Cylindrical Vector Beam Fiber Laser with a Symmetric Two-Mode Fiber CouplerPhotonics Research
- Yang Xu, Su Chen, Zuxing Zhang, Bing Sun, hongdan wan, and Zhiqiang Wang
- received 07/08/2019; accepted 10/05/2019; posted 10/11/2019; Doc. ID 371435
- Abstract: We demonstrate a passively mode-locked all-fiber laser generating cylindrical vector beams (CVBs) just using a symmetric two-mode fiber optical coupler (TMF-OC) for both high-order mode excitation and splitting. Theoretical analyses show that for a symmetric TMF-OC with appropriate taper diameter, second-order mode can be excited and coupled into output tap with high purity, due to the effective index difference of different modes. Based on the fabricated TMF-OC, passively mode-locked fiber laser delivers pulsed CVBs at center wavelength of 1564.4 nm with 3-dB linewidth of 11.2 nm, pulse duration of 2.552 ps and repetition rate of 3.96 MHz. The purity of both radially and azimuthally polarized beams is estimated to be over 96%. Due to simple fabrication method of the TMF-OC and high purity of the generated CVBs, this mode-locked CVB fiber laser with all-fiber configuration has potential applications in optical trapping, optical communications, material processing, etc.