Temporal Contrast Enhancement Based on the Self-Diffraction Process with Different Kerr Media

Round 1

Reviewer 1 Report

The manuscript “Temporal contrast enhancement based on self-diffraction process with different Kerr media” investigated experimentally laser temporal contrast enhancement based on non-linear self-diffraction process with different Kerr media. Laser contrast plays crucial role in many laser-plasma interaction aspects, especially in laser-solid interaction in which extensive physical dynamics take in place. Nowadays, as the rapid development of high power laser technologies, multi-PW lasers have been operational worldwide with the unprecedented super high intensity on the order or 10E22-23 W/cm2. In this regime, the pre-pulse intensity with a common temporal contrast of 10E8 is high enough to produce pre-plasmas, which significantly affects the physics of the laser-plasma interaction. Therefore, it’s extremely important to investigate new technologies of improving laser contrast.  

 

This work presents experimental results of contrast enhancement with a new method based on self-diffraction process, demonstrates the generation of high contrast laser pulses on the order of 10e12 with a high conversion efficiency. After studying the manuscript carefully, I found the main results are interesting and technically solid. The manuscript was organized and written very well. The findings and methods in this work is of great interest and importance to both the laser development community and strong field laser-plasma study community. I would recommend it to be published without any hesitation. 

 

The only minor comment is that the language needs to be improved. 

Author Response

Thanks for the positive comments and the suggestion. The English of the whole manuscript has been improved in the paper.

Author Response File: Author Response.docx

Reviewer 2 Report

“Temporal contrast enhancement based on self-diffraction process with different Kerr media”

 

The manuscript addresses a subject of great general importance: high temporal contrast in ultra-intense lasers.

In this regard, the present manuscript reports the enhancement of the temporal contrast by seven orders of magnitude to 10¹² based on self-diffraction process with three different non-linear transparent media: BK7 glasses, Al₂O₃ and CVD diamond. The highest conversion efficiency was achieved in case of Al₂O₃ plate also providing higher output pulse energies.

The results are of great practical interest in the area of ultra-intense and ultra-short pulse lasers but also for other fields.

The manuscript can be accepted, but few changes are required in some points:

 

1.      A comment to relate the chosen non-linear transparent materials should be introduced.

2.      In figure 4b is represented the SD+1 signal intensity distribution in the spatial domain. Please mention for which Kerr medium it was generated.

3.      In figure 5 it would be indicated to denote the propagation direction of the laser beam.

4.      Please check and correct the spelling and grammar. Some inadequate collocations

appeared, like:

-          the cubes that of the incident temporal contrast

-          keeping the Kerr media wouldn’t be damaged

-          a black dot was appeared

-          exist/exit angles

-          etc.

 

or particular words are missing:

 

-          three Kerr media above

-          the spectra of and the input laser pulse

-          etc.

Comments for author File: Comments.pdf

Author Response

The point-by-point response has been attached in the Word file.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript photonics-1912663 reports about a particular temporal contrast enhancement based on a self-diffraction process with different Kerr media including BK7 glasses, AL2O3 and CVD diamonds. Please see below a list of comments to the authors:

1. How is the polarization exhibited by the self-diffracted signal?
2. If possible, please report the absorbance spectra of the samples and ablation threshold of the samples studied.
3. A photo of the experiment would be welcome.
4. Different physical mechanisms can be responsible for the self-diffraction effect. Electronic and thermal contributions can be present in the experiment and fractional calculus can be required to describe phase changes, polarization or self-diffracted irradiance. The authors are invited to discuss about this point and see for instance: https://doi.org/10.1088/1402-4896/ab3ae9
5. It is not clear how were selected the samples studied and the potential applications of the main findings should be confronted with updated publications of this topic. You can see for instance DOI: 10.1088/0256-307X/38/7/074202.
6. How was calibrated the experimental setup? Usually a CS2 sample is employed as a reference.
7. In Figure 5, BS should be rotated 90 degrees in order to illustrate a reflection directed to mirror 3.
8. Please report the noise/signal ration of the self-diffraction process.
9. The collective citations could be better justified if they are described in individual form.
10. The error bar and statistics in experimental results is missing.

Author Response

The point-by-point response to your comments  has been attached to the Word file.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

I appreciate the effort of the authors to improve the presentation of their work. Some of the points have been successfully addressed. However, two fundamental points are still present, please see below:

1. The polarization exhibited by the self-diffracted signal depends on physical mechanism responsible for the optical Kerr effect. Moreover, the polarization of the incident beams is modulated by the induced birefringence represented by the optical Kerr effect. This part was not discussed as previously requested in order to clarify this point. 

4. Different physical mechanisms can be responsible for the self-diffraction effect but the discussion was omitted. Electronic and thermal contributions can be present; but also molecular orientation responsible for the optical Kerr effect and others. The authors did not provide evidence that the physical mechanism is exclusively electronic; they neither provided numerical or experimental evidence of absence of thermal effects that surely can be induced by femtosecond pulses in particular conditions with high repetition rate of irradiation.

Author Response

Thanks for your comments  and the response is in the Word file.

Author Response File: Author Response.docx