Optimal I–V Curve Scan Time for a GaAs Laser Power Converter

Round 1

Reviewer 1 Report

The authors demonstrated 6-cell laser power converter based on GaAs technology, in order to test and scan reliably its IV characteristics. The input laser light wavelength is tuned to 1550 nm. The design comprise of several sub cells connected with tunnel junctions in series. The authors did thorough analysis of IV characteristics due to charging and discharging of the parasitic capacitances, and as function of time and the temperature. Based on all that they have found the optimal time for the measurement of reliable IV characteristics of LPC devices. The paper clearly contribute towards the development of the "post silicon (opto)electronics" and I can recommend it for publication in journal "Photonics," after minor but compulsory clarification below:

 

 

1) Does the device works in the current matching regime? And if not for how much the sub-cells current deviates form the total current (Imeas) trough the device?

2) Can the authors estimate and give the values of the equivalent circuit components C1-C5, in particular, but also Rsh1-Rsh6?  If someone is to replicate device on the breadboard model?

 3) For their set up the authors used 1550nm laser that is GaAs sub-band gap illumination? Typically, the LPC offers the best performance if the laser light and Eg of the devices are tuned? Can the authors clarify this point?

4) Can the authors clarify how they have estimated the individual thicknesses of sub-cells, and their doping profile of depletion layers, hence their absorption abilities, in their LPC design? This is related to the current matching question. I presume they have used Beer-Lambert law, to estimate the individual thicknesses. Recently, there were put forward methods based on machine learning and genetic algorithm, that can estimate the individual thicknesses of the LPC-VEHSA, or MJCS, please see: "Genetic algorithm designed high efficiency laser power converters based on the vertical epitaxial heterostructure architecture," SOLMAT,  Volume 200, 15 September 2019, 109878. and "Automated design of multi junction solar cells by genetic approach: Reaching the > 50% efficiency target" Solar Energy Materials and Solar Cells, Volume 181, July 2018, Pages 30-37. The ML model suggest that, in particular when estimating the first layer in the stack the B-L model might be underestimating the thickness of the first-sub-cell, hence undermining its ability to absorb (producing current)? Would it be possible to explain the appearance of hysteresis in certain cases, due to mismatch between the sub-cell thickness and characteristics of the tunnel junctions?

minor editing like page 3/11, line 113, "is asme as" should be "is the same as"

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

1.     Introduction section, line 27-29: Is there a reference for this statement?

2.     Line 63: The authors should elaborate on what “AOV” is.

3.     Line 80: Could the authors discuss what impacts internal capacitance?

4.     The authors may consider combining figure 1/2/3, since they are related.

5.     Section 2.3 seems deviated from the major claim of this manuscript.

6.    The authors may consider combining figure 4/5, since they are related.

7.  Figure 6/7 have less innovation to support the major claim of this manuscript. The authors may consider combining them with other figures.

8.  Figure 8/9 seems logically confusion in terms of whether the study has TEC on, and how to rule out the thermal effect as of laser illumination time.

9. All figures need to improve for data presentation cleanliness and clearness. The format/font of x/y label and legend should be consistent over all figures. The plot lines in all figures should be visible enough for audience to read.

10. The authors should consider discussing more on how this work (which is specifically for one GaAs based LPC) could benefit the experimental works of other photonic devices, and what values (e.g. experimental principles, design rules, etc.) can the broad audience from photonics world obtain from this study.

Overall, this manuscript seems needing improvement in (1) data presentation, (2) logical discussion of the results, (3) deeper/further impact for broad photonic research, in order to meet the standard to publish in Photonics journal.

Moderate English modification is needed. Examples are listed below.

1. Abstract section, line 14, there should be a coma before “is presented”.

2. Line 58: there should be an “the” before “thermalization loss” to be consistent with “the transient effect”

3. Line 81-82: the word "can" needs to follow by "observe" instead of "observed".

4. Line 184: "uder"  "under".

5. Line 188: “(TEC)” should be after “thermoelectric cooler”.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Included in the file. 

Comments for author File: Comments.pdf

Some sentences requre thorough proofreading like "Calculating the difference between the two new curves." (line 213). 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. The authors should consider combining Figure 1c and Figure 2, since they are very similar.

2. Again, I don't see enough innovation from Figure 5. What are the advantages or improvement of the setup compared the widely used setup in academic and industrial research?

3. The format of Figure 7/8/9/11/12 are not consistent, for the font of the texts/labels/legend as well as the format of "variable (unit)".

4. Figure 11 is missing from the manuscript.

Extensive English polish is needed. The examples include but are not limited to:

1. Line 74: I don't quite understand what this sentence meant.

2. Line 222-223: This is not an English sentence with subject + verb + object.

3. Line 245-246: This sentence is hard to understand.

4. Line 276-277: "which means needing more time requires xxx" English grammar issue.

5. Line 277-279: This is not an English sentence.

6. Line 279: character --> characteristics

7. Line 283-284: This is not an English sentence.

8. Line 293: base on --> based on.

9. Line 293-294: This is not an English sentence.

10. Line 301-302: This is not an English sentence.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Article can be published in current form. 

Author Response

Thank you for taking time out of your busy schedule to read our manuscript and giving us a lot of constructive suggestions. We gratefully appreciate for your the  recognition.

Round 3

Reviewer 2 Report

Thanks for the author's response to my previous concerns and questions. Most of them have been successfully addressed. Now this manuscript appears better than the previous versions.

However, there are still several format and English language issues that the authors should modify further in order to meet the publication standard.

For the format, the x/y labels of Figures 5-9 are still not fully consistent. Sometimes the labels start with upper letter, sometimes they start with lower letter. Also, there are several places missing a space between number and unit (for examples, line 84, line 88).

For the English grammar issues, please refer to the next section.

1. In line 275, the word "The" should be "the".

2. Line 283: "the algorithm is not limited to different materials LPC". It is not clear on what this sentence means.

3. Line 292-293: this sentence should be changed to "the Pmax and FF tend to be stable at around 10 ms".

Author Response

Please see the attachment.

Author Response File: Author Response.pdf