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|As Contributors:||Alberto Amo · Dmitry Solnyshkov|
|Submitted by:||Amo, Alberto|
|Submitted to:||SciPost Physics|
|Domain(s):||Exp. & Theor.|
|Subject area:||Atomic, Molecular and Optical Physics - Experiment|
We report polariton lasing in localised gap states in a honeycomb lattice of coupled micropillars. Localisation of the modes is induced by the optical potential created by the excitation beam, requiring no additional engineering of the otherwise homogeneous polariton lattice. The spatial shape of the gap states arises from the interplay of the orbital angular momentum eigenmodes of the cylindrical potential created by the excitation beam and the hexagonal symmetry of the underlying lattice. Our results open interesting perspectives in view of studying nonlinear structures such as vortex solitons if a high number of particles is considered.
1. The paper demonstrates an interesting effect (fig.1) which is the emergence of a localised gap state in a honeycomb lattice of coupled micropillars
1. The emergence of the localised gap state is an interesting and plausible interpretation of the data; nevertheless, focussing 10's of mW onto such a small microstructure inevitably leads to heating and the generation of free carriers. I note the authors have excluded thermo-optic effects by modulating with 1e-6 duty cycle, but how about simple electro-optic effects?
2. The authors claim lasing in the title and throughout the paper. Unfortunatley, the evidence for lasing is very poor. There is still a lot of debate in the community of how to define lasing in such microlasers; the Nature Photonics list is a good start, but the real evidence would be to demonstrate coherence, e.g. via a g2 measurement. In the absence of such a measurement, the minimum they would need to show is a reduction in linewidth by a factor 2 as stipulated by the Shawlow-Townes equation.
3. The authors motivate the paper by stating that the study of 2D materials via "photonic lattice simulators can provide insights in their properties". It would be nice if these insights were better articulated in the conclusion. Instead, they refer to vortex solitons, and it is not particularly clear why these are interesting.
The explanations offered are plausible but need to be better supported by data (cf lasing claim) and the exclusion of conventional effects. Given that there have been many reports of laser, or laser-like action, in a large variety of III-V microstructures, the authors also need to articulate the significance of their findings better.
If the authors can address my three points convincingly, the paper could be considered for publication.