kHz, 10s TW, Femtosecond Source Based on Yb:YAG Thin Disk Laser Pumped OPCPA of Low Quantum Defect
, Xin Liu 1,2,†, Jinhui Li 1,2, Hushan Wang 1,2, Yishan Wang 1,2, Wei Zhao 1,2, Huabao Cao 1,2,* and Yuxi Fu 1,2,*Round 1
Reviewer 1 Report
The authors promote the use of high-energy kHz repetition rate Yb:YAG disk laser for pumping of two and three-stage OPCPA based on LiGaS2 crystal with high conversion efficiency due to the signal wavelength is close to pump. In support of their claim, they put forward the results of numerical simulations. The value of this work would have grown significantly if at least an initial experiment had been presented, although with limited pump energies. Nevertheless, the presented concept is quite interesting and can be published. Could the authors, in this case, give their recommendations for the implementation of even the initial stage of the demonstration experiment: what the seed source is planned or suggested to use here? What methods for spatial and temporal shaping of both signal and pump pulses?
Author Response
Response to Reviewer 1 Comments
Comments to the Author
The authors promote the use of high-energy kHz repetition rate Yb:YAG disk laser for pumping of two and three-stage OPCPA based on LiGaS2 crystal with high conversion efficiency due to the signal wavelength is close to pump. In support of their claim, they put forward the results of numerical simulations. The value of this work would have grown significantly if at least an initial experiment had been presented, although with limited pump energies. Nevertheless, the presented concept is quite interesting and can be published. Could the authors, in this case, give their recommendations for the implementation of even the initial stage of the demonstration experiment: what the seed source is planned or suggested to use here? What methods for spatial and temporal shaping of both signal and pump pulses?
Response: Thank you for your rigorous consideration. For the demonstration experiment, the seed source can be provided by an OPCPA system with broadband signal and high output energy (mentioned on page 3 paragraph 2 in the revised manuscript). The super Gaussian temporal shape of pump pulse can be realized by an acousto-optic pulse shaping (mentioned on page 3 paragraph 3 in the revised manuscript). And that the super Gaussian spatial shape can be obtained by high energy Yb:YAG laser system, for instance, the cryogenic cooled Yb:YAG thin disk lasers demonstrated in colorado state university [13], or beam shaping by a telescope system composed of two aspheric mirrors with initial pump with Gaussian beam profile.
The sentence “The spatial and temporal shapes of pumps are both 6 order super Gaussian. Flat-top beams have already been obtained for cryogenic cooled Yb:YAG thin disk lasers [13, 38], and the super Gaussian temporal shape of the pump can be realized with the help of acousto-optic pulse shaping based on the fact that the pumps are chirped.” has been replaced with “Flat-top beams have already been obtained for cryogenic cooled Yb:YAG thin disk lasers [13, 40]. Flat-top pumps can also be obtained by beam shaping, which has already been demonstrated experimentally [41]. The super Gaussian temporal shape of the pump can be realized with the help of acousto-optic pulse shaping based on the fact that the pumps are chirped.” on page 3 paragraph 3 in the revised manuscript.
And one reference is added in the revised manuscript, which is listed as follows:
- X. Zou, W. Li, S. Qu, K. Liu, H. Li, Q. Wang, Y. Zhang, H. Liang, “Flat-Top Pumped Multi-Millijoule Mid-Infrared Parametric Chirped-Pulse Amplifier at 10 kHz Repetition Rate,” Laser Photonics Rev. 15, 2000292 (2021).
Author Response File: 
Author Response.docx
Reviewer 2 Report
This OPCPA proposal is probably doable. There has been a lot of interest in LGS and also ZGP and Lithium Niobate crystals recently, but mostly because of longer wavelengths. But this is probably not very new. The approach here is to amplify the signal using a 1 micron pump. The paper would be much more interesting if they looked at the amplification of the idler at longer wavelengths, which is the general trend in the field.
I am surprised by the efficiencies that they report, or calculate. The LGS has a transmission of 0.6 in this region. I am surprised by the claim that 60% can be reached with 20fs compression. I would need to be convinced more of this. I suggest that a supplementary document is included with all the actual details of the calculations.
The paper needs a more detailed description of what is already done. What sets it aside from BBO type approaches. Why do this? I do not think this is very new, but possibly with some more power? I am not sure I fully follow how they propose to get this bandwidth for the sub-20fs output.
As it stands this is a manuscript that just presents the numbers they get from the calculation, but needs more explicit work.
Author Response
Response to Reviewer 2 Comments
Comments to the Author
This OPCPA proposal is probably doable. There has been a lot of interest in LGS and also ZGP and Lithium Niobate crystals recently, but mostly because of longer wavelengths. But this is probably not very new. The approach here is to amplify the signal using a 1 micron pump. The paper would be much more interesting if they looked at the amplification of the idler at longer wavelengths, which is the general trend in the field.
Response: We gratefully appreciate for your comment. Mid-infrared ultrashort pulses indeed have attracted great attention because they are useful for many applications of strong-field physics, including THz generation and soft-X ray generation through HHG. However, they are still application appreciate more on peak intensity than the wavelength. For instance, it is interesting for researcher to obtain high flux XUV sources based on driving laser at 1 μm. Meanwhile, the research of the amplification of the idler is also one of works we are studying. Perhaps some progress will be obtained in the future.
Point 1: I am surprised by the efficiencies that they report, or calculate. The LGS has a transmission of 0.6 in this region. I am surprised by the claim that 60% can be reached with 20fs compression. I would need to be convinced more of this. I suggest that a supplementary document is included with all the actual details of the calculations.
Response 1: We greatly appreciate the reviewer for careful reading of our manuscript. The transmission is 0.6 because of the Fresnel reflection on the surfaces. The absorption on the spectral range studied in this manuscript is rather low. One can find it in the Ref. [33].
And two more references are added in the revised manuscript, which are listed as follows:
- L. Isaenko; A. Yelisseyev; S. Lobanov; A. Titov; V. Petrov; J.-J. Zondy; P. Krinitsin; A. Merkulov; V. Vedenyapin; J. Smirnova, “Growth and properties of LiGaX2 (X = S, Se, Te) single crystals for nonlinear optical applications in the mid-IR,” Cryst. Res. Technol. 38, 379–387 (2003).
- M.Namboodiri, C. Luo, G. Indorf, T. Golz, I. Grguraš, J. H. Buss, M. Schulz, R. Riedel, M. J. Prandolini, and T. Laarmann, “Optical properties of Li-based nonlinear crystals for high power mid-IR OPCPA pumped at 1 µm under realistic operational conditions,” Opt. Mater. Express 11, 231-239 (2021).
Point 2: The paper needs a more detailed description of what is already done. What sets it aside from BBO type approaches. Why do this? I do not think this is very new, but possibly with some more power? I am not sure I fully follow how they propose to get this bandwidth for the sub-20fs output.
Response 2: The reviewer is correct that crystals like BBO are excellent choice for OPA to achieve amplification of ultrashort pulses. However, the transmission band of those crystals can not cover the idler, then it will result into heating of the crystals. The transmission curve of BBO is showed below.
Figure 1. The transmission curve of BBO
Point 3: As it stands this is a manuscript that just presents the numbers they get from the calculation, but needs more explicit work.
Response 3: Thank you for your great suggestion. This manuscript is focused on theoretical work. The experimental research is in progress. We hope to present it as soon as possible.
Author Response File: Author Response.docx
