光纤面板窗多碱光电阴极荧光谱特性研究

Characteristics of Fluorescence Spectrum of Multi-alkali Photocathode of FOP Window

论述了光致荧光的特点以及微光像增强器多碱光电阴极光致荧光的测量原理,测量了光纤面板输入窗多碱光电阴极的荧光谱.测试结果表明,光纤面板窗的多碱阴极的荧光谱不是一条光滑的高斯型曲线,而是在一条高斯型曲线上叠加了一些小的干涉峰的曲线.原因是光纤面板窗所传输的荧光中,有两束特殊的光线.一束光为准直光,另一束光为入射角刚好等于全反射临界角的反射光.这两束光具有固定的相位差或光程.当这两束光的相位差相差λ的整数倍时,它们将干涉并产生干涉加强峰;当这两束光的相位差相差1/2λ的奇数倍时,它们将干涉并产生干涉减弱峰.如果在荧光谱的峰值波长处刚好产生干涉加强峰,那么所测量的峰值荧光强度较其固有的峰值荧光强度要高;反之,如果在荧光谱的峰值波长处刚好出现干涉减弱峰,那么所测量的荧光强度就小于其固有的荧光强度.另外由于受到干涉的影响,荧光曲线半峰宽也不能精确确定,所以在分析光纤面板窗光电阴极的荧光谱时,要考虑到干涉因素的影响.

The characteristics of photoluminescence and the measuring principle of photoluminescence of LLL image intensifier were discussed,and the fluorescence spectrum of multi-alkali photocathode of FOP（optical fiber panel） input window was measured.The test results suggest that the fluorescence spectrum of multi-alkali photocathode of FOP window is not a smooth Gauss curve,but a curve with some small interference peaks being added to a Gauss curve,for there are two special light beams in the fluorescence transmitted by FOP window.One light beam is collimated light and the other is the folded light beam at the very moment when the incidence angle is equivalent to critical angle of total reflection.Both light beams have fixed phase difference or optical path.When the difference between the phase differences of the two light beams lives up to the integral multiple of λ,they will interfere to produce constructive interference peak;when the difference between the phase differences of the two light beams lives up to the odd multiple of 1/2λ,they will interfere to produce destructive interference peak.If constructive interference peak is produced exactly at the peak wavelength of fluorescence spectrum,then the measured peak fluorescence intensity is higher than its inherent peak fluorescence intensity;on the contrary,if destructive interference is produced exactly at the peak wavelength of fluorescence spectrum,then the measured fluorescence intensity is lower than its inherent fluorescence intensity.Furthermore,due to the impact of interference,the half peak width of fluorescent curve can not be accurately determined.Hence,the impact of interference factors should be taken into consideration when analyzing the fluorescence spectrum of photocathode of FOP window.