Single Frequency Microfiber Laser

With the rapid development of photonics technology, miniaturization, integration, lowcost and high reliability optical devices has become an important development direction.Micro-optical devices related with LOC (Lab-On-a-Chip) have attracted intense attentionsince the concept and model of photon computer have been proposed. As a paramountelement of the integrated optics, micro-laser sources with mirco-resonator in differentconfigurations such as microdisks, micropillars and microspheres have experienced primaryresearch. Due to its simple fabrication, compact structure and low loss, microfiber has beenone of best candidates for the gain medium of micro-laser. With a wide application in areassuch as coherent telecommunication, high resolution sensing, coherent beam combining andLIDAR (light detection and ranging), single frequency laser has been a subject of intenseinvestigation. However, for the intrinsic constriction of low rare earth dopant concentration insilicon glass which limits the net gain per unit length, micro-laser has progressed slowly forthe past few years. The breakthrough of high net gain special active fiber has exploded thebottleneck. Based on the home-made Er3+-Yb3+co-doped phosphate glass fiber with a netgain of up to5.2dB/cm, this dissertation focused on the study of micro-lasers, especially forthe single-frequency narrow-linewidth micro-laser and tunable two-wavelength micro-laser.In this paper, we set up microfiber drawing platform combined the characteristics of thephosphate glass fiber and prepared the microfiber with uniform structure, smooth surface.Based on this, a double-knot resonator with diameters of206and351μm respectively isdesigned which facilitates the single mode selection of laser. Single frequency laser emissionwith2kHz linewidth at1.53μm was obtained from the microfiber resonator, the maximumoutput power is0.95μW.Based on the double-knot resonator mentioned above, we creatively use the phosphateglass fiber to investigate the wavelength tunable ability of the double-knot microfiber laserwith an ultrahigh factor. By carefully adjusting the joining point and length between thetaper-drawn fiber and the double-knot resonator, we proposed a theoretical assumption thatwavelength tunable laser could be achieved by tuning the length of the coupling region andverify it through experiment. By changing the coupling length, the coupling point and theknot diameter, a2kHz single frequency laser with a wavelength tunable range of more than18nm is realized in communication band (C-band). Without using the fiber Bragg grating(FBG), Fabry-Perot etalon filter, fiber ring scheme filter or saturable absorbers, thismicrofiber laser provides a simple method to realize the tunable single frequency operation. On this basis, a compact and tunable dual-wavelength narrow linewidth microfiber laser isachieved. Each wavelength laser spectrum delivers a2kHz linewidth and an opticalside-mode suppression ratio of over31dB. The laser wavelength and frequency separationbetween the two wavelength lasers can be tuned freely by changing the coupling lengthbetween the taper-drawn fiber and the double-knot resonator. Hopefully it will provide a kindof new train of thought for future integrated photonic circuits as a multiple laser source.