Experimental Research On Stable Single-longitudinal-mode Erbium-doped Fiber Laser With Narrow Linewidth

The fiber laser as a representative of modern laser technology has becomethe research focus recently, and possesses a broad market prospect.Single-longitudinal-mode fiber laser is an important branch in the field of fiberlaser. It has been widely used in applications, such as optical fiber sensorsystem, long-range radar, and long-range communication system etc., and playsa meaningful role for the advantages of narrow linewidth, long coherencelength, ease of high-power output and integration. Especially in optical fibersensor, the coherence length of the source is a considerably important factor tothe measurement resolution, and the stability of the source affects the accuracyof the measurement as well. Therefore, a source with long coherence length, i.e.,stable Single-longitudinal-mode laser source with extremely narrow linewith, isparticularly important. Besides, the linewith of laser source affects directly theoverall performance of remote monitoring, remote sensing systems of manyfields of national defense military applications etc., which have highrequirements for the laser source. The performance of classical semiconductorlasers cannot fulfill the demands for laser source in the aforementioned application fields. As a result, the fiber laser with good performance hasgradually become the research focus. At present, the studies of fiber laser focuson narrowing linewith, improving output power as well as tunable wavelengthmultiplexing output etc.This paper aims at the fiber laser, of which the main works are as follows:1. A brief introduction of the principles and characteristics of the fiber laseris presented, which involves types, advantages of the fiber laser as well as asummary of the application fields.2. Detailed analyses in the principles for the fiber laser are carried out. Theexperimental research and analyses are implemented for the typical fiber laserwith ring cavity and the way to improve its performance is proposed.3. A structure based on an improved Mach-Zehnder interferometer (MZI),which consists of two parallel optical fiber ring resonators embedded fiberBragg grating, has been proposed to realize stable, single frequency and narrowline-width laser output by using Vernier Effect and a combination of saturableabsorber. The characteristic of linewith, threshold, stability and single frequencyhave been studied experimentally in details. The results indicate that the outputof the fiber laser can present a good performance with the linewidth of1.09kHzat1549.57nm, low threshold of10.7mW and high stability.4. A scheme of realizing stable dual-wavelength fiber laser based onparallel sub-ring cavity has been proposed. The dual-wavelength fiber laser withcenter wavelength of1558.67nm and1558.77nm respectively has been experimentally demonstrated. We have studied its performance and detected thespectrum of the output laser, the results of which indicate that the fiber laseroperates with single-longitudinal-mode and shows good time stability.At last, we make a summary and outlook of the research work in thisarticle.