Silicon-Based Multimode Complex Bragg Gratings for Spectra-Tailored Filter

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The author has presented a method to tailor the response of a Bragg-grating-based waveguide for reconfigurable photonics circuit. The experiment data matches well with the simulation results. Please find my suggestion below:

 

a) Could the author please add the impact of fabrication errors? To what level of fabrication errors can this device tolerate? The common fabrication errors include waveguide width, height, and side wall angle.

 

b) Could the author please suggest ways to improve the flatness of the band-pass filter?

Author Response

Please, see the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This work introduces a spectral tailoring methodology enabling physically realizable design of MWBGs with complex responses, and experimentally confirmed it. I think it can be accepted after minor revision:

1. The expressions in Eq.1 are not standard form of Gaussian function. It is recommended to add its reference.
2. The article clearly states that the original impulse response of the target spectrum in Figure 2(a) is non-causal. Why, then, did Figure 3 adopt the range of -50~50 fs from Figure 2(a), rather than using the range of 50~150 fs from Figure 2(b) as the control group for the truncation window size of 200 fs?
3. In Figure 5, the "Δw" can be marked with vertical double-headed arrows (similar to the annotation for "W") to more explicitly indicate the parameter's position.
4. The term “square” in Fig.5 appears to be a format used in the program, and it is recommended to make modifications.

Author Response

Please, see the attached file.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This paper presents a methodology for designing and fabricating complex, spectra-tailored Multimode Waveguide Bragg Gratings (MWBGs) on a silicon-on-insulator platform. The authors demonstrate this technique by realizing a multi-channel Gaussian-shaped filter, and the experimental results show a good general agreement with the design, proving the viability of the proposed approach. I would recommend this manuscript for publication in Photonics after the authors have addressed the following concerns:

1. The experimental results indicate a redshift of the central wavelength and a broadened 3-dB bandwidth, which the authors attribute to fabrication errors. It would strengthen the paper if the authors could provide a more detailed analysis of which specific fabrication parameter deviations would lead to these results. Further, could this analysis be verified through the provided SEM measurements?
2. A grating length of 587.76 μm is not ideal for many applications in integrated photonics. A discussion on potential methods to reduce the device footprint would be a welcome addition.
3. The introduction would benefit from more references to support the discussion on potential applications, particularly in lines 54 to 56.

Author Response

Please, see the attached file.

Author Response File: Author Response.docx