. This process is more reliable and needs less transmission and receiving equipment than microwave power transmission as it is not affected by the Earth’s atmosphere.

Despite having a higher sun-to-laser conversion efficiency than a solar laser, Liang points out that photovoltaic-powered diode-pumped lasers are far less appropriate for long-term space applications.

This is due to a diode-pumped laser’s constrained lifetime of the diode pump source and its more intricate laser system. 

Ultimately, this study provides a clear design for highly efficient, space-ready solar lasers, illuminating a path to elevating solar-powered lasers to new heights.

Journal Reference

Boutaka, R., et al. (2022) Efficient TEM00-mode solar laser using four Nd:YAG rods/four off-axis parabolic mirrors pumping approach. SPIE Journal of Photonics for Energy.

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