Spectral and temporal characteristics of air-plasma continuum generated by nanosecond laser at 355 nm

• Two broadband beams with almost the similar characteristics ranging from 400 nm to 700 nm are obtained
• The dominant process for the ions formation in air excited by Nd:YAG laser at 355 nm are mainly through a process of inverse bremsstrahlung.
• As laser energy increasing, the continuum width seems increase.
• For a given laser energy, the continuum pulse duration could be controlled by adjusting the collection point.

White continuum is generated from laser-induced air plasma by nanosecond laser at 355 nm. We investigate not only the spectral characteristics but also the temporal behavior of air plasma white continuum. The relationship between plasma spectra and laser energy density is explored, and the results show that a process of inverse bremsstrahlung type is the mechanism responsible for the breakdown. By adjusting the coupling angle between white continuum and optical fiber, the pulse duration can be controlled as short as ~10 ns. Furthermore, two nanosecond broadband beams with almost the similar characteristics ranging from 400 nm to 700 nm are obtained, which can be employed in transient absorption spectroscopy study.