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Abstract
We numerically demonstrate highly efficient mid-infrared quasi-parametric chirped-pulse amplification (QPCPA) based on a recently developed Sm3+-doped La3Ga5.5Nb0.5O14 (Sm:LGN) crystal. At pump wavelength around 1 µm, the broadband absorption of Sm3+ on idler pulses can enable QPCPA for femtosecond signal pulses centered at 3.5 or 5 µm, with a conversion efficiency approaching the quantum limit. Due to suppression of back conversion, such mid-infrared QPCPA exhibits robustness against phase-mismatch and pump-intensity variation. The Sm:LGN-based QPCPA will provide an efficient approach for converting currently well-developed intense laser pulses at 1 µm to mid-infrared ultrashort pulses.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Quasi-parametric chirped-pulse amplification (QPCPA) is an idler-dissipated nonlinear three-wave mixing process with strong pump depletion and high signal efficiency [1–3]. The naming of “quasi-parametric” is based on its combination of the parametric attribute in the small-signal regime and the non-parametric attribute in the saturated regime. From the frame of quantum mechanics, the QPCPA belongs to a non-Hermitian optical system with simultaneous gain and losses [4,5]. By the aid of a Sm3+-doped YCa4O(BO3)3 (Sm:YCOB) crystal, the QPCPA concept has been experimental validated in the near-infrared region [1], where the doped Sm3+ ions impose losses on idler (1550 nm) but not on pump (532 nm) and signal (810 nm). Ultrahigh pump depletion of 85% has been achieved in the Sm:YCOB-based QPCPA [3], with signal efficiency far exceeding its counterpart of optical parametric chirped-pulse amplification (OPCPA). In this paper, we extend QPCPA from the near-infrared—where it was previously demonstrated—to the mid-infrared (mid-IR) spectral range, based on a newly developed Sm3+-doped La3Ga5.5Nb0.5O14 (Sm:LGN) crystal [6], and apply it to solve the inefficiency issue confronted by current mid-IR OPCPA systems.
Mid-IR laser pulses have attracted increasing attention due to their potential applications in spectroscopy, sensing, medical treatment, and strong-field physics [7]. Particularly, the high-order harmonic generation processes for attosecond pulses have been greatly promoted by mid-IR driving sources because the ponderomotive energy of an electron in the laser field is proportional to the square of the driving laser wavelength [8,9]. In the absence of suitable laser gain media, the nonlinear OPCPA has been the workhorse to produce strong coherent radiation in the mid-IR range. Table 1 lists the specifications of twelve reported mid-IR OPCPA systems across a range of 2–9 µm [10–22]. Clearly, the real pump-to-signal conversion efficiencies of all these systems are much lower than the theoretical quantum-limited efficiencies. Although the inefficiency is a common issue for all OPCPA systems, it is more significant in the mid-IR range owing to the larger quantum defect. The root cause for this inefficiency is the cyclic dynamic of OPCPA [23]. Unlike lasers, the OPCPA is followed by a back conversion process, which occurs out of order across the bell-shaped spatial and temporal profiles of a pump pulse and makes uniform pump depletion impractical. Complicated shaping on pump or seed pulses can be used to enhance the efficiency before back conversion occurs, but without changing the cyclic nature of OPCPA [14,24,25]. The cyclic dynamic can be broken by introducing losses on idler pulses, which can switch the operation of OPCPA from Hermitian to non-Hermitian regime for enhancing the signal efficiency. Several methods for dissipating idler have been proposed such as absorption from doping rare-earth ions (i.e., the QPCPA) [1–3] or using infrared absorption edge of a material [26], block by coating [27], large-angle walk-off [28], and cascaded second-harmonic generation process [29]. With idler dissipation, efficient signal amplification can be achieved even in the absence of phase matching [30–32].
Table 1. Experimental conditions and conversion efficiencies of reported mid-IR OPCPA systems
To facilitate the application of QPCPA in the mid-IR spectral range, a new material of Sm:LGN was developed by doping Sm3+ into oxide La3Ga5.5Nb0.5O14 (LGN) [6]. The pure LGN crystal exhibits high transmission in 0.5–6.0 µm [33], and the absorption spectrum of Sm3+ can enable broadband QPCPA at the central wavelength of 3.5 or 5 µm when pumped at 1030 nm. Similar to the Sm:YCOB crystal, the Sm:LGN crystal can be grown into a large size by the Czochralski method, which is crucial for the energy scalability. More attractively, the LGN (including Sm:LGN) crystal allows the direct seeding of mid-IR pulses in a noncollinear configuration and thereby enables broadband amplification without suffering from angular dispersion [34]. Here, we will demonstrate the high-efficiency and robustness of the Sm:LGN-based mid-IR QPCPA through a numerical experiment. This work could have implications for mid-IR ultrafast laser, high-field light-matter interaction and non-Hermitian optics.
2. Principal and design
2.1 Modeling of mid-IR QPCPA based on Sm:LGN crystal
The cyclic dynamic of OPCPA manifests as the alternate forward and backward conversions. The forward conversion refers to the down conversion of pump (angular frequency ωp, wave-vector kp), which not only amplifies the seeded signal (angular frequency ωs, wave-vector ks) but also produces the idler (angular frequency ωi = ωp – ωs, wave-vector ki); and the backward conversion occurs once the pump is completely depleted (in the perfect phase-matching condition, Δk = kp – ks – ki = 0), with the energy flowing back to the pump from the signal and idler. For the pulsed pump, the intensity-dependent back conversion occurs out of order across the beam and pulse profiles, so the overall conversion efficiency is much lower than the theoretical limit of ωs/ωp. The conversion efficiency will be further degraded under practical non-perfect phase matching environment, which leads to the advance occurrence of back conversion before the full depletion of pump at individual coordinate. In addition, it is more difficult for mid-IR OPCPA to achieve high efficiency due to the lower theoretical limit of ωs/ωp. As a result, the actual efficiencies of mid-IR OPCPA systems are only a few percent (Table 1).
To enhance the signal efficiency, the idea of QPCPA is to stop the back conversion by dissipating the idler. The doping of rare-earth ions with resonance absorption on the idler waveband is a robust way to introduce losses on idler pulses while keeping broadband amplification for signal pulses. As shown in Fig. 1(a), the nonlinear crystal for QPCPA should combine quadratic nonlinearity for three-wave mixing and strong linear absorption on idler. In the past few years, the Sm:YCOB crystal has been developed for supporting QPCPA pumped at 532 nm and seeded at 810 nm, with the generated idler at 1550 nm lying in the absorption spectral range of Sm3+ [1,3]. If using pump around 1 µm, the signal wavelength can be extended into the mid-IR spectral range with the same absorption spectrum of Sm3+, which unfortunately will be hampered by the limited infrared transparent range of YCOB. Thus, the YCOB has to be replaced by a new material of a better IR transmission. The positive uniaxial LGN crystal is a qualified candidate, which has an extended IR transmission cutoff wavelength at 7.4 µm [red and black curves in Fig. 1(b)], a large size scalability (up to 60 mm in diameter [35]), a high damage threshold (2.8 GW/cm2 at 1.064 µm, 5 ns and 10 Hz [36]) and a large effective nonlinear coefficient (d11 = 2.9 pm/V [36]). The combination of Sm3+ ions and LGN can offer a new QPCPA crystal, Sm:LGN, which has been grown successfully [6]. Figures 1(b) and 1(c) plot the transmission spectra and absorption spectra, respectively, for pure LGN crystals grown by two research groups (red and black curves), 10%-Sm3+-doped (blue curve) and 20%-Sm3+-doped (green curve) Sm:LGN crystals. The Sm:LGN crystal provides strong absorption in the range of 1.1–1.7 µm but highly transmits the pump at 1030 nm. In the mid-IR spectral region, there also appears observable absorption peaks around 1.9, 2.6 and 4.1 µm, resulting from the Sm3+ doping. As QPCPA requires strong idler absorption and weak signal absorption simultaneously, the Sm:LGN crystal can support QPCPA only at two separated wavebands around 3.5 and 5 µm, respectively.
Fig. 1. Principle of mid-IR QPCPA based on Sm:LGN. (a) Schematic diagram of the mid-IR QPCPA process. The seeded mid-IR pulses intersect with the pump pulses by an angle α, and the generated idler pulses are dissipated by the doped Sm3+ ions. The solid (dashed) line represents the real (virtual) energy level. (b) Transmission spectra of 1-mm-thick uncoated LGN and Sm:LGN crystals. Red (black) curve, a LGN crystal with data from Ref. 35 (Ref. 6). Blue (green) curve, a 10% (20%)-Sm3+-doped LGN crystal with data from Ref. 6. (c) Calculated absorption spectra from the transmittance spectra in Fig. 1(b) after eliminating the Fresnel reflection loss on the two surfaces.
Another important consideration to the mid-IR QPCPA is the phase-matching characteristic. As the lack of precise Sellmeier equation for the Sm:LGN crystal, the Sellmeier equations of LGN crystal are used in following evaluations [33], which will not cause significant difference on the output results from our previous experience on the use of Sm:YCOB crystal [3]. Although the Sm3+ ions doping can change the refractive indexes, it is expected that the dispersion characteristic of a low-doping (≤30%) Sm:LGN crystal will not derivate much from that of a pure LGN crystal. In other words, the low Sm3+-ions doping for imposing idler absorption has only a limited effect on the broadband phase matching conditions of LGN crystal. Therefore, it is reasonable to evaluate the Sm:LGN-based QPCPA according to the Sellmeier equations of LGN crystal. To ensure a broad gain bandwidth for mid-IR ultrashort pulses, a noncollinear geometry for group-velocity matching should be supported. With 1030-nm pump, the noncollinear solutions for the Sm:LGN crystals can be found in both Type-I (op → es + ei) and Type-II (op → es + oi) configurations. The Type-II solutions exist in a range of 4.4–5.5 µm, while the Type-I solutions exist in a broader range of 2.2–5.5 µm. For the 5-µm QPCPA, the noncollinear angle α (refers to the angle between kp and ks) is 8.99° in the Type-I case and 5.07° in the Type-II case, so the Type-II solution is better due to the smaller noncollinear angle. For the 3.5-µm QPCPA, only Type-I solution exits with a noncollinear angle α of 4.33°. Note that, all these noncollinear solutions are based on the direct seeding of mid-IR pulses. This is important for ensuing the beam quality of the mid-IR pulses; otherwise, angular dispersion will be added on the mid-IR pulses if they are generated as the idler in the noncollinear geometry. Some reported mid-IR OPCPA systems adopted near-IR seeding and generated mid-IR pulses as idler, in which collinear geometries had to be used to avoid angular dispersion on the mid-IR idler, as shown in Table 1. The needed broadband mid-IR seeds at 3.5 or 5 µm can be readily generated by intrapulse difference generation pumped by 800-nm few cycle pulses [37,38]. Therefore, it is feasible to build a mid-IR QPCPA based on Sm:LGN crystal. In the following text, we focus on the simulation of a 5-µm QPCPA.
2.2 Numerical code
The simulations for mid-IR QPCPA are based on the nonlinear coupled-wave equations derived under the slowly varying envelop approximation [39], including the effects of absorption (γj), dispersion (βmj=∂(m)kj/∂ω(m)), walk-off (ρj), diffraction and nonlinear refractive (n2j).
Table 2. Input parameters in the 5-µm QPCPA simulations
3. Simulation results
We conduct numerical simulations for a 1030-nm pumped QPCPA based on a Sm:LGN crystal. In sections 3.1 and 3.2, the efficiency and robustness are studied for a 5-µm QPCPA under a Type-II phase matching condition owing to a larger effective coefficient and a smaller noncollinear angle (Table 2). For comparison, the results of OPCPA (γi = 0) are also simulated under the same input parameters.
3.1 High efficiency close to the theoretical limit
Figure 2(a) presents the simulated conversion efficiencies for the 5-µm QPCPA (γi ≠ 0) and OPCPA (γi = 0). The OPCPA efficiency reaches 9% at L = 1.18 cm and then decreases to 6.5% at L = 1.8 cm. Within the widely-adopted operation range around L = 1.18 cm, the OPCPA efficiency is far below the theoretical maximum of 20% (dashed line in Fig. 2). With further evolution beyond L = 1.8 cm, the OPCPA efficiency rises in volatility due to the cascaded process of forward and backward conversions. Once the idler absorption is added, the amplification behaviors change significantly. The back conversion can be suppressed by the idler absorption. The efficiency of QPCPA with γi = 2 /cm keeps increasing within the crystal, and reaches to 19% at L = 6 cm. Such a high efficiency has been close to theoretical limit, beyond two times of the OPCPA efficiency at L = 1.18 cm. The high efficiency maintains when the idler absorption varies in the range of 1–4 /cm, which slightly degrades with the idler absorption. The increase of idler absorption decreases the small-signal gain, as shown by the curve slopes between L = 0.5 to 1 cm. However, no matter how large the idler absorption is, the efficiency can climb to the theoretical limit if the crystal is long enough. Assuming a crystal size of 30 × 30 mm2 (below the achievable maximum crystal size), the allowable pump power is approximately 350 GW at the pump intensity of 50 GW/cm2. Under the ultrahigh conversion efficiency of 19% from 1 to 5 µm, the peak power for the 5-µm signal pulse can reach 65 GW.
Fig. 2. Conversion efficiency of mid-IR QPCPA. (a) Efficiency evolutions under different idler absorption γi. γi = 0 indicates an OPCPA process. (b) Effect of signal absorption γs on the conversion efficiency of the QPCPA with γi = 2 /cm. Dashed lines show the quantum-limited efficiency. See Table 2 for detailed simulation parameters.
As plotted in Fig. 2(a), the idler absorption is indispensable to a high signal efficiency. In fact, a high QPCPA efficiency also requires a smallest possible signal absorption. Figure 2(b) exhibits the effect of signal absorption γs on the QPCPA efficiency (γi = 2 /cm). At γs = 1 /m, the signal efficiency decreases from original 19% down to 17%, and further decreases with the increase of γs. At γs = 4 /m, the signal efficiency no longer keeps increasing with the crystal length L, but begins to drop from L = 4 cm. Considering that the imposed signal absorption is lower than the idler absorption by two orders of magnitude, we can conclude that the QPCPA efficiency is more sensitive to the signal absorption. It is understandable because the nonlinear coupling strength in the saturated regime of QPCPA (both pump and idler are depleted) is mainly determined by the signal intensity. Therefore, lowering the signal absorption within the nonlinear crystal is essential to ensure the high QPCPA efficiency, which puts forward high requirements on the quality control in the growth of Sm:LGN crystal. From this perspective, it is not suitable to build QPCPA around the signal wavelength of 1.9, 2.6 and 4.1 µm, where the signal absorption is too high to support the high efficiency [Fig. 1(c)].
The difference between the amplification behaviors of QPCPA and OPCPA can be better reflected in the spectral domain. Figure 3 shows the evolutions of mid-IR spectrum within the crystals. For OPCPA [Fig. 3(a)], the spectral component at 5 µm reaches saturation first at L = 0.85 cm and then drops due to back conversion, while the evolution of other spectral components lags due to weaker pump and/or larger phase mismatch. Therefore, there appears a dip on the output mid-IR spectrum. Due to the out-of-order evolution of different spectral components, the crystal position of the highest spectral intensity at 5 µm (L = 0.85 cm) does not coincide with that of the highest overall energy (L = 1.18 cm). The compressed pulse profiles at L = 0.85 and 1.18 cm are also given in Fig. 3(a), where the pulse duration at L = 1.18 cm is shorter due to the broader spectral bandwidth. The pulse duration can be shortened with the further increase of the crystal; however, the efficiency degrades as well. Such a trade-off between the conversion efficiency and gain bandwidth has to be considered in the design of OPCPA [23]. The QPCPA exhibits a quite different spectral evolution behavior with the OPCPA, as shown in Fig. 3(b). All mid-IR spectral components can reach the maximums without back conversions. As a result, the spectrum broadens with amplification, breaking the trade-off between efficiency and bandwidth. At the exit end of the crystal, the temporal profile of the chirped mid-IR signal is almost the same as that of the pump, a result of near complete pump depletion. The compressed pulse duration shortens with amplification and is down to 75 fs finally. Such a pulse duration is nearly the same as that of OPCPA at the highest efficiency.
Fig. 3. Mid-IR spectrum evolutions along the crystal in (a) OPCPA with γi = 0 and (b) QPCPA with γi = 2 /cm. In (a), two Fourier-transform-limited pulses are inset for the spectra at L = 0.85 (left) and 1.18 cm (right), respectively. In (b), two Fourier-transform-limited pulses are inset for the spectra at L = 1 (left) and 6 cm (right), respectively.
The output beam profiles of QPCPA and OPCPA are given in Fig. 4. For OPCPA at L = 1.18 cm, only the center of pump beam is effectively depleted [Fig. 4(a)] and converted to the mid-IR beam [Fig. 4(b)]. By contrast, the pump in QPCPA is almost fully depleted [Fig. 4(d)], and the generated mid-IR beam [Fig. 4(e)] has a higher central intensity and a larger beam size than that in OPCPA [Fig. 4(b)]. After focusing by a convex lens with a focal length of 1 m, the mid-IR pulse from QPCPA [Fig. 4(f)] has a smaller beam size and a higher focal intensity than that from OPCPA [Fig. 4(c)]. The large crystal size of the Sm:LGN crystals can support the high peak-power output of mid-IR pulses [40].
Fig. 4. Output beam profiles of the pump and signal pulses from OPCPA with γi = 0 [(a)-(c)] and QPCPA with γi = 2 /cm [(d)-(f)]. (a) [(d)], output pump beam profile from OPCPA (QPCPA). (b) [(e)], near-field beam profile of the amplified mid-IR signal from OPCPA (QPCPA). (c) [(f)], far-field beam profile of the amplified mid-IR signal from OPCPA (QPCPA). A lens with a focal length of 1 m was assumed in the transformation from near field to far field. The crystal length for OPCPA and QPCPA are 1.18 and 6 cm, respectively.
3.2 Robustness against phase mismatch and pump intensity
The simulations shown in Section 3.1 reveal the high efficiency of QPCPA. Due to the obstruction of back conversion, such a high efficiency will not be deteriorated even when some input parameters variate, e.g., the phase mismatch ΔkL at central wavelength [ Fig. 5(a)] and the pump intensity [Fig. 5(b)]. When the ΔkL changes from 0 to 4π, the QPCPA efficiency slightly drops from 19% to 17.3%, while the OPCPA efficiency significant drops from 9% to 0.1%. This means that the QPCPA is insensitive to the drifts of crystal temperature and pump pointing, both of which are helpful for the long-term stability of the system. In high-power OPCPA, the crystal will be heated by light absorption, and the consequent thermal dephasing effect will degrade the conversion efficiency [41]. It seems that the thermal dephasing effect is more severe for QPCPA due to the additional strong idler absorption. In fact, the demonstrated robustness of QPCPA against phase-mismatch can cancel the increased thermal dephasing effect by the idler absorption [42]. Therefore, a high average power can be still expected for the mid-IR QPCPA in the premise of a good heat management to avoid the thermal cracking of nonlinear crystal. In above simulations, the pump intensity is fixed at 50 GW/cm2 for both QPCPA and OPCPA. To reveal the effect of pump intensity on conversion efficiency, here the pump intensity is changed from 10 to 90 GW/cm2 without considering the damage issue. For OPCPA with L = 1.18 cm, the efficiency is optimal at the pump intensity of 50 GW/cm2 and degrades when the pump intensity deviates from this preset value. At the pump intensity of 10 GW/cm2, the OPCPA is no longer efficient. Differently, the QPCPA efficiency shows less sensitivity to the pump intensity. A higher pump intensity always contributes to a higher signal efficiency in QPCPA. At the pump intensity of 10 GW/cm2, the QPCPA still supports an efficiency of ∼12%, exceeding the highest efficiency of OPCPA. When the pump intensity increases to 90 GW/cm2, the conversion efficiency reaches the theoretical limit of 20%, meaning that the pump energy is completely depleted now. The robustness against phase mismatch and pump intensity allows the stable operation of QPCPA, similar as a non-parametric laser amplifier.
Fig. 5. Robustness of the QPCPA scheme. (a) Conversion efficiency versus phase mismatch at central wavelength for QPCPA (red) and OPCPA (black); (b) Conversion efficiency versus pump intensity for QPCPA (red) and OPCPA (black). The dashed lines show the quantum-limited efficiency.
4. Conclusion
In summary, we have prompted the QPCPA scheme into the mid-IR spectral region by the aid of a Sm:LGN crystal. The simultaneous requirement on strong idler absorption and negligible signal absorption determines the operation of QPCPA in two separated spectral regions around 3.5 and 5 µm. Through numerical simulation, we have demonstrated the high efficiency of the mid-IR QPCPA and the resulted good spatial and spectral qualities of the mid-IR pulses. The robustness of mid-IR QPCPA against both phase mismatch and pump intensity allow it maintaining efficient conversion even under a significant change of the running environment. In particular, the 5 µm pulses can be directly output from the 1-µm pumped QPCPA, which, however, can be only produced from the non-oxide ZnGeP2 crystals pumped by 2-µm sources. The Sm:LGN-based QPCPA not only solves the inefficiency issue suffered by current mid-IR OPCPA systems but also provides a new route to produce mid-IR pulses from the mature 1-µm pump sources.
Funding
National Natural Science Foundation of China (62122049, 91850203, 61975120); Shanghai Rising-Star Program (21QA1404600).
Acknowledgments
We acknowledge Libin Yin and Kainan Xiong from Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China, and Dazhi Lu from Shandong University, Jinan, China, for supporting the transmission spectra of Sm:LGN and LGN crystals. Jingui Ma would like to thank the sponsorship of the Yangyang Development Fund.
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. J. Ma, J. Wang, P. Yuan, G. Xie, K. Xiong, Y. Tu, X. Tu, E. Shi, Y. Zheng, and L. Qian, “Quasi-parametric amplification of chirped pulses based on a Sm3+-doped yttrium calcium oxyborate crystal,” Optica 2(11), 1006–1009 (2015). [CrossRef]
2. J. Ma, J. Wang, B. Zhou, P. Yuan, G. Xie, K. Xiong, Y. Zheng, H. Zhu, and L. Qian, “Broadband, efficient, and robust quasi-parametric chirped-pulse amplification,” Opt. Express 25(21), 25149–25164 (2017). [CrossRef]
3. J. Ma, K. Xiong, P. Yuan, X. Tu, J. Wang, G. Xie, Y. Zheng, and L. Qian, “Demonstration of 85% pump depletion and 10-6 noise content in quasi-parametric chirped-pulse amplification,” Light: Sci. Appl. 11(1), 269 (2022). [CrossRef]
4. R. El-Ganainy, M. Khajavikhan, D. N. Christodoulides, and S. K. Ozdemir, “The dawn of non-Hermitian optics,” Commun. Phys. 2(1), 37 (2019). [CrossRef]
5. A. M. Perego, S. K. Turitsyn, and K. Staliunas, “Gain through losses in nonlinear optics,” Light: Sci. Appl. 7(1), 43 (2018). [CrossRef]
6. L. Yin, S. Wang, K. Xiong, X. Tu, J. Xu, Y. Zheng, and E. Shi, “Bridgman growth of new nonlinear optical crystal (La1−xSmx)3Ga5.5Nb0.5O14 for quasi-parametric chirped pulse amplification,” Crystals 9(11), 587 (2019). [CrossRef]
7. M. Ebrahim-Zadeh and I. T. Sorokina, Mid-infrared Coherent Sources and Applications (Springer, 2008).
8. K. Midorikawa, “Progress on table-top isolated attosecond light sources,” Nat. Photonics 16(4), 267–278 (2022). [CrossRef]
9. T. Popmintchev, M-C Chen, D. Popmintchev, et al., “Bright coherent ultrahigh harmonics in the keV X-ray regime from mid-IR femtosecond lasers,” Science 336(6086), 1287–1291 (2012). [CrossRef]
10. K. H. Hong, C. J. Lai, J. P. Siqueira, P. Krogen, J. Moses, C. L. Chang, G. J. Stein, L. E. Zapata, and F. X. Kärtner, “Multi-mJ, kHz, 2.1 µm optical parametric chirped-pulse amplifier and high-flux soft x-ray high-harmonic generation,” Opt. Lett. 39(11), 3145–3148 (2014). [CrossRef]
11. Y. Deng, A. Schwarz, H. Fattahi, M. Ueffing, X. Gu, M. Ossiander, T. Metzger, V. Pervak, H. Ishizuki, T. Taira, T. Kobayashi, G. Marcus, F. Krausz, R. Kienberger, and N. Karpowicz, “Carrier-envelope-phase-stable, 1.2 mJ, 1.5 cycle laser pulses at 2.1 µm,” Opt. Lett. 37(23), 4973–4975 (2012). [CrossRef]
12. G. M. Archipovaite, S. Petit, J. C. Delagnes, and E. Cormier, “100 kHz Yb-fiber laser pumped 3 µm optical parametric amplifier for probing solid-state systems in the strong field regime,” Opt. Lett. 42(5), 891–894 (2017). [CrossRef]
13. J. Alves, H. Pires, C. P. João, and G. Figueira, “Multi-mJ Scaling of 5-Optical Cycle, 3 µm OPCPA,” Photonics 8(11), 503 (2021). [CrossRef]
14. X. Zou, W. Li, S. Qu, K. Liu, H. Li, Q. J. Wang, Y. Zhang, and H. Liang, “Flat-Top Pumped Multi-Millijoule Mid-Infrared Parametric Chirped-Pulse Amplifier at 10 kHz Repetition Rate,” Laser Photonics Rev. 15(6), 2000292 (2021). [CrossRef]
15. N. Thiré, R. Maksimenka, B. Kiss, C. Ferchaud, G. Gitzinger, T. Pinoteau, H. Jousselin, S. Jarosch, P. Bizouard, V. D. Pietro, E. Cormier, K. Osvay, and N. Forget, “Highly stable, 15 W, few-cycle, 65 mrad CEP-noise mid-IR OPCPA for statistical physics,” Opt. Express 26(21), 26907–26915 (2018). [CrossRef]
16. B. W. Mayer, C. R. Phillips, L. Gallmann, and U. Keller, “Mid-infrared pulse generation via achromatic quasi-phase-matched OPCPA,” Opt. Express 22(17), 20798–20808 (2014). [CrossRef]
17. G. Andriukaitis, T. Balčiūnas, S. Ališauskas, A. Pugžlys, A. Baltuška, T. Popmintchev, M. C. Chen, M. M. Murnane, and H. C. Kapteyn, “90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier,” Opt. Lett. 36(15), 2755–2757 (2011). [CrossRef]
18. P. Wang, Y. Li, W. Li, H. Su, B. Shao, S. Li, C. Wang, D. Wang, R. Zhao, Y. Peng, Y. Leng, R. Li, and Z. Xu, “2.6 mJ/100 Hz CEP-stable near-single-cycle 4 µm laser based on OPCPA and hollow-core fiber compression,” Opt. Lett. 43(9), 2197–2200 (2018). [CrossRef]
19. L. Grafenstein, M. Bock, D. Ueberschaer, K. Zawilski, P. Schunemann, U. Griebner, and T. Elsaesser, “5 µm few-cycle pulses with multi-gigawatt peak power at a 1 kHz repetition rate,” Opt. Lett. 42(19), 3796–3799 (2017). [CrossRef]
20. T. Kanai, P. Malevich, S. S. Kangaparambil, K. Ishida, M. Mizui, K. Yamanouchi, H. Hoogland, R. Holzwarth, A. Pugzlys, and A. Baltuska, “Parametric amplification of 100 fs mid-infrared pulses in ZnGeP2 driven by a Ho:YAG chirped-pulse amplifier,” Opt. Lett. 42(4), 683–686 (2017). [CrossRef]
21. U. Elu, T. Steinle, D. Sánchez, L. Maidment, K. Zawilski, P. Schunemann, U. D. Zeitner, C. Simon-Boisson, and J. Biegert, “Table-top high-energy 7 µm OPCPA and 260 mJ Ho: YLF pump laser,” Opt. Lett. 44(13), 3194–3197 (2019). [CrossRef]
22. S. Qu, H. Liang, K. Liu, X. Zou, W. Li, Q. J. Wang, and Y. Zhang, “9 µm few-cycle optical parametric chirped-pulse amplifier based on LiGaS2,” Opt. Lett. 44(10), 2422–2425 (2019). [CrossRef]
23. J. Moses, C. Manzoni, S.-W. Huang, G. Cerullo, and F. X. Kärtner, “Temporal optimization of ultrabroadband high-energy OPCPA,” Opt. Express 17(7), 5540–5555 (2009). [CrossRef]
24. P. Fischer, A. Muschet, T. Lang, R. Salh, and L. Veisz, “Saturation control of an optical parametric chirped-pulse amplifier,” Opt. Express 29(3), 4210–4218 (2021). [CrossRef]
25. J. Moses and S.-W. Huang, “Conformal profile theory for performance scaling of ultrabroadband optical parametric chirped pulse amplification,” J. Opt. Soc. Am. B 28(4), 812–831 (2011). [CrossRef]
26. G. Valiulis and A. Varanavičius, “Numerical study of absorption-enhanced parametric amplification,” Opt. Express 30(9), 15073–15084 (2022). [CrossRef]
27. H. Cao, S. Tóth, M. Kalashnikov, V. Chvykov, and K. Osvay, “Highly efficient, cascaded extraction optical parametric amplifier,” Opt. Express 26(6), 7516–7527 (2018). [CrossRef]
28. Y. Li, H. Zhong, J. Yang, S. Wang, and D. Fan, “Versatile backconversion-inhibited broadband optical parametric amplification based on an idler-separated QPM configuration,” Opt. Lett. 42(14), 2806–2809 (2017). [CrossRef]
29. N. Flemens, N. Swenson, and J. Moses, “Efficient parametric amplification via simultaneous second harmonic generation,” Opt. Express 29(19), 30590–30609 (2021). [CrossRef]
30. R. El-Ganainy, J. I. Dadap, and R. M. O. Jr, “Optical parametric amplification via non-Hermitian phase-matching,” Opt. Lett. 40(21), 5086–5088 (2015). [CrossRef]
31. Q. Zhong, A. Ahmed, J. I. Dadap, R. M. O. Jr, and R. El-Ganainy, “Parametric amplification in quasi-PT symmetric coupled waveguide structures,” New J. Phys. 18(12), 125006 (2016). [CrossRef]
32. A. Ahmed, X. Meng, O. Zhong, R. El-Ganainy, R. M. O. Jr, and J. I. Dadap, “On-chip non-Hermitian optical parametric amplifier with a large bandwidth,” J. Opt. Soc. Am. B 38(7), 2160–2167 (2021). [CrossRef]
33. D. Lu, T. Xu, H. Yu, Q. Fu, H. Zhang, P. Segonds, B. Boulanger, X. Zhang, and J. Wang, “Acentric langanite La3Ga5.5Nb0.5O14 crystal: a new nonlinear crystal for the generation of mid-infrared parametric light,” Opt. Express 24(16), 17603–17615 (2016). [CrossRef]
34. J. Ma, J. Wang, D. Hu, P. Yuan, G. Xie, H. Zhu, H. Yu, H. Zhang, J. Wang, and L. Qian, “Theoretical investigations of broadband mid-infrared optical parametric amplification based on a La3Ga5.5Nb0.5O14 crystal,” Opt. Express 24(21), 23957–23968 (2016). [CrossRef]
35. Y. Wang, J. Liu, C. Cui, F. Liang, D. Lu, J. Wang, J. Ma, H. Zhang, G. Xie, and H. Yu, “Recent progress on acentric La3Nb0.5Ga5.5O14 crystals: large-size growth and application to ultrafast mid-infrared laser systems,” Opt. Mater. Express 12(3), 863–875 (2022). [CrossRef]
36. F. Guo, D. Lu, P. Segonds, J. Debray, H. Yu, H. Zhang, J. Wang, and B. Boulanger, “Phase-matching properties and refined Sellmeier equations of La3Ga5.5Nb0.5O14,” Opt. Mater. Express 8(4), 858–864 (2018). [CrossRef]
37. J. Liu, J. Ma, D. Lu, X. Gu, Z. Cui, P. Yuan, J. Wang, G. Xie, H. Yu, H. Zhang, and L. Qian, “Few-cycle pulses tunable from 3 to 7 µm via intrapulse difference-frequency generation in oxide LGN crystals,” Opt. Lett. 45(20), 5728–5731 (2020). [CrossRef]
38. X. Gu, J. Liu, P. Yuan, X. Tu, D. Zhang, J. Wang, G. Xie, and J. Ma, “Efficient generation of mid-infrared few-cycle pulses by intrapulse difference-frequency generation in YCOB,” Opt. Lett. 47(19), 5244–5247 (2022). [CrossRef]
39. S. Witte and K. S. E. Eikema, “Ultrafast Optical parametric chirped-pulse amplification,” IEEE J. Select. Topics Quantum Electron. 18(1), 296–307 (2012). [CrossRef]
40. J. Liu, J. Ma, J. Wang, P. Yuan, G. Xie, and L. Qian, “Toward terawatt few-cycle pulses via optical parametric chirped-pulse amplification with oxide crystals,” High Power Laser Sci. Eng. 7(4), e61 (2019). [CrossRef]
41. J. Rothhardt, S. Demmler, S. Hädrich, T. Peschel, J. Limpert, and A. Tünnermann, “Thermal effects in high average power optical parametric amplifiers,” Opt. Lett. 38(5), 763–765 (2013). [CrossRef]
42. Z. Yin, J. Ma, J. Wang, P. Yuan, G. Xie, and L. Qian, “Quasi-parametric chirped-pulse amplification simultaneously enables high peak power and high average power,” IEEE Photonics J. 11(4), 1–12 (2019). [CrossRef]
