Research Progress on Frequency Conversion Technology for Laser Fusion Drivers (Invited)

Song Zhou; Xiangxu Chai; Xiangbing Wang; Fang Wang; Bin Feng; Wei Zhou; Qihua Zhu; Dongxia Hu; Ping Li

doi:10.3788/CJL250957

Chinese Journal of Lasers, Volume. 52, Issue 18, 1803009(2025)

Research Progress on Frequency Conversion Technology for Laser Fusion Drivers (Invited)

Song Zhou^1,2, Xiangxu Chai^1,2, Xiangbing Wang^1,2, Fang Wang¹, Bin Feng¹, Wei Zhou¹, Qihua Zhu^1,2, Dongxia Hu¹, and Ping Li^1,2、*

Author Affiliations

¹Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, Sichuan , China

²State Key Laboratory of Crystal Materials, Jinan 250100, Shandong , China

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Figures & Tables(14)

Fig. 1. Schematic diagram of the Nova laser facility's third-harmonic generation system^[6]

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Fig. 2. Nova laser facility. (a) Schematic diagram of “Type-II/Type-II” third-harmonic generation phase-matching design in the Nova laser facility^[7]; (b) third-harmonic generation conversion efficiency of the Nova laser facility^[6]

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Fig. 3. Beamlet laser facility. (a) Schematic diagram of “Type-I/Type-II” phase-matching design in the Beamlet laser facility^[10]; (b) third-harmonic generation conversion efficiency of the Beamlet laser facility^[9]

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Fig. 4. Comparison between experimental and numerical simulation results of high-efficiency third-harmonic generation on China’s high-power laser facilities (solid line: numerical simulation curve, dashed line: fitted curve according to experimental results)

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Fig. 5. Temperature uniformity test results of large-aperture DKDP crystal. (a) Test device; (b) test results

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Fig. 6. Comparison between experimental and numerical simulation results of third-harmonic generation conversion efficiency

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Fig. 7. Fourth-harmonic generation with focusing beams^[38]. (a) Schematic diagram of fourth-harmonic generation with focusing beams using non-critical phase-matching technique (SHG: second-harmonic generation crystal, FL: focusing lens, FHG: fourth-harmonic generation crystal, DS: debris shield); (b) fourth-harmonic generation experimental results

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Fig. 8. Second-harmonic generation experimental results of three nonlinear crystals^[54]. (a) DKDP; (b) YCOB; (c) LBO

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Fig. 9. Schematic layout of the conversion experiment at Bivoj/DiPOLE^[65]

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Fig. 10. Beam profile of different moments at the third-harmonic frequency under operating conditions of 50 J/10 Hz^[65]. (a) In the beginning of the experiment; (b) after temperature stabilization for 90 min

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Fig. 11. Optimization results. (a) Temperature map of LBO crystal under high-power operation; (b) experimental results of non-critical phase-matching second-harmonic generation

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Table 1. Performance specifications of third-harmonic generation crystals in large-scale laser facilities

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Table 1. Performance specifications of third-harmonic generation crystals in large-scale laser facilities

	NOVA	Beamlet	NIF
D-crystal	KDP（3×3 array）	KDP	KDP
T-crystal	KDP（3×3 array）	KDP	KDP
Size /（cm×cm）	27×27	37×37	42×42
Roughness	<5 nm RMS	<5 nm RMS	<1.5 nm RMS
Roughness PSD2	—	—	<15ν^-1.55， 2.5‒0.12 mm
Scratch/Dig	60/20	60/20	40/15
Transmitted wavefront@633 nm	<0.25 λ	<0.25 λ	5 nm Rq， >33 mm
PSD1	—	—	<15ν^-1.55， 33‒2.5 mm
Transmitted wavefront gradient	<0.25 λ	<0.25 λ	11 nm/cm RMS， >33 mm
Orientation	<30 μrad	<15 μrad	<20 μrad
Wedge /（′）	<2	<1	2±1
Surface flatness /μm	6	6	3.16

Table 2. Evaluation of third-harmonic generation phase-matching accuracy

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Table 2. Evaluation of third-harmonic generation phase-matching accuracy

Control factor	Control accuracy	Equivalent detune angle （Δθ@THG）
Optical axis uniformity	≤0.6×10^-6	~15 μrad
Deuterium content uniformity	±0.05%	~10 μrad
Reflective surface form error	PV≤5λ	~5 μrad
Beam pointing	±5 μrad	~5 μrad
Temperature measurement	±0.1 ℃	~5 μrad
Total	—	~40 μrad

Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation^[54]

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Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation^[54]

	DKDP （98%）	YCOB （XZ）	LBO （XY）
Interaction type	Type-I（e+e-o）
Crystal cut angles /（°）	θ=36.9， φ=0	θ=150.9， φ=0	θ=90.0， φ=13.2
d_eff （pm/V）	0.4	-0.95	0.83
Walk off angle /mrad	2.7	1.8	7.8
Angle acceptance bandwidth /（mrad·cm）	1.35	0.82	4.05
Temperature acceptance bandwidth /（K·cm）	12.7	106	4.2
1 µm absorption coefficient /cm⁻¹	0.0015	0.0015	0.001
Thermal conductivity /（Wm/K）	1.35	2.3	3.5
Damage threshold at 1064 nm /（GW/cm²）	8.4 （1.3 ns pulse）	2.4 （10 ns pulse）	18.9 （10 ns pulse， 10 Hz）
Aperture /（mm×mm）	80×80	30×30	30 diameter
Length of crystal /mm	50	15	15
Coating	Soft gel AR@515 and 1030 nm	E-Beam AR@515 nm and 1030 nm	IAD AR@532 nm and 1064 nm
Calculated efficiency 18 mm diameter beam /%	70	81	60
Calculated efficiency 10 mm diameter beam /%	—	95	86
Biaxial / Uniaxial	Uniaxial	Biaxial	Biaxial

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Song Zhou, Xiangxu Chai, Xiangbing Wang, Fang Wang, Bin Feng, Wei Zhou, Qihua Zhu, Dongxia Hu, Ping Li. Research Progress on Frequency Conversion Technology for Laser Fusion Drivers (Invited)[J]. Chinese Journal of Lasers, 2025, 52(18): 1803009

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Paper Information

Category: Materials

Received: Jun. 16, 2025

Accepted: Jul. 21, 2025

Published Online: Sep. 17, 2025

The Author Email: Ping Li (liping1984@caep.cn)

DOI:10.3788/CJL250957

CSTR:32183.14.CJL250957

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Performance specifications of third-harmonic generation crystals in large-scale laser facilities

Table 1. Performance specifications of third-harmonic generation crystals in large-scale laser facilities

Table 2. Evaluation of third-harmonic generation phase-matching accuracy

Table 2. Evaluation of third-harmonic generation phase-matching accuracy

Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation[54]

Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation[54]

Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation^[54]

Table 3. Key parameters of DKDP, YCOB and LBO crystals for second harmonic generation^[54]