High-Bandwidth Lumped Mach-Zehnder Modulators Based on Thin-Film Lithium Niobate

Round 1

Reviewer 1 Report

This paper presents a comprehensive optimization on lumped TFLN modulator and solid results. As far as I know, lumped TFLN modulators have not been well studied yet and this modulator could offer a bettern tradeoff between compact size, high efficiency, and high bandwidth. Thus, I recommend acceptance for this paper.

Author Response

We are very grateful for your kind appraisal. Thank you for your time and dedication in reviewing our manuscript. We are honored to have had the opportunity to receive feedback from someone with your level of expertise.

Reviewer 2 Report

The paper presents a lumped Mach-Zehnder Interferometers (MZI) based on Thin-Film Lithium Niobate. By designing the device with capacitive loaded lumped electrodes, the proposed MZI breaks the trade-off between EO bandwidth and VπL of conventional lumped MZI. The low VπL of 1.15Vcm and 32.4 GHz is achieved by a 1.5 mm device. The paper is clearly written and coherent. The architecture and the analyses for it look promising. However, there are few minor concerns need to be addressed:

1. The cross mark in Figure 6 c-e and Figure d-f are too small to see. Utilizing bolder marks could substantially improve visibility and comprehension.

2. As author mentioned, CL-LE structure breaks the trade-off between EO bandwidth and VπL. It further demonstrates, particularly in Figures 8 (d-f) and Figure 9b, that increasing the Electrode Gap (S) and decreasing the Electrode Width (W) leads to a reduction in both capacitor and power consumption, while simultaneously increasing the bandwidth and inductance. This prompts the question of why the smallest possible Electrode Width alongside the largest Electrode Gap was not selected, given its apparent superior performance. Are there additional constraints on the CL-LE structure that extend beyond the trade-off between EO bandwidth and VπL?

3. The manuscript mentions the use of a relatively high input power of 14 dBm for the eye diagram test. This raises questions regarding the insertion loss of the Mach-Zehnder Modulator (MZM) and whether the CL-LE structure might introduce additional insertion losses when compared to the C-LE structure. More discussion about the insertion loss is needed.

4. There is a discrepancy in the reported VπL values; Line 256 mentions 1.13 Vcm, which is different from the abstract and conclusion which state 1.15 Vcm. Ensuring consistency throughout the manuscript will enhance its credibility and accuracy.

Author Response

Thank you very much for your valuable suggestions, we have responded to your comments in detail and made changes in the revised version.

Author Response File: Author Response.pdf

Reviewer 3 Report

Yang et al. presented a new design for lumped Mach-Zehnder electro-optical modulators, using novel capacitive loaded lumped electrodes. According to their simulations, their design shows better specs, including high bandwidth and low power consumption. This manuscript can be a timely addition to the literature, and can find potential application in optical communication.

This manuscript is very well written. It introduced and experimentally verified their electro-optical model, and then used this model to simulate various designs. In the end they compared the specs that they achieved in this work with the state of the art in literature. Therefore, I recommend the publication of this paper.

I have a minor comment though. Since this work presents an enhanced EO modulator based on lumped MZM, it would be useful to put it in the broader context of all types of EO modulators. How does the specs (bandwidth, energy consumption) achieved in this work compare to those achieved in other types of EO modulators?

Author Response

Thank you very much for your valuable advice. We very much agree that lumped electro-optic modulators should be compared in a broader context.

Author Response File: Author Response.pdf