Investigation Of Rare Earth Doped Fluoride Glass For Visible Laser Generation

Visible lasers are indispensable for applications like medical, consumer electronics, and defense, etc. The visible laser based on rare earth doped fluoride glass host is not only much more efficient, robust and with smaller footprint, but also has wide band tunability and multi-wavelength operation ability. However, the laser efficiency is quite low in all wavelength range except in red wavelength range, and the efficiency is much lower in glass type waveguide(which is beneficial to high power single mode operation) compare to fiber type. The thesis focuses on analyze and improve the efficiency of direct emit visible lasers, software package is developed, spectroscopic and laser properties of several glass are systematically investigated. The main content and innovative research results are as follows:(1) For Pr: ZBLAN glass: the strong gain competition from red emission(635nm) is the limiting factor of laser efficiency in orange range. In F host can suppress the dominate red transition(3P0?3F2) in ZBLAN host, which helps lower the requirement on cavity design and the lasing threshold in orange range. High propagation loss, low launch power and large core diameter are the limiting factor which makes lasing is still not realized in glass type waveguide.(2) For Ho: ZBLAN glass: extraordinary high upper level multi- phonon decay rate, signal re-absorption, mismatch between pump wavelength and energy level spacing are the limiting factor of the up-conversion visible laser. Laser scheme with 449 nm pump source and even lower phonon energy host(such as In F) are proposed and simulated. Threshold power is reduced approximately 70% and 80% respectively when upper level multi-phonon decay rate drops to zero and pump wavelength is switch from 484 nm to 449 nm.(3) For Er: ZBLAN glass: relatively low absorption cross-section and high upper level MP decay rate are the limiting factor of the up-conversion visible laser. Laser scheme with 487 nm pump source and even lower phonon energy host are proposed and simulated. Threshold power is reduced 20-40% when upper level MP rate drops to zero. Although the slope efficiency of green laser is approximately 80%, relative low absorption cross-section makes the threshold power increased sharply when waveguide loss increases. The influence of high doping on the upper level lifetime and laser threshold need to be further investigated.(4) For Tm: ZBLAN glass: low absorption cross-section, coupled with mismatch between pump wavelength and energy level spacing causing the optimal waveguide length is as high as multi meter. Strong ion-ion interaction caused by high doping could lead to dramatically population and lifetime drop of 1G4 upper level. Blue emission from 1D2 upper level(which has higher absorption cross-section when excited by 355 nm UV laser) is proposed. Ion-Ion interaction has little impact on 1D2 upper level even when doping concentration increase to 2mol%.(5) For Tb: ZBLAN glass : even though the upper level life is as high as multi second, extremely low absorption and emission cross-section of Tb: ZBLAN glass causing the optimal waveguide length is as high as multi meter and very sensitive to the waveguide loss when doping concentration is only 0.5mol%. Laser scheme with 355 nm pump source and high doping concentration Tb: ZBLAN fiber are proposed and simulated. Threshold power is reduced approximately 45% and 73% respectively when 355 nm pump source is adopted and the doping concentration is 0.5 mol% and 5 mol%.(6) For Sm: ZBLAN glass: even though absorption cross-section of the glass is ideal and upper level life is as high as 4.35 ms, the emission cross-section is 2 orders of magnitude lower than Pr: ZBLAN. The optimized orange laser efficiency is comparable with Pr: ZBLAN red laser, but lasing threshold and efficiency is very sensitive to the waveguide parameter.