High Power Laser Science and Engineering, Volume. 12, Issue 1, 010000e9(2024)
Theoretical analysis of frequency modulation-to-amplitude modulation on the final optics and target of the SG II-Up laser facility
Figures & Tables(17)
Fig. 1. Schematic layout of the SG II-Up laser facility and the key unit that causes FM-to-AM conversion. DFB fiber laser, distributed feedback fiber laser; AOM, acoustic-optical modulator; YDFA, ytterbium-doped fiber amplifier; BS, beam splitter; APC, automatic polarization controller; 2-stage-PM, two-stage phase modulator; AFG, arbitrary function generator; AWG, arbitrary waveform generator; EOM, electro-optical modulator; SYNC, synchronization controller; EAMP, electric amplifier; ATD, adjustable time delay; CSF, cavity spatial filter; TSF, transmission spatial filter; AMP, amplifier; FCC, frequency conversion crystal; WFL, wedge focusing lens; BSG, beam sampling grating.
Fig. 3. (a) The 3 GHz sinusoidal phase modulation spectrum; (b) the 3 + 20 GHz sinusoidal phase modulation spectrum.
Fig. 4. AM spectrum of several transfer functions: (a) pure phase transfer function; (b) symmetric exponential amplitude transfer function; (c) asymmetric exponential amplitude transfer function; (d) linear amplitude transfer function.
Fig. 5. Analysis diagram of FM-to-AM influencing factors of the high-power laser facility.
Fig. 6. Schematic diagram of dispersion compensation for the parallel grating pair.
Fig. 7. Temporal modulation (a) before and (b) after GVD compensation for 0.3 nm @ 3 GHz + 20 GHz phase modulation.
Fig. 9. Configuration of the final optics components of the SG II-Up facility.
Fig. 10. When the FM-to-AM is 5% @ 3 GHz, 0.15 nm after the main amplifier, the FM-to-AM on the subsequent optical components and the target surface: (a) last transmission reflector surface; (b) incident surface of the WFL; (c) BSG; (d) target.
Fig. 11. Time-domain modulation (measured by an Agilent DSO93004L with 30 GHz and an EOT ET-3600 with 22 GHz) at different wavelengths for the High Energy Integrated Laser Beam of the SG II-Up facility: (a) wavelength at 1052.5 nm (4.3%); (b) wavelength at 1053 nm (4.9%).
Fig. 12. Phase modulation with 3 GHz + 20 GHz: (a) after the main amplifier (
); (b) incident surface of the WFL; (c) BSG; (d) target.
Fig. 13. (a) Temporal modulation before (blue) and after (red) the WFL; (b) AM spectral transfer function.
Table 1. Spatial filters parameters and FM-to-AM caused by the pinhole.
View tableView in ArticleTable 1. Spatial filters parameters and FM-to-AM caused by the pinhole.
Spatial filtera Input lens focal length (mm) Incident beam aperture (mm) Pinhole aperture ( $\unicode{x3bc} {\mathrm{rad}}$ FM-to-AM modulation TSF-1 22,500 310 ±101.9 0.093% TSF-2 22,500 310 ±203.8 0.043% CSF-1 11,883 310 ±203.8 0.087% CSF-2 11,117 290 ±217.9 0.080% CSF-3 11,883 310 ±203.8 0.087% CSF-4 11,117 290 ±217.9 0.080% Total —— —— —— 0.2%
Table 2. FM-to-AM conversion of laser free transmission to the surface of each transmission mirror and the incident surface of the final optics.
View tableView in ArticleTable 2. FM-to-AM conversion of laser free transmission to the surface of each transmission mirror and the incident surface of the final optics.
Spacing (mm) Modulation After main amplifier 5% WPa 500 4.996% TM1 8970.1 5.020% TM2 2683.8 5.028% TM3 10,216.3 5.056% TM4 5103.4 5.070% TM5 6450.2 5.088% TM6 1608 5.092% CPP 2783.5 5.100% Vacuum window 10 5.100% FCC 60 5.100% WFL 612.5 15.088% BSG 306.9 15.089% Target 2005.6 13.710%
Table 3. Proportion of each frequency modulation component before and after focusing.
View tableView in ArticleTable 3. Proportion of each frequency modulation component before and after focusing.
Spectral component 3 GHz 6 GHz 17 GHz 20 GHz 23 GHz 40 GHz Before focusing 0.68% 0.78% 3.09% 9.14% 3.11% 3.17% After focusing 0.64% 0.60% 0.80% 1.70% 0.23% 0.27% Transmission rate 0.97 0.65 0.22 0.20 0.06 0.075
Table 4. FM-to-AM conversion of laser free transmission to the surface of each transmission mirror and the incident surface of the final optics.
View tableView in ArticleTable 4. FM-to-AM conversion of laser free transmission to the surface of each transmission mirror and the incident surface of the final optics.
Spacing (mm) Modulation After main amplifier ~5% WPa 500 5.000% TM1 8970.1 5.353% TM2 2683.8 5.459% TM3 10,216.3 5.862% TM4 5103.4 6.063% TM5 6450.2 6.317% TM6 1608 6.381% CPP 2783.5 6.490% Vacuum window 10 6.491% FCC 60 6.493% WFL 612.5 18.979% BSG 306.9 18.989% Target 2005.6 4.921%
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Yujia Zhang, Wei Fan, Jiangfeng Wang, Xiaochao Wang, Xinghua Lu, Dajie Huang, Shouying Xu, Yanli Zhang, Mingying Sun, Zhaoyang Jiao, Shenlei Zhou, Xiuqing Jiang. Theoretical analysis of frequency modulation-to-amplitude modulation on the final optics and target of the SG II-Up laser facility[J]. High Power Laser Science and Engineering, 2024, 12(1): 010000e9
Paper Information
Category: Research Articles
Received: Aug. 11, 2023
Accepted: Nov. 10, 2023
Published Online: Feb. 19, 2024
The Author Email: Wei Fan (fanweil@siom.ac.cn)
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