Enhanced optical absorption surface of titanium fabricated by a femtosecond laser assisted with airflow pressure
Xun Li, Ming Li, and Hongjun Liu
We propose an effective way to achieve an enhanced optical absorption surface of titanium alloy 7 (Ti7) fabricated by a femtosecond (fs) laser assisted with airflow pressure. The effect of laser scanning speed and laser power on the surfaces’ morphology and average reflectivity was studied. In order to further reduce the surface’s reflectivity, different airflow pressure was introduced during the fabrication of Ti7 by a fs laser. Furthermore, the average reflectivity of samples fabricated under different laser parameters assisted with airflow was presented. In addition, the high and low temperature tests of all samples were performed to test the stability performance of the hybrid micro/nanostructures in extreme environments. It is demonstrated that the airflow pressure has an important influence on the micro/nanostructures for light trapping, the average reflectivity of which could be as low as 2.31% over a broad band of 250–2300 nm before high and low temperature tests, and the reflection for specific wavelengths can go below 1.5%.
  • Jun. 15, 2021
  • Chinese Optics Letters
  • Vol.19 Issue, 9 091404 (2021)
  • DOI:10.3788/COL202119.091404
Theoretical analysis of periodically poled LiNbO3 nonlinear mirror and its application in a passively mode-locked Nd:YSAG laser
Lina Zhao, Fangxin Cai, Luyang Tong, Ye Yuan, Wenyu Zhang, and Yangjian Cai
  • Jun. 15, 2021
  • Chinese Optics Letters
  • Vol.19 Issue, 9 091403 (2021)
  • DOI:10.3788/COL202119.091403
GSA and ESA dual-wavelength pumped 2.3 μm Tm:YLF laser on the 3H43H5 transition
Fei Wang, Haitao Huang, Haiwei Chen, Yushuo Bao, Zihan Li, and Deyuan Shen
The population trapping effect of the F34 level is an important factor limiting the power scaling of the 2.3 μm thulium (Tm) laser on the H34→H35 transition. In this Letter, we demonstrate a novel scheme of ground state absorption (GSA) (H36→H34) and excited state absorption (ESA) (F34→H34) dual-wavelength pumped 2.3 μm Tm lasers. Introducing an ESA pumping process can accurately excite the Tm3+ ions accumulated in the F34 level to the H34 level, constructing a double populating mechanism for the upper laser level H34. A proof-of-principle experimental demonstration of the GSA (785 nm) and ESA (1470 nm) dual-wavelength pumped 2.3 μm Tm:LiYF4 (Tm:YLF) laser was realized. A maximum continuous-wave output power of 1.84 W at 2308 nm was achieved under 785 and 1470 nm dual-wavelength pumping, increased by 60% compared with the case of 785 nm single-wavelength pumping under the same resonator condition. Our work provides an efficient way to achieve higher output power from 2.3 μm Tm-doped lasers on the H34→H35 transition.
  • Jun. 15, 2021
  • Chinese Optics Letters
  • Vol.19 Issue, 9 091405 (2021)
  • DOI:10.3788/COL202119.091405
Random Bragg-grating-based wavelength-tunable random fiber laser with a full-open cavity
Bing Lü, Wentao Zhang, Wenzhu Huang, and Fang Li
  • Jun. 15, 2021
  • Chinese Optics Letters
  • Vol.19 Issue, 9 091203 (2021)
  • DOI:10.3788/COL202119.091203
Liquid crystal integrated metamaterial for multi-band terahertz linear polarization conversion
Shitong Xu, Fei Fan, Hongzhong Cao, Yinghua Wang, and Shengjiang Chang
  • Jun. 15, 2021
  • Chinese Optics Letters
  • Vol.19 Issue, 9 093701 (2021)
  • DOI:10.3788/COL202119.093701