The laser spatial distribution measurement is an important branch of the laser measurement system, which is mainly composed of the near-field distribution of the laser beam and the far-field distribution of the laser beam. With the development of laser science, more and more attention has been paid to the spatial distribution of laser beams. In the history of the development of high-power laser pointer, the spatial distribution of laser beams is the most important field, and its level determines the level and scale of laser devices to a great extent.
In the successful development of the Shenguang II device, the development of the laser beam spatial distribution diagnostic instrument is a crucial sum. Innovatively designed by the academician Lin Zunqi, the “three-darkroom small-hole coupled laser near-field diagnostic instrument” and the “two-step method in laser far-field diagnosis to diagnose six orders of magnitude of laser far-field side-lobe intensity distribution” not only improve The measurement method of the spatial distribution of the beam, and also expanded the new measurement technology, so that the spatial distribution of the laser beam has been more comprehensive and in-depth display.
The laser time measurement is mainly to monitor the pulse laser waveform output by the final stage of the Shenguang II integrated device in real time, the green laser pointer time synchronization measurement that reaches the bullseye at the same time when each laser target is shot, and the laser time measurement during the ultrashort pulse experiment. Laser time waveform refers to the shape of laser intensity that changes with time, and is an important parameter in physical simulation calculations. In high-power laser systems, laser time measurement is mainly divided into ns-level measurement and ultra-short time ps measurement.
In the ns-level laser system, a test system composed of a fast-response photoelectric probe and a fast-response oscilloscope is mainly used. Because the fast-response photoelectric cell has a fast rise (60 ps) and a falling edge (55 ps), it has a basic The triple frequency band has a response, so the measurement system composed of the fast response oscilloscope has become the standard configuration of the high-power laser device. The measurement accuracy of the waveform measurement using this pulse time measurement system is better than 10%.
In ultrashort pulse laser time waveform measurement, picosecond measurement is generally measured with a fringe camera (time resolution is about 2 picoseconds), while femtosecond measurement requires autocorrelation technology. Laser time synchronization (equal optical path) measurement refers to the measurement of the time when multiple beams of red laser pointer reach the target point simultaneously, and is an important guarantee for the power balance of the laser beam target surface. According to physical calculations, if the time difference between the two beams is 25 ps, it will cause a 10% power imbalance. Power balance is extremely important to achieve uniform compression of the target by multiple laser beams. The synchronization accuracy requirement of the US LLNL laboratory is 10 ps.