35 W continuous-wave Ho:YAG single-crystal fiber laser Download: 605次
1 Introduction
High-power solid-state lasers in the
The laser performance in the CW regime is investigated in the present work by utilizing a high-brightness Tm-fiber laser at 1908 nm for the resonant pumping of a Ho:YAG SCF grown by the micro-pulling-down (
2 Experimental details
YAG (
Figure
Fig. 1. (a) Photograph of the end facet of the Ho:YAG SCF. (b) Schematic of the Ho:YAG SCF laser: L1–L3, lenses with , 100 and 150 mm, respectively; M1, M2, bending mirrors; M3, dichroic mirror; PM, pump mirror; OC, output coupler.
3 Results and discussion
High-power CW operation of the Ho:YAG SCF laser was studied at a physical cavity length of 45 mm using different OCs. The low signal single-pass absorption efficiency of the SCF under nonlasing conditions amounted to 94.7% at 1.9 W of incident pump power. Further increasing the pump power to 71.3 W, the absorption efficiency dropped to 82.5% due to the bleaching effect. Under lasing conditions with
Fig. 2. (a) Laser performance of the Ho:YAG SCF laser with different OCs and (b) the corresponding optical spectra. The gray curves are the calculated gain spectra of Ho:YAG[17] with different population inversion parameters .
To evaluate the propagation loss of the SCF, Caird analysis that was modified for the case of high
Fig. 3. Caird plot for the high-power Ho:YAG SCF laser: inverse slope efficiency with respect to the inverse output-coupling loss, i.e., .
Fig. 4. Beam intensity profiles recorded at different output powers with ; is the calculated beam ellipticity from each image.
Far-field beam intensity profiles of the Ho:YAG SCF laser with
The beam propagation factors (
4 Conclusion
In conclusion, we have experimentally demonstrated a high-power Ho:YAG SCF laser inband pumped by a Tm-fiber laser at 1908 nm. With a modified Caird analysis, the propagation loss coefficient of this Ho:YAG SCF was estimated to be
Fig. 5. (a) The measured -factor of the Ho:YAG SCF laser () at different absorbed pump powers and (b) a typical measurement at 7 W output laser power.
The present work is a demonstration of the high quality of the fabricated Ho:YAG SCF. Amplification of ultrashort pulses (including picosecond and femtosecond) near 2
20 Funding
Foundation of Deutscher Akademischer Austauschdienst (DAAD) – Research Stays for University Academics and Scientists (57381327); Natural Science Foundation of Jiangsu Province, China (SBK2019030177); China Scholarship Council (201704910363); Foundation of the Government of the Russian Federation (074-U01).
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Yongguang Zhao, Li Wang, Weidong Chen, Jianlei Wang, Qingsong Song, Xiaodong Xu, Ying Liu, Deyuan Shen, Jun Xu, Xavier Mateos, Pavel Loiko, Zhengping Wang, Xinguang Xu, Uwe Griebner, Valentin Petrov. 35 W continuous-wave Ho:YAG single-crystal fiber laser[J]. High Power Laser Science and Engineering, 2020, 8(2): 02000e25.