Toothed iris diaphragm helps control radial intensity inside a femtosecond-laser filament core

Aug. 11, 2020
A “stellate” iris diaphragm controls intensity inside a filament, while drilling into a metal sheet characterizes filament beam shape.
2006 Lfw Nb Z05

Plasma-based filamentation can occur when an intense femtosecond laser pulse propagates in optically transparent media such as air. The phenomenon has found applications in imaging, microfabrication, remote sensing, water condensation, and triggering and guiding discharges, in which the radial distribution of laser fluence inside the filament core is crucial. However, directly measuring and controlling the fluence within a filament core (which is less than 100 μm in diameter) is still a challenge due to the extremely high intensity. Researchers from the Shanghai Institute of Optics and Fine Mechanics at the Chinese Academy of Sciences (CAS; Beijing) have demonstrated new ways to directly measure and successfully control the laser fluence inside a single filament core.

In the experiments, by examining filament-fabricated microstructures on materials, the radial fluence distribution across the filament core and its evolution along the filament were spatially resolved for the first time. Instead of using a traditional circular iris diaphragm, a stellate iris was introduced to suppress iris diffraction effects. As a result, a higher laser fluence and a denser plasma inside the filament cores were generated; this was further confirmed by measuring the radial fluence inside filament cores using the filaments to drill through 15-μm-thick aluminum sheets and then looking at the resulting holes. Experimental results are in agreement with numerical simulations obtained by solving the nonlinear Schrödinger equation. In addition to understanding the filamentation process and its control, the results may also be valuable for other filament-based laser applications such as rainmaking and lightning control. Reference: H. Guo et al., Opt. Express (2020); https://doi.org/10.1364/oe.392827.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Next generation tunable infrared lasers

Nov. 28, 2023
Discussion of more powerful and stable quantum cascade tunable infrared lasers, applications, and test results.

What AI demands mean for data centers

Nov. 28, 2023
The 2023 Photonics-Enabled Cloud Computing Summit assembled by Optica took an aggressive approach to calling out the limitations of today’s current technologies.

SLP feature for lighting control available on cameras offering

Nov. 28, 2023
A proprietary structured light projector (SLP) feature is now available on the company’s camera series, including the ace 2, boost R, ace U, and ace L.

Chroma Customer Spotlight - Dr. David Warshaw, About his Lab

Nov. 27, 2023
David Warshaw, Professor and Chair of Molecular Physiology and Biophysics at the University of Vermont (UVM), walks us through his lab. Learn about his lab’s work with the protein...

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!