Ultrashort laser pulse measurement device based on frequency resolved optical gating (FROG ) method

Abstract

The invention relates to an ultrashort laser pulse measurement device built based on a frequency resolved optical gating (FROG) method. The principle of the device is as follows: modification is performed on the basis of a standard FROG device, and a sinusoidal signal output by a signal generator is used for synchronously driving a voice coil motor and a scanning galvanometer. The voice coil motordrives a corner cube mirror to move to and fro so as to achieve quick delayed scanning, and the scanning galvanometer swings up and down and thus the spectrum of an autocorrelation signal expanded bygrating in a horizontal direction can be reflected to different positions on the light-sensitive surface of an area-array camera (CCD or CMOS) according to a delay sequence. Therefore, the area-arraycamera is continuously exposed within the half of a sinusoidal wave period, so that the complete FROG trace map can be shot, and then the measured pulse is reconstructed according to the FROG trace map.

Description

technical field [0001] The invention relates to the field of laser measuring equipment, more specifically, to an ultrashort laser pulse measuring device based on a frequency-resolved optical switch method. Background technique [0002] Ultrashort laser pulses have important applications in photochemistry, quantum coherence control, microscopic imaging, optical communication, micromachining and other fields, and the measurement of ultrashort laser pulses is becoming more and more important. Currently, ultrashort laser pulses are measured using Frequency-resolved optical switching method (FROG). [0003] The frequency-resolved optical switching method is a general method for measuring ultrashort laser pulses. The subsequent pulse reflects itself in the spectrum it forms), because the spectrum is a function of the delay time between two pulses, and the relevant information of the pulse can be extracted from the FROG record of the pulse using a two-dimensional phase recovery al...

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Problems solved by technology

However, a major disadvantage of the standard FROG device is that the shooting time is long, resulting in slow measurement speed. For example, it usually takes more than 1 minute to take a large matrix spectrogram (1024×1024)

[0006] ②Single-shot FROG device: The pulsed light is divided into two beams after being expanded by double mirrors, and then converged on the frequency doubling crystal at a specific angle through the cylindrical mirror to form a corresponding relationship between time delay and spatial coordinates, so no scanning is required Delay, because there is no need for scanning delay, two-dimensional FROG trace can be obtained at one time, so the measurement speed is very fast, especially suitable for ultrashort pulses with low pulse repetition rate (1Hz~1kHz); but its disadvantage is sensitivity 2-3 orders of magnitude lower than standard FROG, usually only strong pulses can be measured, and the measurement range of pulse width is limited

[0007] ③GRENOUILLE device: GRENOUILLE replaces the commonly used complex beam splitter / delay line / beam recombination optical device with a Fresnel double prism. The Fresnel double prism is composed of two identical thin triangular prisms. The optical components of the Fresnel double prism can obtain two beams of coherent light to achieve light interference, so no scanning delay is required, the measurement speed is fast, and the sensitivity is high; but each device can only measure a fixed bandwidth, pulse Ultrashort pulses in a wide and wavelength range for narrow measurement ranges

[0010] The standard FROG device takes a 1-dimensional spectrum step by step, and cannot use a large area array camera to achieve fast pulse measurement; although Single-shot FROG and GRENOUILLE can use a large area array camera, the shooting speed is very fast, but their scope of application is relatively small. narrow

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