Single-Longitudinal-Mode Laser at 1123 nm Based on a Twisted-Mode Cavity
Round 1
Reviewer 1 Report
The authors have achieved satifactory 1123nm TEMoo mode laser emission by Nd:YAG rods, however, to justfy its possible publication by Crystals, large revision is needed.
Mainly, the authors should explain in detail the technical advantages of their work in relation to the most recent and the most efficient TEM00 1123nm Nd:YAG laser, as indicated below:
Most recent publication in 2020 (Optics Express)
106.5 W high beam quality diode-side-pumped Nd:YAG laser at 1123 nm
https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-18-8-7923&id=196995
The best TEMoo-mode (Transversal mode) 1123nm laser (Applied Optics)
https://www.osapublishing.org/ao/abstract.cfm?uri=ao-38-27-5761
Efficient operation of a Nd:YAG laser on the low-gain 1123-nm transition by end pumping with the reshaped output from a 7-W diode bar is reported. Using a simple standing-wave laser configuration and pumping with 5.6 W of incident power yielded a laser output power of 1.7 W in a near-diffraction-limited TEM00 mode with a beam quality factor of M 2 ≲ 1.1. A unidirectional single-frequency ring laser was also constructed, yielding 180 mW of single-frequency output.
Besides, the quality of the figures (Fig. 3 and Fig.4 for example) should be significantly improved with much more resolutions ( inset figure with nm scale can be added). The vertical axis value of the Fig.4 is not readable.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors,
This paper describe fairly obvious results, and I see no novelty.
There are single-frequency laser at 561nm commercially available.
For example, https://www.ksoc.co.jp/en/seihin/lasers/561_100mw.html
What you call “L-cavity” is not with a Brewster’s window. It must be coated for high reflectivity for s-polarization so this is a “polarizer” or “polarizing beam splitter”. The fact that the “linear cavity” showing higher threshold and lower slope efficiency seems to indicate the Brewster’s window may not have been correctly angled, or lossy for p-polarization if this was coated. This needs more discussion.
The measurement of M^2 is not compliant with ISO11146, which states in its Section 9 of Part I, “… Hence, measurements at least 10 different z positions shall be taken. Approximately half of the measurements shall be distributed within one Rayleigh length on either side of the beam waist, and approximately half of them shall be distributed beyond two Rayleigh lengths from the beam waist.”
Lack of novelty, or in-depth technical discussion make me recommend rejection.
I also wonder if this is a topic (laser operation) to be covered in Crystals.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The revised manuscript has enough quality to justify its possible publication by Crystals
Author Response
Thank you very much for your recognition of our article.
Reviewer 2 Report
The product page https://www.ksoc.co.jp/en/seihin/lasers/fs_compact_kikaku.html
clearly states 561nm laser being single longitudinal mode.
None of the issues I raised in the previous review is being addressed.
I cannot recommend its publication.
I recommend rejection.
Author Response
Plsase see the attachment.
Author Response File: Author Response.docx
