Contents I. Introduction
Low noise and narrow linewidth lasers play key roles in the fields of high technologies and scientific researches, such as microwave photonics, transfer of time and frequency standards, high speed coherent optical communications, high-precision laser spectroscopy and metrology, optical fiber sensors, cold atomic physics, and many fundamental researches [1]–[8]. The intensity noise in low frequency range, especially the 1/ noises, gives notable and serious impacts on performances of optical metrology and sensors, laser spectroscopy and so on. In high speed optical communications and microwave photonics the laser sources are required not only working in a single longitudinal mode with narrow linewidth, but also with low intensity noises in high frequency range, where the frequency of data to be processed is located mostly.
