High Power Laser Science and Engineering, Volume. 12, Issue 6, 06000e71(2024)
Performance enhancement in the long-wavelength low-gain region of Ti:sapphire lasers by an efficient stimulated Raman scattering process
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Fig. 1. Schematic of the high-performance high-gain-band Ti:sapphire intracavity Raman laser operating in the 930–1000 nm low-gain region of the Ti:sapphire laser.
Fig. 2. (a) Pulse establishment of the Ti:sapphire Raman laser. (b) Simulated Stokes power transfer for various OC reflectivities.
Fig. 3. Maximum output powers of the narrow-linewidth Ti:sapphire and Raman lasers with various OC reflectivities.
Fig. 4. Power transfer and conversion efficiency at 800 nm. Inset: measured fine spectrum, pulse duration and beam quality at 10.55 W.
Fig. 5. Maximum output power at 700–970 nm for various OC transmittances.
Fig. 6. Power transfer of first- and second-order Stokes waves for various OC transmittances.
Fig. 7. Measured fine spectrum of Stokes waves with OC transmittance of 30%.
Fig. 8. (a) Power transfer and conversion efficiency of first-order Stokes wave with OC transmittance of 60%. (b) Measured fine spectrum of Stokes waves of the
Fig. 9. (a) Power transfer and (b) conversion efficiency of the Stokes outputs with various OC transmittances.
Fig. 10. Mode-locked modulations of the (a) first-order Stokes pulses (3.24 W), (b) second-order Stokes pulses (0.39 W) and (c) first-order Stokes pulses (near threshold).
Fig. 11. Beam quality at the maximum output powers of 960 and 1036.5 nm with an OC transmittance of 40%.
Fig. 12. Stability of the first-order Stokes output power at 960 nm within 1 h with an OC transmittance of 40%. Inset: power stability within 10 min.
Fig. 13. (a) Maximum output powers and fine spectra of the first-order Stokes wave at 900–1000 nm. (b) Fine spectrum of the second-order Stokes wave at 1083.7 nm.
Table 1. Coatings of mirrors.
View tableView in ArticleTable 1. Coatings of mirrors.
Mirrors Coatings M1, M2, M3, M4 45° 532 nm high reflectivity (HR) M5 45° 532 nm HR, 45° 700–1000 nm high transmittance (HT) M6, M7 700–1000 nm HR M7* (OC) 700–1000 nm T = 40% M8 45° 790–810 nm HT, 45° 840–870 nm HR M8* 45° 840–890 nm HT, 45° 900–960 nm HR M8** 45° 890–930 nm HT, 45° 960–1000 nm HR M9 (OC) 850–1000 nm @ T = 30%/40%/50%/60% M10 M8*/ M8**/900–970 nm HR, 1000–1100 nm HT/950–1000 nm HT, 1050–1100 nm HR
Table 2. Related parameters used in calculations[23,24].
View tableView in ArticleTable 2. Related parameters used in calculations[23,24].
Symbol Parameter Value h Planck constant 6.626 × 10–34 J s c Light velocity in the vacuum 3 × 108 m/s lL Length of gain medium (Ti:sapphire crystal) 13 mm lS Length of Raman crystal (KGW crystal) 30 mm nT Refractive index of gain medium 1.7602 @ 800 nm nK Refractive index of Raman crystal 1.99 @ 852.9 nm σ Stimulated emission cross-section of gain 3 × 10–23 m2 @ medium 800 nm τ Fluorescent lifetime in upper level of gain medium 3.2 μs ωp Pump beam radius in gain medium 0.25 mm ωL Average radius of Ti:sapphire laser in cavity 0.25 mm ωS Average radius of Stokes wave in cavity 0.16 mm LL Length of laser cavity 253 mm LS Length of Raman cavity 110 mm η Pump absorption ratio of gain medium 88% fp Pulse repetition rate of the pump wave 10 kHz T0 Pulse duration of the pump wave 69 ns P0 Maximum input pump power 42 W RL Output coupler reflectivity at laser wavelength 0.99 RS Output coupler reflectivity at Stokes wavelength αS Roundtrip dissipative optical loss of Stokes wave 0.04 αL Roundtrip dissipative optical loss of laser 0.06 g0 Line-centre monochromatic Raman gain coefficient 4.4 cm/GW geff Effective Raman gain coefficient 0.4g0
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Yuntao Bai, Xin Ding, Guoxin Jiang, Peng Lei, Ying Xie, Jiangeng Du, Yang Sun, Liang Wu, Guizhong Zhang, Jianquan Yao. Performance enhancement in the long-wavelength low-gain region of Ti:sapphire lasers by an efficient stimulated Raman scattering process[J]. High Power Laser Science and Engineering, 2024, 12(6): 06000e71
Paper Information
Category: Research Articles
Received: Feb. 26, 2024
Accepted: Jun. 17, 2024
Published Online: Dec. 3, 2024
The Author Email: Xin Ding (dingxin@tju.edu.cn)
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