Influence of Radiative and Non-Radiative Recombination Lifetimes and Feedback Strength on the States and Relative Intensity Noise of Laser Diode
Round 1
Reviewer 1 Report
The manuscript considers the dynamics and noise properties of semiconductor lasers with optical feedback when both radiative and non-radiative recombination rates are considered. The laser is shown to operate in different regimes, including continuous-wave, periodic (with harmonics) and chaos. The inclusion of different recombination rates is important and the results are clearly organized, and I believe the work could be published after some language editing. Some of the English is not very straightforward and there are spelling issues (e.g. “noise sources” in figure legends).
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript by Abdulrhmann et al. represents a work on numerical modeling of the behavior of diode lasers under external feedback using a rate equation approach. Unfortunately, there is no comparison with experiments. This type of modeling cannot be directly examined by the reviewer, simply because it would require the reviewer to simply repeat the authors' work. The modeling was done specifically for one application case, namely diode lasers for the 1.55 µm optical fiber range. Even if the authors do not say it explicitly, one must add further restrictively that it concerns a single-mode diode laser in continuous-wave operation. This is, of course, a rather special case. On the subject of external feedback in diode lasers, there have been many papers for decades, some of which are referred to by the authors. Nevertheless, this subject is undoubtedly still interesting, because very many phenomena related to diode lasers are not understood, which are very likely due to external feedback.
Some remarks:
We are somewhat surprised that the very early work of O. Hess is not cited.
There is a very recent paper by the authors, namely - Salah Abdulrhmann and Ahmed Hussein Msmali „Numerical analysis on the impact of optical feedback and nonlinear gain on the dynamics and intensity noise of semiconductor laser“ Applied Physics B volume 128, Article number: 113 (2022). Could the authors please explain clearly what is the added value of the current work over this other one?
It is clear that the RIN is an important parameter for the operation of diode lasers for fiber optic communication. Nevertheless, at this point the authors should again explain in detail the significance of their numerical simulation, for example, for the data transmission rate of such devices.
All in all, we are of the opinion that the present work is interesting, but only makes a very small contribution to our understanding of the matter.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The reviewed manuscript reports on study of the properties of semiconductor laser radiation, and I have the following to share in this relation:
1. The presented work is purely theoretical, without any experimental corroboration. It is not obvious how closely the proposed analysis matches the reality. It is necessary to provide at least some experimental data that would substantiate the numerical results.
2. The calculations are performed in certain approximations, which need to be spelled out in the Conclusion.
3. The calculations use a semiconductor laser with an external cavity. A diagram of this cavity should be given, as well as a comment about those calculations specifically for this configuration. What type of semiconductor lasers was factored into the calculations? Were they performed for diode lasers with external cavity (single-frequency lasers?) or for diode lasers without such an external cavity? Clear comments are needed that will not allow any ambiguity.
4. It is not evident how novel and original the proposed calculation is. It is pretty certain that similar studies have been done before. Hence, it is necessary to explain why this design is better than the earlier ones.
If these concerns are addressed in a further revision of the manuscript, it may be published in Photonics
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have adequately addressed the issues raised by the reviewer.
Therefore, the work can be published.
Author Response
Reply to Reviewer’s Comments
Reviewer 2#
We appreciate the contribution of the referee for his/her valuable comments which reflected positively on our present work.
Following is our response to the referee's comments as well as the changes made in response to these comments:
Response to the referee:
Comment# 1:. The authors have adequately addressed the issues raised by the reviewer.
Therefore, the work can be published.
Our response: We appreciated the contribution of the referee for valuable comments.
Reviewer 3 Report
The Authors have presented a new version of their manuscript amended according to the voiced concerns. However, the results of these amendments have not been clearly indicated (for instance, by highlighting). This is why it is difficult to understand where and to what extent the comments were taken into consideration. As an experimental corroboration, the Authors refer to publications [17] and [26], which are 19- and 20-year old respectively. When answering the question of novelty and originality of their modelling, they refer to works [15, 16] published in 1986 and 1980, correspondingly. It is important to demonstrate the topical character of the conducted research and importance of the produced results for the development of contemporary semiconductor lasers. If the Authors revise their manuscript in line with these comments, it may be published in Photoniсs.
Author Response
Reply to Reviewer’s Comments
Reviewer 3#
We appreciate the contribution of the referee for his/her valuable comments which reflected positively on our present work. We have addressed all the referee’s questions, and comments, and made the necessary changes to the present manuscript. A list of changes made in the manuscript is underlined throughout the manuscript.
Following is our response to the referee's comments as well as the changes made in response to these comments:
Response to the referee:
Comment# 1:.
The authors have presented a new version of their manuscript amended according to the voiced concerns. However, the results of these amendments have not been clearly indicated (for instance, by highlighting). This is why it is difficult to understand where and to what extent the comments were taken into consideration. As an experimental corroboration, the Authors refer to publications [17] and [26], which are 19- and 20-year old respectively.
Our response: In the revised manuscript, Refs. [17 and 26] are added to clarify, and confirm the power of the model used in the calculations. These Refs clear a good fit between experimental results and calculations using the model used in this article. Please refer to Figs (5-8) and its explanations on the solitary laser and Ref. [26]. In the revised manuscript, we have shown in figures 5-9 the contribution of the noise on carrier lifetime and radiative and nonradiative recombination rate which is in good agreement with the reported results in Ref. [26]. Please refer to a new add Fig. (9) and its explanations.
When answering the question of novelty and originality of their modeling, they refer to works [15, 16] published in 1986 and 1980, correspondingly.
Our response: We apologize to the referee. It was mistyping in the report, we mean Refs [17 and 18].
It is important to demonstrate the topical character of the conducted research and the importance of the produced results for the development of contemporary semiconductor lasers. If the Authors revise their manuscript in line with these comments.
Our response: The radiative and non-radiative recombination processes influence the efficiency of light emission, and hence the threshold condition of semiconductor lasers. However, based on our knowledge, there is no investigation till now on the impact of the OFB strength and the ratio tr/tnr on the dynamics and RIN of SL. In this paper, we propose a newly numerical analysis of the impact of OFB and the ratio of the radiative and the non-radiative recombination lifetime tr/tnr on the dynamics and intensity noise of SL. The added values of the current work are: the route to chaos is depending on the ratio tr/tnr, and injection current. In the route to chaos regime, the ratio tr/tnr causes a slight frequency shift relative to the frequency of the solitary laser. At higher levels of the injection current, the highest value of the ratio tr/tnr stabilizes the laser and stimulates it to operate in CW or PO. In the strong OFB regime when the ratio tr/tnr increases the chaotic operation changes to CW or PO operation and the RIN is suppressed near the quantum noise level. A good understanding of the impact of the carrier recombination mechanisms in SLs on the dynamics and intensity noise is essential for designing SLs with high static and dynamic performance. In this paper, we determined the best ranges of the ratio tr/tnr, OFB strength, and injection current, which can be used to stabilize the semiconductor laser and operate it with low noise, improving the performance of SLs.
Round 3
Reviewer 3 Report
The Authors have once more presented a revised version of their manuscript. Nevertheless, certain questions still remain, for I have not received an explicit and clear answer to them. I will repeat them here once again:
1. The calculations are based on a semiconductor laser with an external cavity. It is necessary to supply a diagram of this cavity and to substantiate somehow the choice of modelling this particular configuration. For which type of semiconductor lasers have the presented calculations been carried out? For external-cavity diode lasers (single-frequency lasers?) or for diode lasers without an external cavity? This should be stated in the manuscript.
2. It is not immediately obvious, how novel and original the presented modelling is. Undoubtedly, similar modelling has been performed in the past. Hence, it is necessary to point out why the proposed calculations are better than the previous ones (and which ones, and in what respect).
Apart from the above, the Conclusion should be augmented with some practical recommendations following from the reported results.
If the Authors take into consideration these comments in a further revision of their manuscript, it may be published in Photonics.
Author Response
Reply to Reviewer’s Comments
Reviewer 3#
We appreciate the contribution of the referee for his/her valuable comments which reflected positively on our present work. We have addressed all the referee’s questions, and comments, and made the necessary changes to the present manuscript. A list of changes made in the manuscript is underlined throughout the manuscript.
Following is our response to the referee's comments as well as the changes made in response to these comments:
Response to the referee:
Comment# 1:.
The calculations are based on a semiconductor laser with an external cavity. It is necessary to supply a diagram of this cavity and to substantiate somehow the choice of modelling this particular configuration.
Our response: In the revised manuscript, we have added a new figure (Fig. 1). Please have a look at Fig. 1 and the explanation (Line: 79, 80, and 84).
For which type of semiconductor lasers have the presented calculations been carried out? For external-cavity diode lasers (single-frequency lasers?) or for diode lasers without an external cavity? This should be stated in the manuscript.
Our response: We would like to highlight that in this work we have presented a new detailed characterization of the dynamics of InGaAsP/InP lasers emitting at 1550 nm, and operating under OFB with an external cavity (single frequency lasers). Please have a look at Lines: 70-72, 141-153 in Sec.3, and table (1), in the manuscript.
Comment# 2:.
It is not immediately obvious, how novel and original the presented modelling is. Undoubtedly, similar modelling has been performed in the past. Hence, it is necessary to point out why the proposed calculations are better than the previous ones (and which ones, and in what respect).
Our response: The improved rate equations in our model are applicable for an arbitrary strength of OFB and, as shown in Figs. 2 and 3, were used to introduce detailed characterization of laser dynamics under a wide range of OFB from very weak to strong OFB. The reviewer is requested to see our citing to this work in the Introduction, lines 39-47.
In this citation, we cleared the importance of our model compared with similar models such as the works by R. Lang and K. Kobayashi cited as reference [16], lines 39-47. The work by Langly et al. concerned only with the regime of transition from moderate OFB-induced coherence collapse to stable operation under stronger OFB. Such a model generalized the Lang-Kobayashi model only by counting multi-reflections due to OFB, which is not enough to account for the strong OFB. Also, the Lang-Kobayashi model is applicable to the case of weak and moderate OFB (as derived mathematically from our model in Ref. [17]). Therefore, such a model is not used to analyze laser dynamics under strong OFB, such as in the case of lasers pumping fiber amplifiers (AR-coated facet).
Comment# 3:.
Apart from the above, the Conclusion should be augmented with some practical recommendations following from the reported results.
Our response: In the revised manuscript, we have added some practical recommendations to the conclusion. Please have a look at the explanation (Lines: 402-414).
Author Response File: Author Response.pdf
