λ-Scale Embedded Active Region Photonic Crystal (LEAP) Lasers for Optical Interconnects^†

Round 1

Reviewer 1 Report

This is an invited paper written by the authors who have been developing so-called LEAP papers. LEAP lasers are one of promising laser devices that can be applicable to the future highly-integrated optical interconnect systems with high speed and low power consumption. In the manuscript, the concept and the recent progresses of LEAP lasers arte well introduced. So, the reviewer thinks it is definitely worth publishing the paper in this journal. Before the publication, to increase the impact of the invited paper, the reviewer would like to suggest the authors to consider the following points and to reflect them in the manuscript if they can agree.

1)     As an invited paper reviewing the progress of LEAP laser, it would be very nice if the authors could provide the future prospects from wider viewpoints.

2)     In section 2, the authors explain the small difference in refractive indexes between the embedded active material and the surrounding material. It will be helpful if the figures of the index are provided.

3)     Figure 1 (a) is not clear enough. It is almost impossible to recognize the PhC in the figure. Please put a clearer illustration.

4)     In page 2, line 68: Should “reducing the temperature” be “reducing the temperature increase”?

5)     Brushing up English expressions will make the paper much easier to read.

Author Response

Thank you for reviewing out paper. First of all, we asked to revise our manuscript for native English speaker and this is a revised version.

Reviewer 1

1)     As an invited paper reviewing the progress of LEAP laser, it would be very nice if the authors could provide the future prospects from wider viewpoints.

We have added following sentences in pages 7 and 8.

Integration of Si photonic devices will open new application areas for PhC nanodevices, or PICs, for optical computing in deep learning, neuromorphic computing, and so on. This is because such computing requires sophisticated optical circuits based on Mach-Zehnder interferometers, which are integrated with low-power-consumption PhC devices made with III-V materials, such as lasers, switches, and nonlinear components.

Recently, we have successfully demonstrated the fabrication of a LEAP laser, in which active region is a single lattice constant (~420 nm) [23]. By expanding this, we can fabricate periodic buried active regions, which will enable us to improve the device performance by introducing interesting phenomena such as parity-time (PT) symmetry [24]. 

2)     In section 2, the authors explain the small difference in refractive indexes between the embedded active material and the surrounding material. It will be helpful if the figures of the index are provided.

We have added following sentence in figure caption of Fig. 1.

Since the refractive index of the active region is slightly higher than that of InP, an optical cavity is created around active region without shifting the positions of the air holes. Typically, the effective refractive indexes of the InGaAsP-based active region and the InP layer are 2.77 and 2.59, respectively.

3)     Figure 1 (a) is not clear enough. It is almost impossible to recognize the PhC in the figure. Please put a clearer illustration.

We have revised Figure1 (a).

4)     In page 2, line 68: Should “reducing the temperature” be “reducing the temperature increase”?

Thank you very much. We apologize this mistake.

5)     Brushing up English expressions will make the paper much easier to read.

Reviewer 2 Report

The paper is very clearly and well written. The problem considered in the paper is very important for practice and the experimental results are significant. I suppose that the paper can be published in Photonics.I would like to note that the authors need to correct the unnecessary article 'the' in the Conclusions in the sentence "We the grow an InPlayer ...". 

Author Response

Thank you for reviewing out paper. First of all, we asked to revise our manuscript for native English speaker and this is a revised version.

The paper is very clearly and well written. The problem considered in the paper is very important for practice and the experimental results are significant. I suppose that the paper can be published in Photonics. I would like to note that the authors need to correct the unnecessary article 'the' in the Conclusions in the sentence "We the grow an InPlayer ...".

Thank you for letting know our mistake. We have revised.