研究了b轴10 at.% Er∶YAP晶体的偏振吸收和输出特性以及多波长激光运转特性。 首次测量了Er∶YAP晶体的偏振吸收光谱, 结果显示晶体对偏振方向平行于a轴和c轴的偏振光在4I11/2能级对应的吸收峰附近的最大吸收系数分别为4.606 3 cm-1 (975.2 nm处)和2.936 6 cm-1(967.6 nm处), 因此选择合适波长的线偏振光作为泵浦光有利于提高晶体对泵浦光的吸收效率, 从而改善激光性能; 在氙灯泵浦的激光实验中, 自由运转条件下实现了2 710, 2 728, 2 795和2 918 nm等4条谱线的激光输出, 并分别研究了各谱线的偏振特性和起振的阈值特性。 通过在谐振腔内加JGS石英片、 云母片、 K9镜片等选择性吸收片分别实现了2 918 nm单波长, 2 710, 2 821, 2 837和2 862 nm等四波长和2 710 nm单波长的激光输出。 测量了自由运转和不同选择性吸收片条件下的激光光谱, 并与不同选择性吸收片的透过谱及之前报道的荧光光谱进行对照分析, 证明通过调节谐振腔能够对Er∶YAP晶体中的起振谱线进行选择。 偏振激光实验结果表明除谱线2 918 nm是偏振方向平行于a轴的线偏振光, 谱线2 728 nm有时是偏振方向平行于c轴的线偏振光, 有时又是偏振椭圆长轴平行于YAP晶体a轴的部分偏振光外, 谱线2 710和2 795, 2 821, 2 837和2 862 nm均为偏振方向平行于c轴的线偏振光; 在LD端面泵浦条件下, 得到2 710, 2 728, 2 750和2 795 nm四条谱线的激光输出, 其中谱线2 750 nm首次在Er∶YAP晶体中实现激光输出, 这四条谱线均为偏振方向平行于晶体c轴的线偏振光; 此外, 首次测量了该晶体在8 K低温下的吸收光谱, 利用Gauss函数对光谱进行分峰拟合, 根据拟合结果对激光上下能级各斯塔克子能级进行了能级指认, 并结合Er∶YAP晶体激光光谱、 荧光光谱对可能的谱线跃迁进行了辨认。 Er∶YAP晶体偏振特性和多波长讥光运转特性的研究以及对后续Er∶YAP晶体调Q等技术的实现和电光调Q晶体的选择具有一定的指导意义。

In this paper, the polarization absorption and output characteristics and the multi-wavelength laser operation characteristics of 10 at.% Er∶YAP crystal are studied. The polarization absorption spectra of Er∶YAP crystal is measured for the first time, the result indicated that the maximum absorption coefficients of crystal to linearly polarized light parallel to axis a and axis c in the absorption peak corresponding to the 4I11/2 energy level are 4.606 3 cm-1 (at 975.2 nm) and 2.936 6 cm-1 (at 967.6 nm), respectively. Therefore, the absorption efficiency of Er∶YAP crystal to pump light can be improved by choosing linearly polarized pump light with properly wavelength, which is conducive to improving the laser performance. In the xenon lamp pumped laser expeiments, four spectral lines of 2 710, 2 728, 2 795 and 2 918 nm are realized laser output under the free operation condition, the polarization and threshold characteristics of each spectral line are studied respectively. The laser output of single wavelength of 2 918 nm, four spectral lines of 2 710, 2 821, 2 837, 2 862 nm and single wavelength of 2 710 nm are achieved by adding JGS quartz plate, mica plate and K9 lens selective absorber respectively in the resonator cavity. The laser spectra are measured under the conditions of free operation and different selective absorbers, As well by contrasting with the transmittance spectra of different selective absorbers and the previously reported fluorescence spectra, it is proved that the oscillation is starting spectrum lines in Er∶YAP crystal could be selected by adjusting the resonator cavity. The experimental results show that the polarization direction of 2 918 nm spectral line is parallel to axis c and the polarization direction of 2728 nm spectral line sometimes parallel to the axis c and sometimes parallel to the axis a, besides, the polarization direction of all other spectral lines like 2 710, 2 795, 2 821, 2 837 and 2 862 nm are parallel to the axis c. The four laser spectral lines of 2 710, 2 728, 2 750 and 2 795 nm are obtained under LD end-pumping condition, in which the spectral line of 2 750 nm is realized laser output in Er∶YAP crystal for the first time. All these four spectral lines are linearly polarized light with polarization direction parallel to the c axis of the crystal. In addition, the absorption spectrum of Er∶YAP crystal is measured in 8 K low temperature, the spectrum was peak fitted by Gauss function, according to the fitting results the stark level of the upper and lower level are identified. And combining the laser spectra and fluorescence spectra, the possible laser spectral line transitions are also recognized. In this paper, the research of the Er∶YAP crystal polarization characteristics and multi-wavelength laser operating characteristics have instructive significance for the realization of Er∶YAP crystal Q-switching technique and the selection of electro-optic Q-switching crystal.