Li Angzhen, Ward Jonathan M, Tian Ke, Yu Jibo, She Shengfei, Hou Chaoqi, Guo Haitao, Nic Chormaic Síle, Wang Pengfei
Opt Express. 2024 Jan 29;32(3):3912-3921. doi: 10.1364/OE.509662.
In this work, the concentration of rare-earth ions in doped silica whispering gallery lasers (WGLs) is controlled by evaporation. The fabrication of WGLs is used to experimentally evaluate the evaporation rate (mol/μm) and ratio (mol/mol) of erbium and silica lost from a doped fiber during heating. Fixed lengths of doped silica fiber are spliced to different lengths of undoped fiber and then evaporated by feeding into the focus of a CO laser. During evaporation, erbium ions are precipitated in the doped silica fiber to control the erbium concentration in the remaining SiO, which is melted into a microsphere. By increasing the length of the undoped section, a critical point is reached where effectively no ions remain in the glass microsphere. The critical point is found using the spectra of the whispering gallery modes in microspheres with equal sizes. From the critical point, it is estimated that, for a given CO laser power, 6.36 × 10 mol of Er is lost during the evaporation process for every cubic micron of silica fiber. This is equivalent to 1.74 × 10 mol of Er lost per mol of SiO evaporated. This result facilitates the control of the doping concentration in WGLs and provides insight into the kinetics of laser-induced evaporation of doped silica.
在这项工作中，通过蒸发来控制掺杂二氧化硅回音壁激光器（WGLs）中稀土离子的浓度。利用WGLs的制备来实验评估加热过程中掺杂光纤中铒和二氧化硅的蒸发速率（mol/μm）以及损失比例（mol/mol）。将固定长度的掺杂二氧化硅光纤与不同长度的未掺杂光纤进行熔接，然后通过送入CO激光器的焦点进行蒸发。在蒸发过程中，铒离子在掺杂二氧化硅光纤中沉淀，以控制剩余SiO₂中的铒浓度，剩余的SiO₂被熔化成微球。通过增加未掺杂部分的长度，可达到一个临界点，此时玻璃微球中实际上没有离子残留。利用尺寸相同的微球中回音壁模式的光谱来找到临界点。根据临界点估计，对于给定的CO激光功率，每立方微米的二氧化硅光纤在蒸发过程中损失6.36×10⁻⁶ mol的铒。这相当于每蒸发1 mol的SiO₂损失1.74×10⁻⁶ mol的铒。该结果有助于控制WGLs中的掺杂浓度，并为激光诱导掺杂二氧化硅蒸发的动力学提供了深入了解。
