锶原子互组跃迁荧光探测系统的研制

Bias Detector Used for Fluorescence Spectrum of Strontium Intercombination Transition

锶原子单态和三重态间的互组跃迁(5s2)1S0-(5s5p)3P1辐射率远小于一般的电偶极跃迁,共振跃迁荧光信号微弱。介绍了一种应用于探测该互组跃迁荧光谱的直流偏置探测器。该探测器选用极低输入偏置电流运算放大器作为前置放大,具有信噪比高、增益高、偏置可调等优点。此探测器探测增益为106 V/W量级,-3dB带宽为1MHz。实验中利用该探测器对锶原子互组跃迁(5s2)1S0-(5s5p)3P1微弱共振荧光进行探测,获得信噪比很好的共振荧光谱,且无直流偏置,并由此获得高信噪比的鉴频曲线。应用该探测器观测到了饱和荧光谱线以及对应的鉴频曲线,可用于689nm激光锁频,应用于锶光钟系统。

The rate of spontaneous emission of strontium intercombination transition between singlet state and triplet state （5s2）1S0-（5s5p）3P1 is less than the rate of electric dipole transition. Compared with the dipole transition, the fluorescent signal of intercombination transition is very weak. A bias detector is reported which is used to detect the fluorescent signal of this intercombination transition. An ultralow input bias current operational amplifier is applied in this detector to pre-amplify the weak signal, which makes the signal have high signal-to-noise ratio （SNR） and high gain. The detector＇s bias can be adjusted. Its gain is on the order of 106 V/W and 3 dB bandwidth is about 1 MHz. According to our experiment, the weak sympathetic fluorescent signal of （5s2）1S0-（5s5p）3P1 intercombination transition is detected by the detector. Consequently, we obtain the fluorescent signal with high SNR and zero bias. Also we detect the high-SNR error signal of the fluorescent signal. Besides, saturated fluorescence spectrum and its error signal are also acquired by the detector. These signals can satisfy the requirement of 689 nm laser frequency stabilization and then be used for strontium optical clock.