Instantaneous two-dimensional photoacoustic wave measuring method based on femtosecond single-pulse interference

Abstract

The invention belongs to the field of optical measurement, and discloses an instantaneous two-dimensional photoacoustic wave measuring method based on femtosecond single-pulse interference. The methodcomprises the following steps: 1) an ultra-fast imaging system is constructed, and the synchronization of a mode-locked femtosecond laser, an acousto-optic pulse selector, a pumping pulse, a detection pulse and a camera frame rate is realized; 2) power amplification is carried out after a femtosecond pulse is subjected to frequency reduction: the frequency reduction is carried out on the mode-locked femtosecond laser with high repetition frequency, and the power amplification is carried out on the femtosecond pulse subjected to the frequency reduction; 3) a photoacoustic wave induction generating module is used for forming photoacoustic waves and filtering out light background noises; 4) a Mach-Zehnder interference method is adopted to realize reference light and measurement light interference, the reference light is subjected to high-frequency modulation, and a signal-to-noise ratio of interference fringes is increased; and 5) a single-pulse interference image is acquired within single camera exposure time, and instantaneous two-dimensional photoacoustic wave measurement is completed by utilizing a Fourier transform phase reconstruction algorithm. By utilizing time synchronization of camera exposure and ultrashort pulses, ultrafast imaging of subpicosecond time resolution is obtained through experiments.

Description

technical field [0001] The invention belongs to the field of optical measurement, in particular to an instantaneous two-dimensional photoacoustic wave measurement method based on femtosecond single pulse interference. Background technique [0002] Ultrafast laser-induced photoacoustic imaging can be used for the study of nonlinear absorption and refraction properties of materials, spectral imaging of biological objects and non-invasive detection of subsurface microelectronic damage. The instantaneous observation of photoacoustic waves with a large field of view is a very challenging task. So far, due to the lack of high-speed two-dimensional sensors, the characterization of photoacoustic waves generally uses one-dimensional piezoelectric or laser vibration with limited temporal and spatial resolution. sensor. [0003] High-speed camera imaging based on pulsed light reflection or transmission can be used to observe fast physical phenomena. The latest application of ultrashor...

AI Technical Summary

Problems solved by technology

However, currently available high-speed 2D cameras are not sufficient for picosecond-scale pump-probe imaging, so 1D photodetectors are often used, and the state-of-the-art photodetectors have response times of several picoseconds

To achieve two-dimensional measurements with ultra-high temporal resolution, one-dimensional detection can be extended to two-dimensional imaging by deploying multiple photodetectors in a grid layout or sequentially scanning a single photodetector over the target area, but it can achieve The field of view is not large, and the imaging lateral resolution is low

At the same time, due to the light background noise of the camera exposure time, the contrast based on short-pulse pump-probe imaging is low, which limits the imaging quality of ultrafast kinetics and cannot achieve quantitative analysis.

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