飞秒时间分辨近场光学系统实现及其应用

Realization of femtosecond-resolved near-field optical system and its application

结合飞秒光脉冲和近场光学显微镜,成功实现了飞秒时间分辨近场光学系统.系统通过高频声光调制和差频锁相探测,极大提高了信噪比并消除了抽运、探测光本底信号,从而在收集模式下测得了飞秒时间分辨的透射光微弱信号变化.同时获得了80nm的空间分辨和小于200fs的时间分辨测量.利用该实验系统,研究了金纳米结构的热电子弛豫动力学过程,观察到不同位置间热电子弛豫动力学的差异.

By combining femtosecond laser with the scanning near-field optical microscope （ SNOM）, we have successfully realized the femtosecond-resolved near-field optical system. Through high frequency acousto-optic modulation and difference frequency lock-in detection, the signal-to-noise ratio was greatly improved and the background signals of the pump and probe light were removed. Therefore, we can measure a femtosecond-resolved weak transmission change in the collection mode SNOM. Spatial resolution of 80 nm and temporal resolution better than 200 fs were achieved simultaneously. Using this system, we studied the relaxation processes of hot electrons in gold nanostrucures and the difference in relaxation dynamics was observed at different sample positions.