Picosecond Pulsed-Periodic High-Peak Power Nd:YAG Laser Operationally Controlled by KTP-Based Pockels Cell
Round 1
Reviewer 1 Report
The authors suggested a laser scheme to use active-passive mode-locked and negative feedback-controlled master oscillator and regenerative amplifier based on common end-diode-pumped Nd:YAG crystal. By employing double-crystal thermally compensated Pockels cells based on X/Y-cut KTP/RTP crystals, which is essential for the implementation of ultrafast laser systems, they demonstrated stable laser operation with output pulse energy of 1.6 mJ and duration of 25 ps at tunable repetition rates ranging from single shot to 200 Hz. They also measured second and third harmonics efficiencies among different kinds of crystals and found Y-cut KTP crystal giving the best performance. The theoretical and experimental details are kindly provided in the main text. The contents in this manuscript have a significant impact, and this scheme should be very useful for researchers in this field. Therefore, I strongly recommend the publication of this work in Crystals with minor modifications addressing the following comments:
1. Is there an intuitive explanation of the laser operation failure when the rep rate is above 200Hz?
2. How long can the laser stably operate in the laboratory environment? Is the laser sensitive to environment temperature?
3. Please plot and mark the data of Fig 6, Fig 7, and Fig 8 in a clear background instead of the screenshot of the oscilloscope if possible.
4. Remove the text from line 649 to line 652.
Author Response
Response to Reviewer 1 Comments
Dear Reviewer,
Thank you very much for reviewing our manuscript and for your comments.
- Is there an intuitive explanation of the laser operation failure when the rep rate is above 200Hz?
Operation failure at the repetition rate above 200 Hz is mainly attributed to the exit of the oscillator cavity from the region of stability due to an increase in the strength of the thermal lens. It is discussed in the paragraph just before the Figure 7. And we have now added another explanatory sentence in the lines 6-8 from the bottom of the paragraph: “Generation failure at the repetition rates above 200 Hz is mainly attributed to the exit of the oscillator cavity from the region of stability due to an increase in the strength of the thermal lens with the average pump power growth”.
- How long can the laser stably operate in the laboratory environment? Is the laser sensitive to environment temperature?
We have added the sentence: “The laser scheme is very stable and is able to work stably in laboratory environment for many hours, being, however, sensitive to environment temperature fluctuations above ~5 degrees.”
- Please plot and mark the data of Fig 6, Fig 7, and Fig 8 in a clear background instead of the screenshot of the oscilloscope if possible.
We redid the colors in Figures 6,7 and 8 for better visibility
- Remove the text from line 649 to line 652.
We removed the redundant fragment.
Sincerely,
Authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, the authors investigate the picosecond pulse-periodic high-peak-power active-passive mode-locked and negative feedback controlled Nd:YAG master oscillator and the Nd:YAG regenerative amplifier. . The experimental results are also discussed in detail.
1:The introduction is t One aspect that the manuscript focuses on is the y-cut KTP crystal, it is better to put on its advantages.
2: According to the description, the working aperture of KTP is ~2x2 mm2. With a pulse energy of 1.6mJ and a pulse width of 25ps, it is estimated that the peak power density on the KTP crystal should be higher than 2GW/cm2. How to ensure that the crystal is not damaged?
Author Response
Response to Reviewer 2 Comments
Dear Reviewer,
Thank you very much for reviewing our manuscript and for your comments.
1:The introduction is t One aspect that the manuscript focuses on is the y-cut KTP crystal, it is better to put on its advantages.
We have now added in the end of the Abstarct: “The minimal second and third harmonics efficiency levels observed in the Y-cut KTP crystal based Pockels cells seem to be their important advantages”.
Also, the advantages of Y-cut KTP were discussed in the last paragraph of the Introduction, as well as in the Conclusion»
2: According to the description, the working aperture of KTP is ~2x2 mm2. With a pulse energy of 1.6mJ and a pulse width of 25ps, it is estimated that the peak power density on the KTP crystal should be higher than 2GW/cm2. How to ensure that the crystal is not damaged?
Any damage to the KTP-based Pockels cell would irreversibly destroy its proper and stable operation. But please note, that according the scheme, pulses with the energy level of 1.6 mJ are commutated on the regenerative amplification stage by DKDP Pockels cells, while the maximum pulse energy in the KTP based Pockels cell takes place on the oscillator stage and is only 4µJ (please see the penultimate paragraph on the page 14 beginning with the word “comparing”.
Sincerely,
Authors
Author Response File: Author Response.pdf
