Mid-IR laser plays a significant role in ultrafast spectroscopy and strong-field experiments and have continuously attracted a great deal of interest, both scientifically and technologically. In this scenario, the accurate characterization of ultrashort mid-IR pulses is very essential and necessary to further the potential applications of these long wavelength laser sources.

Recently, researchers from Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences (CAS) proposed a new initial guess in PCGPA. The study was based on second-harmonic-generation frequency-resolved optical gating (SHG-FROG) technique, and the SHG-FROG device can be used for accurately characterizing ultrashort pulse in the mid-IR. The results were published on Optics and Laser Technology.

In their experiment, a mid-infrared pulse at 3580 nm from the home-built optical parametric amplifier (OPA) system was measured with a good agreement between the retrieved and measured spectrums. Different initial guesses were studied, and the spectrum retrieved by the proposed method was closer to the measured spectrum in spectrum shape and bandwidth.

Moreover, a further verification was made to compare the measured spectral phase difference with the calculated one by inserting a dispersion plate. The excellent phase agreement verified the accuracy of the measurement and high reliability of the device.

This initial guess with constraint both in time and frequency domain outperforms other guesses for the data errors analysis in these SHG-FROG apparatus. Therefore, it is capable of providing powerful support on dispersion compensation in the mid-IR.

This work is funded by the Strategic Priority Research Program of the Chinese Academy of Sciences; the National Natural Science Foundation of China; International S&T Cooperation Program of China; the Innovative Research Group of the National Natural Science Foundation of China.

Figure. The spectra retrieved by PCGPA.(Image by SIOM)

https://www.sciencedirect.com/science/article/pii/S0030399219302154

Contact:
Mr. Cao Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS
Email: caoyong@siom.ac.cn