A 1 × 4 Silica-Based GMZI Thermo-Optic Switch with a Wide Bandwidth and Low Crosstalk

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents a GMZI structure designed and fabricated on a silica platform, exhibiting an insertion loss of −6.51 dB, a crosstalk suppression of −17.27 dB. The device achieves low crosstalk over a wide bandwidth, showcasing innovative features. These results support its publication in Photonics.  However, several technical details require further clarification:
1.The state calibration of 1×N switches is relatively difficult. How is each state of the switch calibrated? Why is there such a difference in power consumption for each state?
2.Are the length and width axes mislabeled? The Y-axis seems to represent width, while the X-axis represents length.
3.The Y-axis label in Figure 5(b) should specify 'worst crosstalk'.
4.Why was the response time of Channel 1 measured at Output State 3?

5. Use passive voice to describe test results，For example，Lin135 :“We measured the device's response speed.” and Line 138: "We measured the rise and fall times...."  should be " the device's response speed was measured...", "the rise and fall times were measured..."

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In the manuscript, the authors proposed a 1×4 silica-based GMZI thermo-optic switch with wide-2 bandwidth and low-crosstalk. The thermo-optic switch fabricated on a silica platform enables flexible switching among four output channels and presents a cross-talk below -15 dB over the 1500–1580 nm wavelength range and an insertion loss of -6.51 dB at 1550 nm. The topic is interesting, and I support it for its publication in Photonics. I have some minor points that I would like to be addressed in the manuscript before its publication:

1. To achieve minimal crosstalk and lowest insertion loss, the input/output ports of each MMI incorporate three identical-length tapers with varying widths. But why still need to use the taper structure on the output waveguides?
2. Why is the rise time of the device less than the fall time? How to reduce the response time?
3. The power-consumption of the device seems to be a bit high. How to reduce the power-consumption of the device?
4. Figures 6(b)-6(d) are a bit blurry and the clarity of the figures needs to be further improved.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript reports a 1×4 Silica-based GMZI thermo-optic switch. To improve the manuscript further, the authors may want to consider the following suggestions.

#1. The title of the manuscript is A 1×4 Silica-Based GMZI Thermo-Optic Switch with Wide-2 Bandwidth and Low-Crosstalk。The bandwidth of the switch should also be compared with published results.

#2. Authors should explain clearly about the thermo modulation of the switch.

#3. The influence of the tapered waveguide structures on the transmission of the 1×4 MMI, is suggested to be analysed in simulation.  

In summary, I recommend the manuscript for publication in Photonics after major revision.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

1. A general formatting issue: there should be space between and after all references citation in the manuscript, please fix.
2. The index difference between the core and cladding is so small, leading to a very loosely confined optical mode. Can the author provide mode simulation? With such a loosely confined mode, what is the metal to core distance design to avoid metal loss? What is the trade off of the thermal tuning effect? All these aforementioned design and simulation are necessary, and should be included and discussed. 
3. The author present an interesting taper design in figure 1, but there is no presentation in design to support “to achieve minimal crosstalk and lowest insertion loss”.
4. Figure 2 lacks a proper description. What is CH1-4? They should be labeled with diagrams. The author mentioned x-axis being width and y-axis being length, but that is not what figure 2 is showing, which is a spectrum plot.
5. Again, table 1 has no description of what WT1, Lt, W1, W2, etc are.
6. The switching condition is poorly described and represented in table 2. Output 1-4 status should be described better with diagrams, especially as they are mentioned several times across the manuscript. Whatever is represented in the figure and table should correspond to the context in the manuscript, and vice versa, And the power consumption of 689 mW for a thermo-optic switch is huge.
   
   Overall the paper is not well written, with a lot of technical details, design and discussion missing, the figures and tables are not well presented.
   

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript is well revised, and I recommend to be published.