激光自倍频晶体研究和应用进展

激光自倍频晶体是一类同时具有激光和非线性效应的复合功能晶体。以激光自倍频晶体制作的全固态激光器具有体积小,调整方便,稳定性高等优点。自1970年代以来,以LiNbO3,YAl3(BO3)4倍频晶体为基质的激光自倍频晶体实现了自倍频激光运转。近年来,以RECa4O(BO3)3(RECOB)为基质的激光自倍频晶体受到重视和广泛研究。本文从对激光晶体、非线性光学晶体及激光自倍频晶体的基本要求出发,在综述激光自倍频晶体研究历史的基础上,讨论了激光自倍频晶体中的基波和倍频光,探讨了NYAB和Nd:GdCOB一类晶体中晶体长度,Nd3+浓度和效率之间的关系。理论估算表明,当浓度适当,晶体长度10mm时,这两类晶体的光–光转换效率可达30%以上。本文总结了NYAB系列晶体的研究历程及RECOB系列激光自倍频研究的思路及取得的成果。在最近10年中,利用山东大学生长的Yb:YAB晶体,获得1.1 W自倍频绿光,光光转换效率为10%;在RECOB体系中,比较了各种晶体的特点,选定Nd:GdCOB为主要研究对象,经过晶体掺钕浓度和长度关系,位相匹配方向、膜系及热工程等多方面研究,获得了1.36 W的545 nm绿光输出,光–光转换效率为17.1%;输出功率为1.03 W时,半小时功率波动不超过1%。这是目前为止,Nd3+离子激光自倍频晶体的最好结果。文章最后介绍了激光自倍频晶体的可能应用。通过理论和实验分析,认为到目前为止Nd:GdCOB是以Nd3+为激活离子最后的激光自倍频晶体,而在Yb3+为激活离子时,Yb:YAB晶体最佳。

Progress on the Research and Potential Applications of Self-frequency doubling Crystals

Self-frequency-doubling(SFD) crystal is a kind of combined functional crystals,which posses both laser and nonlinear optical(NLO) functions in one crystal.All solid state lasers made of SFD crystals are compact,stable,high efficiency and with small volume.Since 1970’s,SFD laser performances haves been conducted based on SFD crystals developed on LiNbO3,YAl3(BO3)4(YAB) matrix crystals.Recently,RECa4O(BO3)3(RE=Y,Gd or Nd;abbreviated as RECOB) crystals have been attracted many attentions and widely investigated.The basic requirements from practice for laser,NLO and SFD crystals were listed.After the summary of previous research on SFD crystal,the fundamental and SHG waves in SFD have been analyzed and the relationships among the Nd3+ concentration,crystal length and the SFD efficiency have been discussed.The calculations showed that under reasonable Nd3+ content,the optical-optical efficiency can reach 30% when the crystal wave path is ca.10 mm in NYAB or Nd:GdCOB crystals.Motivations and ideas for NYAB and RECOB together with the results obtained were reviewed in the paper.During last 10 years,1.1 W SFD green laser has been emitted from Yb:YAB(O–O efficiency 10%),which is the highest SFD output from Yb3+ doped crystal up to now.And the Nd:GdCOB crystal has been considered the optimal SFD crystal in RECOB series.Based on the investigations on Nd concentration,crystal length,optical SFD phase match orientation and thermal engineering,the 1.35 W 545 nm SFD green laser has been achieved with the optical-optical efficiency 17.1%.During the SFD output was 1.03 W,the fluctuation is less than 1% in half an hour.This is the highest SFD output in Nd3+ doped SFD crystals.The potential applications of SFD crystals have been proposed.By the theoretical and exper-iment results,it is concluded that Nd:GdCOB maybe the best SFD in Nd3+ doped crystals and Yb:YAB the best in Yb3+ doped crystals.