基于波长调制光谱提高光子计数的信噪比  

Improvement of Photon-Counting Signal-to-Noise Ratio Based on Wavelength Modulating Spectroscopy

作　　者：冯晓霞[1] 董双丽[1] 肖连团[1] 贾锁堂[1] 

机构地区：[1]山西大学物理电子工程学院量子光学与光量子器件国家重点实验室,山西太原030006

出　　处：《中北大学学报（自然科学版）》2007年第3期261-266,共6页Journal of North University of China(Natural Science Edition)

基　　金：国家自然科学基金资助项目(10674086);高等学校博士学科点专项科研基金资助项目(20040108002);山西省青年学术带头人基金;新世纪优秀人才支持计划资助项目

摘　　要：光子计数广泛应用于微弱光信号检测中,而光子计数的Poisson统计特性导致光子计数的散粒噪声为N.为了提高光子计数光谱信噪比,采用了波长调制法,即将波长调制的连续激光通过声光调制器的通断控制转化为弱激光脉冲,探测到的光子计数值经过数模转换后,由锁相放大器进行解调.实验中,光子计数荧光光谱来自于Cs原子的D2线6P3/2→6S1/2(F=4)跃迁,荧光光子被探测到的概率为35%.测量结果表明:对二次谐波获得了最大为51 dB的信噪改善比,残余噪声为7.54μV,最小可探测光子数约为3×10-4光子/脉冲.相关研究可应用于单分子及冷分子高分辨光谱的测量.Photon counting has been widely used in weak light even to single photon detection. However, the Shot noise of photon-counting √N for Poisson statistics seriously affects the sensitivity. A method using wavelength modulation spectroscopy technique to improve signal-to-noise ratio of photoncounting is presented. The light from an external cavity diode laser is wavelength modulated and then chopped to a series of laser pulses by using a acoustic-optical modulator, the counts of fluorescence pho- ton are recorded and then converted to an analog signal. The analog signal is added to a lock-in amplifier for harmonic demodulation using lock--in method. The fluorescence spectrum is the 6S1/2（F=4）→6P3/2 transition of Cs D2 line and the detected probability of photon is 35%. The experimental demonstration has achieved a 51 dB signal-to-noise improvement factor in 2f harmonic detection. The minimum de- tectable count here is 3X 10-4 with the residual noise 7. 54 μV. The results show a potential application in fluorescence detection of cold molecules or single molecule.

关 键 词：光子计数 波长调制 散粒噪声 信噪比 

分 类 号：TN29[电子电信—物理电子学]