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 5f1f29684d9ef

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

Advancing Neuroscience Using High-Precision 3D Printing

March 7, 2025
Learn how Cold Spring Harbor Laboratory Used High-Precision 3D Printing to Advance Neuroscience Research using 3D Printed Optical Drives.

From Prototyping to Production: How High-Precision 3D Printing is Reinventing Electronics Manufacturing

March 7, 2025
Learn how micro 3D printing is enabling miniaturization. As products get smaller the challenge to manufacture small parts increases.

Sputtered Thin-film Coatings

Feb. 27, 2025
Optical thin-film coatings can be deposited by a variety of methods. Learn about 2 traditional methods and a deposition process called sputtering.

What are Notch Filters?

Feb. 27, 2025
Notch filters are ideal for applications that require nearly complete rejection of a laser line while passing as much non-laser light as possible.

Voice your opinion!

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