Filamentation in Atmospheric Air with Tunable 1100\u20132400\u2009nm Near-Infrared Femtosecond Laser Source

Sean P O’Connor,Vladislav V Yakovlev,Andrew W Wharmby,Adam R Boretsky,Christopher B Marble,Marlan O Scully,Gary D Noojin,Dawson T Nodurft

doi:10.1038/s41598-019-48542-1

Sean P O’Connor, Vladislav V Yakovlev + Show 6 more

Open Access

https://doi.org/10.1038/s41598-019-48542-1

Copy DOI

Abstract

Intense femtosecond pulse filamentation in open-air has been utilized for long distance optical communication and remote sensing, but it results in nonlinear-effect driven eye hazards which are not addressed by current eye safety standards. A systematic study of filamentation in atmospheric air was performed using a tunable 100 fs near-infrared laser (1100 nm–2400 nm). While undergoing filamentation, each source wavelength was spectrally broadened resulting in supercontinuum and third harmonic generation in the visible and near-IR spectrum. We record the spectra at the center and fringes of the supercontinuum as it is imaged onto a planar surface. In a full beam collection regime, we report the energy of the sub-1000 nm light generation for source wavelengths from 1100 nm to 1600 nm and compare the energy density to the maximum permissible exposure values under the ANSI Z136.1 laser safety standard.

Highlights

Laser induced filamentation is a nonlinear optical effect where intense laser pulses undergo self-focusing from the Kerr effect to overcome pulse diffraction and to propagate distances much larger than the diffraction length while maintaining a narrow beam diameter
We demonstrated that these near-IR wavelengths were able to generate a supercontinuum in the visible spectrum, as well as distinct third harmonics
These third harmonic peaks in the visible light spectrum demonstrate a clear laser-eye safety hazard according to the ANSI guidelines[23]

Summary

Introduction

Laser induced filamentation is a nonlinear optical effect where intense laser pulses undergo self-focusing from the Kerr effect to overcome pulse diffraction and to propagate distances much larger than the diffraction length while maintaining a narrow beam diameter. Concurrent studies of high harmonic generation in zinc selenide have shown the generation of sufficient visible and near-infrared radiation light from mid-IR source wavelengths to pose a retinal hazard by ANSI standards[24]. We demonstrate filamentation in atmospheric air in the lab with tunable near-infrared laser pulses with wavelengths ranging from 1100 nm to 2400 nm.

Results

Conclusion