| In the visible light range,whether it is a pulsed laser or a continuous wave laser,there are a wealth of applications,including optoelectronic display,underwater communication,laser processing,bio-photonics,remote detection and scientific research.All-fiber lasers are compact and have the advantages of low heat loss,high beam quality,and high pumping efficiency.The laser realized by the fluoride-doped fiber doped with rare earth ions is more efficient because the phonon energy in the fluoride fiber is lower(580 cm-1)than the ordinary quartz fiber,so it can be effectively reduced the non-radiative transition due to multi-phonon relaxation,therefore it also has the advantage of small transmission loss(～0.1 dB/m).Until now,some fiber lasers doped with rare earth ions have appeared in the reports.Among them,Pr3+ and Ho3+ have abundant lasing wavelengths in the visible range,including green light(521nm/549nm),orange light(604nm/607nm),red light(635nm),and deep red light(715nm).However,self-Q-switched fiber lasers based on the above-mentioned gain fiber have been rarely reported,and most of the reported lasers are not complete bands,output performance is low,and not all-fiber structures.Based on that,this paper first introduces the research progress of Ho3+-doped and Pr3+-doped fiber lasers,and then studies the～550nm green continuous-wave Ho:ZBLAN fiber laser and self-Q-switched laser.Finally,the research on the two-wavelength continuous wave laser based on Pr:ZBLAN is carried out.Below is the three parts into which We will separate the main work:Ⅰ)Basic theoretical analysis and research on Ho3+-doped ZBLAN fiber laser and Pr3+-doped ZBLAN fiber laser,including the energy level structure,spectral characteristics,fluoride fiber characteristics.Meanwhile,the absorption spectrum and emission spectrum of the gain fiber are also introduced.The principle of Q-switching is briefly explained,which lays a foundation for subsequent experimental research.Ⅱ)Manually polishing the Ho’+:ZBLAN fiber with polishing paper.With the coating chamber conditions,using plasma sputtering to coat the end face of the quartz fiber,an input mirror with a high transmission of 450nm blue light(72%@450nm)and a high reflectivity of 549nm green light(0.05%@549 nm)and an output mirror for partial transmission of green laser light(6.5%@549nm)were obtained.A green～550nm Ho3+-doped ZBLAN self-Q-switched fiber laser is realized.The output threshold of the laser is 190mW,Q-switched threshold is 245mW,maximum output power is 44.5mW,slope efficiency is about 27%,and the maximum single pulse energy is 264nJ,the pulse width ranges from 1010ns to 889ns,pulse repetition frequency is 58.61 kHz-70.59kHz,and the signal-to-noise ratio is 41dB.This work demonstrates a single-wavelength～550nm self-Q-switched Ho:ZBLAN fiber lasers for the first time.Ⅲ)A red-green dual-wavelength continuous-wave Pr3+:ZBLAN fiber laser is realized using a fiber end-face coating mirror.The input mirror is highly transparent to the pump source and highly reflected to the 521nm green light(70.5%@444nm,0.06%@521nm).The output mirror is a coating mirror with transparency of 6.4%and 24.8%at 521nm and 635nm respectively.The laser threshold is 130mW,maximum output power is 58mW,and the slope efficiency is 16.1%.The orange dual-wavelength continuous-wave Pr3+-doped ZBLAN fiber laser is also completed.The input mirror transmittance is 70.5%@444nm,11.5%@604nm.The output mirror has an optical transmittance of 34.9%@604nm,37.8%@607nm,a laser threshold of 149mW,a maximum output power of 17mW,and an slope efficiency of 7.2%. |
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