双波长单纵模掺铒光纤环形激光器设计及实验研究

Design and Experimental Study of Two-Wavelength Single-Longitudinal-Mode Erbium-Doped Fiber Ring Laser

为了实现1550nm正交线偏振双频激光输出,设计了一种复合环形腔双波长单纵模掺铒光纤(EDF)激光器,以保偏光纤Bragg光栅作为波长选择元件,并采用未抽运掺铒光纤饱和吸收体作为激光单纵模选择元件,从而实现正交线偏振1550nm双波长单纵模激光稳定振荡输出。简要介绍了复合环形腔选模及未抽运掺铒光纤饱和吸收体选模的基本原理,理论分析了未抽运掺铒光纤长度对单纵模选择的影响,实验研究了不同选模情况下双波长激光的振荡特性。实验结果表明:腔内含有保偏光纤Bragg光栅和未抽运掺铒光纤饱和吸收体的复合环形腔。掺铒光纤激光器能够稳定输出1550nm正交线偏振双波长单纵模激光,其波长间隔约为0.344nm。这种双波长单纵模光纤激光器可广泛应用于激光传感与测量以及密集波分复用(DWDM)光纤通信等领域。

In order to produce the orthogonally and linearly polarized dual-frequency laser output at 1550 nm, a two- wavelength single-longitudinal-mode erbium-doped fiber （EDF） laser with a structure of compound ring cavity is designed, which employs a polarization-maintaining fiber Bragg grating as the wavelength selector, and uses a saturable absorber of an unpumped EDF as laser single-longitudinal-mode selector. The basic principles of single longitudinal-mode selection of both compound ring cavity and unpumped EDF saturable absorber have been briefly introduced, the effect of the unpumped EDF length on the single-longitudinal-mode selection is theoretically analyzed, and the two-wavelength laser oscillating characteristics are investigated experimentally on different longitudinal-mode selection occasions. The experimental results show that the EDF laser with a compound ring cavity in which both a polarization-maintaining fiber Bragg grating and an unpumped EDF saturable absorber are included can steadily output orthogonally and linearly polarized two-wavelength single-longitudinal-mode laser at 1550 nm, and the wavelength spacing is approximately 0. 344 nm. Such a two-wavelength single-longitudinal-mode fiber laser will find wide applications in the fields of laser sensing and measuring system, dense wavelength division multiplexing （DWDM） optical fiber communications, and so on.