飞秒级瞬态过程的数字全息极高速分幅成像技术研究

The essence of the high-speed imaging technology is time expanding. It can record the transient process which beyond the time resolution of human eye, and playback slowly with normal speed. It is a powerful tool for study of transient events and widely used in chemistry, physics, biology and other fields. In recent years, with the development of scientific research, the studies of high-speed imaging have going into femtosecond order. In this scale, femtosecond digital holographic imaging technology with extremely high speed framing rate is of particularly important. The project is based on the applicant's post research of holographic imaging with ultra-short laser pulse. Its goal is to develop an extremely high-speed digital holographic framing imaging system. For framing and high-speed formation of the system, two methods were proposed regarding to two typical kinds of femtosecond order process. One is controllable wavefront encoding of single pulse and the other is adjustable framing time of multi-pulse to generate sequence pulse train. For synchronization control, we use special designed electronic control circuit to realize precise synchronization control with nanosecond. 35fs imaging time resolution and 10^13 fps imaging frequency could be achieved of the presented system in this project which contains two framing scheme. The technology provides a novel and effective method for the imaging of events in atomic time.

高速成像技术的实质是时间放大，它将远超出人眼时间分辨能力的瞬态过程快速记录并通过慢回放放大时间尺度，是目前研究瞬态事件的有力工具，被广泛应用于化学、物理、生物等领域。近年来随着科学研究的发展，对于高速成像的需要已经深入到飞秒量级，在这个尺度上，飞秒数字全息极高速分幅成像技术就显得尤为重要。 本项目立足于申请人前期在超短激光脉冲全息成像原理和方法方面的积累，旨在发展适用于飞秒级瞬态过程研究的数字全息极高速分幅成像技术。在分幅与极高速形成这个关键模块中，针对两类飞秒级瞬态过程，项目分别提出单脉冲可控波前编码方法和多脉冲分幅时间可调序列成像脉冲产生方法；在同步控制模块中，采用自制电子控制电路实现多元件的纳秒级精确同步控制。本项目提出的包含两种分幅方式的系统，预计都可实现成像时间分辨率35fs，成像频率10^13 fps的指标，该技术为原子时间的成像提供一种新型有效的手段。

观测原子时间过程的光信息，准确揭示原子运动过程中所发生的物理、化学和生物的变化规律，将有助于推动人类科学的进步。这也是目前科学家们研究的热点之一。针对目前对原子时间过程观测的难点，本项目发展适用于飞秒级瞬态过程研究的数字全息极高速分幅成像技术。根据不同成像需求，设计两种分幅成像方案，分别为单脉冲可控波前编码和多脉冲分幅时间可调序列成像技术。项目课题组对这两种方案进行数学建模，计算优化各系统参数，模拟计算获取最优结构设计。通过这两种技术的实施，实现成像时间分辨率35fs，成像频率10^13fps 的指标。在研究过程中，根据实验条件，更进一步优化光路，提出采用频域全息来记录超快过程，通过初步实验验证该方法的可行性。