Should we strive to follow Nature’s checklist on how to claim lasing?
Other conference contribution, 2018
Concerns have been raised by the laser community that sufficient evidence to support a claim of lasing, in particular in high-b cavities, is not always provided in manuscripts sent in for peer-review or even in published journal papers. Therefore, Nature Photonics compiled and launched a checklist for manuscripts with a claim of lasing, about a year ago.1 Authors are asked to complete it prior to peer-review, and the checklist will be published with the paper as supplementary information. Is this checklist really necessary, and if so, is it complete?
To answer the first question, we have checked which of the points in the checklist that have been addressed in papers published on electrically injected GaN-VCSELs. The scrutinized papers are from eight different groups claiming lasing, and all except two were published before Nature’s checklist. Table 1 shows the summary; none of the papers addresses all points, most papers only address a few, and one does not provide evidence for any point.
Table. 1. Checklist fulfillment by GaN-VCSEL papers
Proving lasing in novel devices and materials can be very hard, in particular in high-β emitters. It is thus challenging to provide input to all the points in the checklist. Assuming the checklist can be completed, is it enough? Interestingly, a cavity-enhanced LED could tick almost all the boxes in the laser checklist, while a thresholdless laser would per definition not satisfy box 1. We therefore claim that determining the change in photon statistics from thermal light below threshold to coherent light above threshold via second-order photon autocorrelation measurements is crucial. This method has largely been ignored by the applied laser community, but is regularly used by the quantum optics community to study photon statistics of emission. Its importance to provide the means to distinguish between a cavity-enhanced LED and a laser is illustrated in Fig. 1.2 The intensity and linewidth dependence on excitation power are very similar for the two devices B and C. However, the equal-time second-order photon autocorrelation function, g(2)(0), is notably different with a clear reduction from 2 to 1 for the laser, i.e. showing a transition from spontaneous to coherent emission.
In summary, we think the laser checklist is much needed and a good initiative by Nature Photonics, that hopefully will improve the quality of published papers, improve the repeatability of results and allow for a better comparison of devices. Even though it may not always be feasible to provide answers to all the questions in the checklist, we should do our best in providing the strongest evidence possible - including excitation power dependent g(2)(0) measurements for high-b lasers - for our claims.
Fig. 1 Performance characteristics for an LED (A), a cavity-enhanced LED (B) and a high-b microlaser (C) in terms of a) optical output intensity, b) linewidth and c) second-order photon autocorrelation as a function of pump power, and intracvity photon number, respectively.
References
[1] https://www.nature.com/authors/policies/laserchecklist.pdf
[2] S. Kreinberg et al., Light: Science & Applications, 6, e17030, (2017).
To answer the first question, we have checked which of the points in the checklist that have been addressed in papers published on electrically injected GaN-VCSELs. The scrutinized papers are from eight different groups claiming lasing, and all except two were published before Nature’s checklist. Table 1 shows the summary; none of the papers addresses all points, most papers only address a few, and one does not provide evidence for any point.
Table. 1. Checklist fulfillment by GaN-VCSEL papers
Proving lasing in novel devices and materials can be very hard, in particular in high-β emitters. It is thus challenging to provide input to all the points in the checklist. Assuming the checklist can be completed, is it enough? Interestingly, a cavity-enhanced LED could tick almost all the boxes in the laser checklist, while a thresholdless laser would per definition not satisfy box 1. We therefore claim that determining the change in photon statistics from thermal light below threshold to coherent light above threshold via second-order photon autocorrelation measurements is crucial. This method has largely been ignored by the applied laser community, but is regularly used by the quantum optics community to study photon statistics of emission. Its importance to provide the means to distinguish between a cavity-enhanced LED and a laser is illustrated in Fig. 1.2 The intensity and linewidth dependence on excitation power are very similar for the two devices B and C. However, the equal-time second-order photon autocorrelation function, g(2)(0), is notably different with a clear reduction from 2 to 1 for the laser, i.e. showing a transition from spontaneous to coherent emission.
In summary, we think the laser checklist is much needed and a good initiative by Nature Photonics, that hopefully will improve the quality of published papers, improve the repeatability of results and allow for a better comparison of devices. Even though it may not always be feasible to provide answers to all the questions in the checklist, we should do our best in providing the strongest evidence possible - including excitation power dependent g(2)(0) measurements for high-b lasers - for our claims.
Fig. 1 Performance characteristics for an LED (A), a cavity-enhanced LED (B) and a high-b microlaser (C) in terms of a) optical output intensity, b) linewidth and c) second-order photon autocorrelation as a function of pump power, and intracvity photon number, respectively.
References
[1] https://www.nature.com/authors/policies/laserchecklist.pdf
[2] S. Kreinberg et al., Light: Science & Applications, 6, e17030, (2017).
lasing
nature photonic checklist
Author
Åsa Haglund
Chalmers, Microtechnology and Nanoscience (MC2), Photonics
Stephan Reitzenstein
Technische Universität Berlin
VCSEL day
Ulm, Germany,
Ulm, Germany,
Areas of Advance
Nanoscience and Nanotechnology
Materials Science
Subject Categories
Physical Sciences
Other Materials Engineering
Electrical Engineering, Electronic Engineering, Information Engineering
Nano Technology
Infrastructure
Chalmers Materials Analysis Laboratory
Nanofabrication Laboratory