Researchers at Vilnius University have reported perovskite-based laser structures that held stable performance over more than 400 million pulses, in a study published in Advanced Optical Materials.
The paper, "Highly Stable Solution-Processed CsZnPbI3 Perovskite Distributed Feedback Lasers", is by Abdul Mannan Majeed and colleagues. Majeed is a doctoral student and junior researcher at the university. The work was described by Vilnius University and reported by Phys.org.
Perovskites are attractive largely because they are cheap and simple to make. "Perovskites are popular right now because they're easy to produce using casting methods," said Dr Patrik Ščajev, one of the Vilnius researchers.
They are also notoriously fragile. Perovskites degrade quickly in the presence of moisture: they draw water out of the air and then dissolve, because water alters their chemical properties.
The team spin-cast its perovskites in a nitrogen atmosphere, replaced part of the lead with zinc to reduce the lead content, and formed distributed-feedback gratings on the samples by interference laser ablation.
Samples were stored under a range of different conditions before being measured.
Measurement fell to Dr Augustas Vaitkevičius, who used high-resolution confocal microscopy and a multi-mode microscope with laser scanning, working on a spot roughly the width of a human hair. "It's a slow, painstaking process," he said. The analysis took several weeks.
The distributed-feedback samples showed good stability and a narrow emission line, and the team found a correlation between the onset of stimulated emission and improvements in luminescence intensity and emission wavelength. "That was exactly what we were aiming for," Ščajev said.
The figure that will travel is the 400 million. It is worth noticing what kind of figure it is.
The paper reports stability over more than 400 million pulses. That is a statement about how far the measurement got. It is not a statement about where the material gives up, because the material did not.
This makes it the strongest available result and simultaneously the least informative one. A compound that dissolves in ordinary air has been certified stable up to the point at which somebody in Vilnius stopped counting, and the certificate therefore records that person's endurance rather than the laser's.
Our analysts propose a revised figure accordingly. The Vilnius structures are stable for 400 million pulses, plus however many more they would have survived had the confocal microscope been attended for a further several weeks. The Department of Unnecessary Research has no view on the laser. It would like to know who was watching.