In this paper, firstly, the principle, advantages and disadvantages of measurement of laser linewidth by delayed self-heterodyne method is introduced,and the essence of the method is analyzed theoretically. The core components of the measurement system are introduced in detail.Secondly, the self-developed scheme of semiconductor laser with external dual- cavity self-injection structure of the adjustable time-delay fiber is proposed. The linewidth results of lasers with different lengths of time-delay fiber are tested for the single-mode optical fiber system. The power variation of different structures is analyzed. Finally, A narrow-linewidth semiconductor laser with a mean power of 4 mW, a mean linewidth of 1.96 kHz and the side mode suppression ratio is more than 35 dBm is obtained.
|