Recently, researchers in Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS), have made new progress in the timing measurement and control of ultrashort laser pulses. The researchers proposed to use double-hump laser spectrum to obtain a near-field interference pattern, which could be used to simultaneously measure the absolute and relative delay of the laser pulses. The time jitter was compensated by a feedback loop. The results were published in Optics Express on November 10, 2020.
Owing to the advantages of high precision, fast response speed, and high signal-to-noise ratio, laser synchronization technology has been used in precision synchronization and control in various fields, such as optical parametric amplification, laser coherent beam combination, and coherent synthesis. The previous technologies can measure the relative delay between laser pulses but are not able to measure the absolute delay accurately.
In this study, the researchers used the double-hump spectrum to obtain the near-field interference pattern of two beams. The absolute delay between laser pulses was accurately measured by the effective recognition of the interference pattern envelope, and the time jitter was controlled by a closed-loop feedback system. A sub-femtosecond synchronization accuracy was achieved. The proposed scheme avoids the influence of absolute delay in the applications of laser synchronization and coherent synthesis and reaches higher synchronization accuracy and peak intensity.
This study has developed a new way of measuring and controlling the absolute delay of laser pulses, that provides a solution for related applications.
The work is supported by the National Key R&D Program of China, Strategic Priority Research Program of the Chinese Academy of Sciences, National Natural Science Foundation of China, Program of Shanghai Academic/Technology Research Leader, etc.
Fig. 1. (a) the near-field interference schematic (the insets show the difference of the interference patterns existing the delay), α is the incident angle between two laser beams, δ is the optical path difference (delay), Δ is the moving distance of interference fringe (the inset); (b) the initial and double-humped spectrum; the simulated results of (c) the initial and (d) double-humped spectrum in different delay (left and right show 2D and 1D interference patterns, respectively). (Image by SIOM)
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Shanghai Institute of Optics and Fine Mechanics, CAS