【摘要】 以SrTiO3晶体作为光克尔介质,建立了一套基于光克尔门技术的超快时间分辨测量系统。由于SrTiO3晶体在强光作用下产生光克尔效应时,同时会产生宽谱带的双光子激发荧光,因此我们一方面通过采用锁相放大探测技术从同频率的荧光背景中提取信号光,另一方面通过设计自动数据采集系统提高测量效率。为避免背景荧光以及泵浦光散射等噪声对光电倍增管的曝光而造成的探测器对信号光的非线性响应,我们通过增加SrTiO3晶体与探测器之间的距离以及采用封闭信号光路来减少因此而造成的测量误差。以小于150fs波长为800nm的激光脉冲作为泵浦光,其倍频光作为信号光,采用该系统实验得到了约200fs的时间分辨率。更多还原

【Abstract】 Using the SrTiO3 crystal as the optical Kerr medium,we constructe an ultrafast time-resolved measuring system based on the optical Kerr-gate technique. Under the intense light, the SrTiO3 crystal not only exhibits the optical Kerr effect, but also emits a wide spectrum of two-photon excited fluorescence. Consequently, we extract the signals from the background fluorescence with the same frequency using the lock-in amplification technique. As well, a specialized automatic data acquisition system is designed to improve the measurement efficiency. To avoid the nonlinear response of the detector resulting from the saturated exposure by the background fluorescence and the scattered pump light, we cover the optical path of the signal and increase the distance between the SrTiO3 crystal and the detector. Accordingly we experimentally obtain a resolution of around 200 fs using the laser pulses with duration of less than 150 fs and wavelength of 800 nm as the pump and its double frequency as the signal.更多还原