Review Reports

Round 1

Reviewer 1 Report

High Power laser diode emitting around 793nm is mature and commercialized, and the power of the laser that can be purchased is larger than the results obtained by the authors. Therefore, the authors need to explain the innovation of their experimental design, otherwise, the paper can not be published.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This article has successfully completed the design and development of a 792 nm high-power semiconductor laser chip, also has been well applied. The issues of concern are shown as below:

 1. The article describes the structure design of the laser, but the preparation process is placed at the end of the introduction, and should be adjusted to the appropriate location to explain the processing sequence of the laser chip.

 2. The abbreviation 'BPP' should be “beam parameter product” instead of “optional parametric product" .

3. The article mentions that 24 pieces of 792 nm lasers are commonly used “24 792 nm lasers”, which can easily lead to misunderstanding and should be modified to 24 × 792nm chips or 24 pieces of 792nm laser diode.

 4. Some punctuation marks are missing, such as “.” In line 115.

The output power of the coupling module completed by the author of this paper is significant. Due to similar reports, it is recommended to conduct in-depth research to further explore the coupling efficiency limitation.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The paper describes the design and evaluation of a laser module emitting at 792 nm which is based on the incoherent spatial beam and polarization combining of 24 laser chips in a single multimode fiber. The output power reaches 232 W with an electrical-to-optical conversion efficiency of about 49%. Aging tests over 4000 hours result in no obvious decrease of the optical power. The laser module is specifically designed for the pumping of Tm:doped crystals.

The approach chosen by the authors is well documented in the literature; it is also quite established among laser manufacturers (BWT, Coherent, nLight…). The novelty of the work appears then limited for a research paper. In addition, the references do not provide a proper state-of-the-art in the field of high-power laser diodes and fiber coupled diode laser modules, which is the core of the paper. The results obtained with the single emitters are not compared to others.

Eventually, I have multiple comments regarding the description of work, which should be significantly improved. I have made a list of suggestions in the joined document. As a consequence, I do not recommend publication of the paper in this current form and suggest that the authors improve it before considering re-submission.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors refer to nlight and point out that their optimal core diameter of 793nm and 200μm is over 200W. In fact, nlight's 400W products, such as element e24i, are now available in the same wavelength band with smaller Na-fibers. Not to mention the commercial products of some semiconductor laser companies in China such as everbright, the output power of their laser single chip (more than 35W) and fiber coupling (more than 600W) has far exceeded the power mentioned in this paper，and this is available for commercial use. So the author needs to further clarify the innovation of this paper and the guiding significance to the peer.

I am glad to see that the authors have proposed a more specific interpretation of the innovation. However, whether asymmetric waveguide, strained QWs or aluminum-free active region, these technologies have been widely used in GaAs-based semiconductor lasers. If the authors emphasize that their structure is innovative, then the device results, whether single chip, bar or laser module should at least present a move forward. Otherwise, the results of widely used classical structures are weaker than those of commercial devices, which can hardly arouse the interest of relevant practitioners, and a lack of clarity about the industry situation can lead to serious misleadingness.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

I acknowledge that the authors have answered precisely and thoroughly to most of my comments and questions, and have made the suggested changes in the revised version. Nonetheless some clarifications are still required on two points that I have already mentioned in my first review, which have not been clearly handled in my opinion.

As such, I believe that the paper still needs some improvement before publication. In the joined document, I have made a list of the few points which should be corrected in the revised version. 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx