主要介绍了当激光入射到单晶金属Al2O3/Al(111)表面时将发生二次谐波产生(SHG)现象的实验装置和实验方法,利用该装置可以研究SHG和从Al2O3/Al(111)表面反射的SHG在空间各向异性的变化情况,从而可以探测Al2O3/Al(111)表面结构对称性.实验中发现,当脉冲激光功率在2×106 W/cm2～9.6×106 W/cm2范围内变化时,没有检测到SHG信号的各向异性变化;当使用P-极化泵浦激光时,发现Al2O3/Al(111)样品绕法线旋转360度时,P-极化的SHG信号在空间三个方向上呈现最大值相等;当使用脉冲强度为12×106 W/cm2的1064 nm P-极化泵浦激光时,Al2O3/Al(111)表面被损坏,损坏后的表面其SHG信号并不呈现对称的各向异性变化,当使用脉冲强度为11×106W/cm2的1064 nm P-极化泵浦激光时产生表面退火现象,从退火表面所产生的反射532 nm P-极化SHG信号中发现,SHG信号呈现衰减的各向异性成分.
A set of experiments designed to study the anisotropic spatial dependence of second harmonic generation (SHG) from the surface of single crystal metals were presented. The anisotropic dependence of reflected SHG from Al2O3/Al(111) interface was studied. The isotropic dependence of the SHG signal is used to probe the structural symmetry of Al2O3/Al(111) interface. The SHG probe was also used to follow pulsed laser annealing (PLA) of the Al2 O3/Al(111) interface. For peak laser powers per pulse ranging from 2×106 W/cm2 to 9.6×106W/cm2, the anisotropic dependence of the SHG signal was not found to vary from experiment to experiment. Using P-polarized pump laser light, the P-polarized SHG signal exhibits three equally spaced, equal intensity maxima during a single complete rotation of the AlaO3/Al(111) interface about the interface normal. When the incident P-polarized 1064 nm pump laser light possesses an incident peak power of 12×106 W/cm2per pulse, the Al2O3/Al(111) interface is damaged. After this damage is made, the interface does not exhibit a symmetrical anisotropic dependence in the SHG signal. Annealing of the interface is found to occur when the incident P-polarized 1064 nm pump laser light has an incident peak power of 11×106W/cm2 per pulse. The intensity of the P-polarized 532 nm SHG signal generated in reflection from this annealed interface exhibits a reduced anisotropic component in the SHG signal.
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