Review Reports

Round 1

Reviewer 1 Report

The article presents a comprehensive review of holographic recording and data storage in materials through thermomagnetic recording. The work is well written, coherent, well illustrated with high quality figures.

I have a few minor suggestions that I believe will increase the quality of the publication:

1) Please emphasise the novelty of the review and justify the need for it;

2)equation 1 implies that if the introduced rotation is larger than Pi/2 overmodulation may be observed. Discuss this phenomenon in the context of these particular materials and if this is at all possible.

3) results from the study of the effect of modulation method are presented in page 5. please include a short description of the modulation methods.

4)page 9, line 269 - the equation is not readable

 

Author Response

Thank you for your kind review. I answer your questions and comments as follows.

1) Please emphasise the novelty of the review and justify the need for it;

(A) The following sentence is added to in L65-L69.

“Since magnetic garnet is an oxide, ... that may occur with photopolymers.”

 

2) equation 1 implies that if the introduced rotation is larger than Pi/2 overmodulation may be observed. Discuss this phenomenon in the context of these particular materials and if this is at all possible.

(A) Actually, the rotation angle is less than Pi/2. So, the following description about the rotation angle of magnetic hologram is added in L148-L157.

“Equation (1) shows that ... as deep as possible are desirable.”

 

3) results from the study of the effect of modulation method are presented in page 5. please include a short description of the modulation methods.

(A) I added the description of modulation methods and changed the expression of related texts accordingly in L189-L198. In addition, an example of each modulation scheme is shown in Fig. 5a.

“In addition, readout errors during reconstruction ...”

 

4) page 9, line 269 - the equation is not readable.

(A) To make the equation easier to read, I rewrote the text as follows, in L338-L353.

“In this model, the ratio of thermal diffusivities ... in magnetic layer due to heat diffusion.”

Reviewer 2 Report

The paper is well written and can be recommended for those who are familiar with principles of holography and want to know about magnetic holography. I only suggest minor corrections before the paper is accepted.

 

"... similar to a QR code ..." - I suggest to remove it, because the principle of holography and QR codes are too different and might confuse the reader.

 

When explaining the two schemes shown in Fig. 1, it would help the reader to mention a relation to off-axis and in-line types of holography.

 

The principles of recording and reconstructing magnetic holograms are not clearly explained. Fig. 2 shows only perfect periodic structures, however a real hologram is an interference pattern where fringes are not all of the same period. So, Fig. 2 need to be slightly revised, it need to show a distribution which is more realistic with some aperiodic fringes, and not of all fringes of the same period.

 

It can help the reader to indicate everywhere the size of the used materials and elements. In all figures, the scale bars should be provided and sizes must be indicated.

 

Fig. 7. It is not clear what "1500 line-pairs/mm" means, how does it relate to the period of fringes and why this parameter is important for the efficiency? There is no such parameter in Eq. 1. (b) and (c) it is not clear what is x and y axis in these 2d distributions.

Line 269: The symbols are not shown.

Author Response

Thank you for your kind review. I answer your questions and comments as follows.

1) "... similar to a QR code ..." - I suggest to remove it, because the principle of holography and QR codes are too different and might confuse the reader.

(A) I removed the words “similar to a QR code” as suggested in L36.

 

2) When explaining the two schemes shown in Fig. 1, it would help the reader to mention a relation to off-axis and in-line types of holography.

(A) Thank you for your comment. Of course, there are various types of holography, and it is important to explain off-axis and in-line types of holography. However, the interference methods used for holographic memory are mainly the two methods shown here, so I would like to explain only these two methods to avoid confusion for the reader due to the explanation of many methods. Instead, I modified the text in L38-39 to show that there are many types of holography as well.

“There are various types of holography, but two methods are mainly used as optical interference systems for recording and reconstruction of holographic memory; ...”

 

3) The principles of recording and reconstructing magnetic holograms are not clearly explained. Fig. 2 shows only perfect periodic structures, however a real hologram is an interference pattern where fringes are not all of the same period. So, Fig. 2 need to be slightly revised, it need to show a distribution which is more realistic with some aperiodic fringes, and not of all fringes of the same period.

  (A) Figure 2 was revised to show aperiodic fringes.

 

4) It can help the reader to indicate everywhere the size of the used materials and elements. In all figures, the scale bars should be provided and sizes must be indicated.

(A) Probably you mentioned about the reconstruction images of magnetic hologram in Fig. 4 through Fig. 6 and Fig. 10. These are images from a CCD camera, so the size of the image has no real meaning. However, how many pixels the image contains is important, so the descriptions of pixel sizes of signal pattern were added in Fig. 5(a) and Fig. 10(c). On the other hand, scales are needed in Fig. 7b, so scales were added in Fig. 7b. Figure 7c also needs scale, but since the lengths of magnetic fringe are already shown in the figure, the scale is not added.

 

5) Fig. 7. It is not clear what "1500 line-pairs/mm" means, how does it relate to the period of fringes and why this parameter is important for the efficiency? There is no such parameter in Eq. 1. (b) and (c) it is not clear what is x and y axis in these 2d distributions.

(A) I am sorry for the incomprehensible description. The meaning and importance of “1500 line-pair/mm” are added in Section 2 in L93-L103 and in L163-L169. In addition, to make the meaning of Fig. 7b easier to understand, the names of each part (air, etc.) have been added to the figure, and the text has been slightly revised in L251-L253 and in L261-263.

In L93-L103 “the effect of period of interference fringe ... using the high energy and short pulse laser.”

In L163-L169 “Nakamura et al. [26] reported that ... deep magnetic fringe from eq. (1).”

In L251-253 “To see the effect of recording energy ... are shown in Fig. 7. As shown in Fig. 7a, ...”

In L261-263 “Figure 7b shows the calculated temperature change around ...”

 

6) Line 269: The symbols are not shown.

(A) To make the equation easier to read, I rewrote the text as follows, in L338-L353.

“In this model, the ratio of thermal diffusivities ... in magnetic layer due to heat diffusion.”

Reviewer 3 Report

In this article the author reviews the principles of magnetic holograms and applications of them to the fabrication of holographic memories.

In this article the authors reviews the general methods to obtain magnetic holograms, namely thermomagnetic recording and reconstruction using the principles and of magneto-optical effect. I have found that the review has been performed in a way easy to understand, with simple explanations without complex derivations, and thus the article is easy to follow.

The number of citations is also sufficient to guarantee that an exhaustive search in the literature has been made. The author has also reviewed its own work and as she/he says in the article she/he has proposed the insertion of heat dissipation (HD) layers to enhance the deepness of the magnetic fringes recorded. For me the article is technically correct and it is well written. The principles of magnetic holograms are well explained, so the article could serve as a complete guide for researchers working in the field. Therefore I recommend the article for publication.

I have only one doubt:

The author says in the text that he proposes the introduction of heat dissipation layers. From reading the text (the abstract and the introduction) it seems that this proposal is made in this work, but the author (in the last section) mentions some articles on the subject written by himself, so it is not clear that the last discussion (before the conclusions) and the experiments presented are really made for this particular work or are also a revision of his proper work. I suggest that this must be clarified.

Author Response

(A) Thank you for your comment. To make it clear that this article reviews the past papers, I started the paragraph in each section on HDL with the author name of the cited references, and modified the relevant text including abstract accordingly. In addition, A sentence was added to the abstract to emphasize the importance of deep holograms as a need for HDL media.

In L8-L11 “To achieve bright reconstruction image, ... using transparent magnetic garnets as a recording material.”

In L14 “It was found that this HD multilayer medium ...”

In L286-287 “Isogai et al. [30] and Nakamura et al. [33-35] proposed multilayer media in which ...”

In L295-296 “Isogai et al. [30] proposed that the optical thickness ...”

In L313-316 “since the thickness of the magnetic layer ... with numerical simulation.”

In L336-338 “To determine the thickness of each layer in the HD multilayer medium, Nakamura et al. [34, 35] proposed ...”

In L359-363 “Based on this simple model, Nakamura et al. [34, 35] ... in HDL into Bi:RIG. “