Stresses Produced in the BK7 Glass by the K⁺–Na⁺ Ion Exchange: Real-Time Process Control Method

Round  1

Reviewer 1 Report

The authors report on a way to assess glass stress parameters after ion-exchange starting from the measurement of the propagation constants of the modes of the waveguide created by the process.

This is a well established technique and a more detailed literature search should be carried out (by me) to judge the innovation proposed by the author in the manuscript.

But, before going ahead, I noticed that in the whole article the author only mentions the geometrical reasons (e.g. volume change due to the different ionic radii of the ions involved in the ion-exchange) which cause the refractive index change of the glass, totally neglecting the well known effects of the different electronic polarizability of the ions (which are very different for Na⁺ and K⁺).

Though I understand that the focus of the paper is on stresses and therefore limited to the geometrical effects, I think that not mentioning this even in the introduction can be misleading for a reader not expert in the field.

But what is worse, is the fact that these effects are neither mentioned nor taken into account in the technical part of the paper.

Here I must therefore raise my concerns about the soundness of the whole paper.

I do not exclude that an assessment based on the content of the paper is feasible. Better said, I am positive about this.

Actually, the polarizability effect is isotropic. Therefore, many of the assumptions made by the author could still hold.

But in a properly written paper, I would expect all the effects to be considered, their effect taken into account or ruled out after a discussion, albeit brief.

Therefore, I admit I stopped examining in detail the rest of the theoretical and experimental section of the paper, since I think that, without the details mentioned above, there is no point in going further at this stage.

Moreover, the author writes in the conclusions that it is not possible to determine the refractive index profile of a graded index waveguides with less than 5 measured modes.

Of course, the more experimental data you have, the better it is in terms of precision of the parameter you obtain from a fit procedure, as always.

I am very aware about this.

Nevertheless. in principle and depending upon the theoretical framework used for the refractive index reconstruction, even 2 modes can give a result, though of limited precision.

But then it must be discussed the minimum level of precision needed, not state that 5 is the bare minimum for any result, approximate or not (then why 5 and not 4 or 9?).

Author Response

Please find attached the response to the reviewer’s comments.

Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, the author investigated stresses produced in BK7 glass using the K+↔Na+ ion exchange  method. The principle of monitoring stresses in the real time of diffusion processes was verified by comparing the stress values obtained from measurements of glass samples using optical method with the results from a real-time simulation. Both the diffusion process and heating process were investigated.

The theoretical study is complete. The simulation results agree with the experimental results. The investigation is complete and could be used for the study of one-dimensional stresses in planar structure. However, the reviewer has the following comments with respect to the writing and arguments in this manuscript. This paper should be accepted after all the required revisions are made and the questions are answered.

1.      The author should improve his/her English writing skill. There are lots of typos and improper expressions in this manuscript.

·         In the abstract, it should be 370 to 402 degree Celsius.

·         In the axis ticks of figures, the decimal point should be dot other than comma.

·         It is better to place the x-label below the x axis and plate the y-label on the left of the y axis.

·         Be more rigorous when use semicolon. Such as, “On the basis of elastooptic coefficients; the resulting stresses were determined.” The semicolon should be replaced by comma.

2.      In Eq. 1, C1 and C2 are named as elastoopic coefficients. However, in Eq. 2, p11 and p12 are also named as elastoopic coefficients. Is this correct?

3.      In line 110, the plate with a dimension of 12 mm by 30 mm by 1.5 mm was used. Does the dimension of the waveguide have any influence on the measurement of stress? In other words, does waveguide dispersion has effect on the measurement of stress?

4.      In Fig. 6, is it possible to include more data points to make the black curve smooth? If not, data maker should be added on the black curve.

5.      In Fig. 9, the measured result is based on a wavelength of 677 nm. The reason for selecting this wavelength should be clarified. Also, does the dispersion of glass has any influence on the experiment result?

Author Response

Please find attached the response to the reviewer’s comments.

Author Response File: Author Response.docx