Phase Characteristics of Laser Beam in Fibers

摘要

The phase changing rates of laser beam in single mode polarization maintaining fiber (PMF), Yb-doped rectangular inner cladding dual-clad fiber (DCF) and Yb-doped large-mode-area dual-clad fiber (LMF) are investigated by means of interference under situations with different exterior disturbance, for situations that all the fibers are used as transmission medium only, as well as amplifying medium with the last two. In this paper, phase fluctuation characteristics of the beam transmitted through the fibers with no amplification are presented. The results show that the phase fluctuation frequencies of the laser beam transmitted through these three kinds of fibers are mainly in the range of 100～200Hz, 100～300Hz and 80～400Hz respectively in normal laboratory environment. The phase fluctuation frequencies of the laser beam transmitted through the DCF, in cases of when the environment temperature is changing, a constant pressure is applied to the fiber and when vibration is applied, are mainly in the range of 100～600Hz, 100Hz～300Hz and 100～500Hz respectively. In the same cases, for the LMF, the phase fluctuation frequencies are mainly in the range of 150～600Hz, 100～400Hz and 100～1000Hz, respectively. It indicates that for realizing phase stabilization, the bandwidth of any potential phase control system has to be in the range of a few kilohertz.