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  • Qidi Liu1,*,
  • Yusheng Bian2 and
  • Jiawei Xiong3

Reviewer 1: Xing Dai Reviewer 2: Wentao Guo Reviewer 3: Shahram Keyvaninia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents a comprehensive review of silicon photonic passive devices by progressing from the basic waveguide structures to the fundamental components for achieving optical coupling or beam splitting, and from summarising the development and current status of silicon photonic chips to analysing future developmental changes. The entire article gives the impression of being oriented toward providing basic introductions to passive devices and describing their commercialisation process. Chapter 6's summary of currently existing technical challenges and future application areas is quite inspiring. Overall, this is a good-quality and well-organised review paper. However, if the following point can be improved, it would be better for publishing.

  1. It would be better to have the accordingly diagram of each type of waveguide in Section 2.
  2. I have inspected some parameters that lack an explanation in either the text or the figure, for example, in Fig. 2, the W, L, g and the green spots in Fig. (e), which are vague.

Overall, except for those minor points, I would like to support that this paper can be published directly after further editing.

Author Response

please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The content of the paper is comprehensive, providing an overview of the characteristics of various passive photonic devices as well as the latest reported advancements. It also clearly identifies the challenges and development trends currently facing the field of passive silicon photonic devices.

However, there are still some issues in the paper.

  1. In the section on the SiN platform, the transmission loss cited in line 182 from reference [22] is reported as 0.045 dB/m, which contradicts the description in the text. A thorough review is needed to eliminate such discrepancies.
  2. In the edge couplers section, line 297 references Figure 3, yet the figure does not fully depict examples of multi-tip structures. It is suggested to include additional illustrations to address this omission.

  3. The overall quality of the English is clear, easy to follow, and well-structured, with a smooth flow of ideas.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript entitled “Progress in Passive Silicon Photonic Devices: A Review” covers an important and timely topic. However, in its present form, I believe the paper requires major revision before it can be considered for publication. The scope and depth expected from a comprehensive review article are not fully achieved, and the discussion as it stands is rather selective and lacks systematic organization of the literature.

Since the title implies a broad review, the manuscript would benefit from a more comprehensive and structured survey of passive silicon photonic devices, ideally complemented by summary tables. I recommend implementing these revisions to strengthen the manuscript and bring it to the level expected of a review article.

  1. Comprehensive Literature Review
    • A wider survey of the literature should be included.
    • The reviewed works could be organized into meaningful categories, for example:
      • By material platform (Si, SiN, hybrid Si/SiN, etc.)
      • By waveguide thicknesses commonly reported in the literature (e.g., 220 nm, 350 nm, 380 nm SOI, as well as thicker Si/SiN platforms).
  2. Device Characteristics and Building Blocks
    • A comparative overview, preferably summarized in tables and figures, would be very valuable. Suggested parameters include:
      • Waveguide loss and supported wavelength ranges
      • Bend loss and minimum bending radius
      • Fiber-to-chip coupling efficiency (grating couplers, butt-coupling, etc.)
      • Polarization handling (single vs. dual polarization, polarization manipulation options)
      • Nonlinear properties and thermo-optic effects
      • Sensitivity to thickness variations, particularly for devices such as AWGs.
  3. Manufacturability and Foundry Aspects
    • Discussion of wafer sizes used for mass production
    • Availability of foundries and compatibility between different platforms
    • Challenges, especially in relation to subsequent integration with active components
  4. Integration with Active Devices
    • A review of available approaches for integrating modulators, photodetectors, amplifiers, and lasers on these platforms.
    • Consideration of perspectives on co-integration with electronic drivers to provide a complete system-level view.

By systematically categorizing the literature and supplementing the text with comparative tables and figures, the manuscript could offer readers a much stronger and more useful overview of the field. 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript “Progress in Passive Silicon Photonic Devices: A Review” has been improved by the addition of the tables and the latest modifications. I would like to thank you for your efforts. I recommend the manuscript for publication.

I only suggest that the authors perform a final cross-proofread to correct minor English and wording issues before submission of the final version.