具有负折射率温度系数的稀土离子掺杂硅酸钪（钇）激光晶体研究

Ytterbium doped ultra-fast laser system with the characterization of broad continuous wavelength,narrow pulse width and high power laser output is widely employed in the areas of microfabrication, spectrascopy and opto-communication etc.. The lowest level of the upper energy-splitting levels is close to the ground state levels and would stimulate thermal block and strong temperature effect which would put laser hosts in serious disavantage during high power laser operation. Sc2SiO5 single crystal possessing the highest thermal conductivity and the exclusive minus colarescence coefficient among silicate crystals is highly expected in the high power laser system as well as the thin disk laser devices. We have realised high efficient CW and fs lsaer output in Yb:Sc2SiO5 crystal. The Yb:(Sc1-xYx)2SiO5 crystal is first put forward as the research subject in this proposal. Through the subsitution of Sc by Y, the segregation coefficient of Yb3+ would be enhanced and the disordered multi-crystallographic sites would be formed which are both guaranty for broader emission spectra and higher gain property, as well as continuous ultra-fast laser output. The proposal will also emphasis on the optimization of LD pumped mode-locked ultra fast laser system together with the modulation of carbon nano-tube saturable absorber (CNTSA) with low cost and high pump threshold to obtain broad continuous and high power ultra fast laser output.

具有宽调谐、窄脉冲和高功率的掺镱超快激光在微加工、光谱学和光通讯等领域有重要应用。但镱离子属三能级系统，其激光下能级接近基态，存在下能级热阻塞、温度效应强的缺点，在高功率激光运转时，对基质材料的热特性要求很高。硅酸盐激光晶体有望用于大功率超快激光器。目前在所有硅酸盐中，硅酸钪(Sc2SiO5)的热导率最高，且是唯一具有负折射率温度系数的晶体。近期本组生长的Yb:Sc2SiO5晶体成功实现高效CW和fs激光输出。基于以上结果，本项目首次提出掺镱硅酸钪（钇）（Yb:(Sc1-xYx)2SiO5）混晶作为研究对象，通过Y取代Sc，提高晶体中Yb分凝系数，形成无序和多格位结构，获得具有更宽发射光谱和高增益特性的可调谐超快激光介质，并重点开展其在半导体激光泵浦下的被动锁模超快激光特性，选择具有低成本、高损伤阈值的碳纳米管饱和吸收体（CNTSA）为调制元件，获得宽调谐、高功率超快激光输出。

具有宽调谐、窄脉冲和高功率的掺镱超快激光在微加工、光谱学和光通讯等领域有重要应用。但镱离子属三能级系统，其激光下能级接近基态，存在下能级热阻塞、温度效应强的缺点，在高功率激光运转时，对基质材料的热特性要求很高。硅酸盐激光晶体有望用于大功率超快激光器。目前在所有硅酸盐中，硅酸钪(Sc2SiO5)的热导率最高，且是唯一具有负折射率温度系数的晶体。本项目采用提拉法生长获得高光学质量掺杂浓度3%、5%掺镱硅酸钪晶体，直径45mm、等径生长部分大于60mm，并生长出系列掺钬、铥、钕硅酸钪（钇）等晶体。LD泵浦Yb:SSO晶体，Yb:SSO薄片激光器中获得平均输出功率280W；泵浦阈值500mW，获得稳定SESAM锁模脉冲71fs、脉冲频率89MHz；LD泵浦Yb:SYSO晶体，实现55fs克尔棱镜锁模输出。