提出并论证了一种新型双频激光器研究方案,即在激光二极管(LD)抽运Nd:YAG激光器的谐振腔内,插入一只集纵模选择与纵模分裂于一体的多功能元件――晶体石英F-P标准具。因腔内存在双折射效应,每一激光纵模分裂为两个相互正交的线偏振模,即o模和e模；同样,Nd:YAG激光增益带宽范围内标准具的唯一透射极大峰也一分为二,即分裂为o峰和e峰。使一个o模位于o峰的峰顶处,并使一个e模位于e峰的峰顶处,即可实现o模和e模的同时运转。将厚度为0.645mm,切割角(晶体光轴与晶体表面法线间的夹角)为10°的晶体石英F-P标准具,置于腔长为40mm的Nd:YAG激光谐振腔内,获得了双纵模同时振荡输出,其频差约为2GHz。

A novel scheme ofdual-frequency Nd:YAGlaser is proposed and demonstrated. The resonant cavity of the laser contains a piece ofversatile element: crystal-quartz-made birefringent Fabry-Perot etalon, serving as both aselector and a splitter of laser axial-modes. Because of the intra-cavity birefringence,each longitudinal mode is split into two linearly and orthogonally polarized components,that is, ordinary mode (o-mode) and extra-ordinary mode (e-mode). Meanwhile due to thesame reason, the unique transmission maximum of the etalon within the overall lasingbandwidth of the Nd:YAGlaser is also split into two transmission maxima, namely, ordinary light transmissionmaximum (o-peak) and extra-ordinary light transmission maximum (e-peak). Simultaneousoperation of the two axial modes can be obtained, by making an o-mode coincide with thecentral position of the o-peak, and an e-mode with that of the e-peak. A piece ofbirefringent Fabry-Perot etalon, with a geometrical thickness of 645 micrometers and acut-angle of ten degrees between the quartz crystalline axis and the normal of itssurfaces, has been designed and fabricated. A frequency-difference of approximately twogigahertz has been obtained experimentally, when the above birefringent etalon beingplaced in a 40-millimeter-long cavity of the LD pumped Nd:YAG laser.