Noise Measurement and Reduction in Mode-Locked Lasers: Fundamentals for Low-Noise Optical Frequency Combs
Round 1
Reviewer 1 Report
In the manuscript “Noise measurement and reduction in mode-locked lasers: fundamentals for low-noise optical frequency combs” the authors concisely describe the state of the art on noise detection and noise reduction of mode-locked lasers. The authors detail the main noise mechanisms in mode-locked lasers leading to timing jitter, CEP noise and comb line noise and describe the mathematical model associated with each of these noise terms. Overall, the paper is well organized and written. In few pages, the manuscript gives an accurate review of the mathematical models and the techniques to measure and reduce noise while seemly refers to the relevant work. One remark I have though, I expected a higher level of detail when discussing the use of such noise detection and reduction techniques with the novel comb sources the authors mention, namely EO combs, microcombs and QCL combs. In the outlook, the authors mention “… noise measurement and reduction techniques discussed in this review show significant potential for implementation in such novel frequency combs…” but do not quantitatively justify such argument, besides considering combs with comb spacing in the GHz range. The authors should link the techniques they describe to this type of comb sources by, for instance, identifying the requirements in terms of bandwidth, pulse energy, power per comb line, etc. and next comparing these values with those that can be obtained by the novel comb sources. In particular, there is a huge interest in integrated low-noise OFCs. How are the noise measurement and reduction techniques impact by the limitations of chip-scale active and passive components?
On a side note, I find Fig. 1 not to be self-explanatory. What is the setpoint A and B? The readers should not have to dig into ref. 69 to understand the different plots. Therefore, the authors should either edit the figure or describe properly the different plots
Finally, I found some minor typos that the authors may want to correct. I indicate those in the following. I recommend the authors check the whole manuscript for such typos so that the quality of the review is not decreased.
- “et al.” is an abbreviation of “et alia” and thus should contain a period
- Line 17: lase à laser
- Line 101: note à noted
- Line 107: superscript RN, shouldn’t it be RIN?
- Line 128: serval à several & no comma after that
- Line 172: originates à originating
- Line 186: compare à compared
- Line 192: remove “the”
- Line 198: have à has
- Line 207: limit à limits
- Line 212: SFG not introduced
- Line 214: have à has
- Line 238: remove “two”
- Line 242: “go up as linear of the input power” à “increase linearly with the input power”
- Line 256: AOFS not introduced
- Line 345: “the stablish of a” à “stablishing a”
- Line 348: “overlapping” à overlap
- Line 394: remove “for”
- Line 408: remove “the”
- Line 428: insert “which corresponds to a residual”
- Line 499: insert “resulting in a lower”
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript presents a wide review of the methods for measuring and compensating noises in mode-locked lasers. The text is well-written, technically sound and structured. The following comments may be considered and I hope that it would be helpful in strengthening the paper and clarifying the confusions.
- It would be helpful for a reader to classify the sources of the noises and methods for noise compensation by frequency scales, for instance, kilohertz, megahertz, gigahertz scales. Adding the schematic graph would be preferable.
- Could the authors comment is there any typical types of noises for sources with different energies of the pulses: pJ, nJ, microJ and e.t.c.
- What kind of noises time frequency comb introduce temperature influences?
- Line 185: wrong numbering. Should be 3.1.1. instead of 3.1.2
To sum up, I recommend the manuscript to publish at Applied Sciences journal.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
