Low-NoiseCompoundRingCavityFiberLaserwithStable Single-Longitudinal-ModeOperation

Low-noisenarrow-linewidthsingle-longitudinal-mode SLM lasershaveseveralimportantapplications inmanyfields suchasgravitationalwavedetection atomicandmolecularphysics timeandfrequencytransfer and precisionmeasurement Currently SLM fiberlasersaredividedintothree maintypes distributedfeedback distributedBraggreflection DBR andringcavitylaser Amongthem theringcavitylaser whichemploysalong cavitydesign facilitatesincreaseincavitygaintoimproveoutputpowerusingrelativelyhigh-gainfibers Aring cavitylasercanalsobeusedinotherapplicationssuchasfrequencytuningandfeedbackcontrolbysimplyinserting opticalcomponentsintoacavity Moreover theQ-valueofafiber-laserresonatorcanbeincreasedbyemployinga longringcavity Thislongcavityhelpsinobtaininganarrowfree-runninglaserlinewidthandreducestherelaxation oscillationfrequencyofthelaser Thisisusefulinsuppressingarelaxationoscillationpeakthroughphotoelectric feedbackcontrol However alongringcavityiseasilyaffectedbecauseofexternal-environmentnoisedisturbances whichleadstoSLMinstability e g modehopping Thusfar theachievedcontinuousoperationtimeofafreerunningcompoundringcavityfiberlaser without modehoppingisonlyseveralhours Therefore althoughin principal afiber-lasersourceexhibitsexcellentperformance itcannotmeetpracticalapplicationrequirements In thisstudy alow-noisenarrow-linewidth-ringerbium-dopedfiberlaseroperatinginaSLM and maintainingits polarizationisreportednbsp;