Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing

• Published in: Journal of visualized experiments no. 146
• Main Authors: Springer, Matthews M, Strycker, Benjamin D, Wang, Kai, Sokolov, Alexei V, Scully, Marlan O
• Format: Journal Article
• Language: English
• Published: United States 25-04-2019
• Subjects: Amplifiers, Electronic; Lasers; Optical Imaging - instrumentation; Remote Sensing Technology - instrumentation; Spectrum Analysis
• ISSN: 1940-087X
• DOI: 10.3791/58207

Probing remote matter with laser light is a ubiquitous technique used in circumstances as diverse as laser-induced breakdown spectroscopy and barcode scanners. In classical optics, the intensity that can be brought to bear on a remote target is limited by the spot size of the laser at the distance of the target. This spot size has a lower bound determined by the diffraction limit of classical optics. However, amplified femtosecond laser pulses generate intensity sufficient to modify the refractive index of the ambient air and undergo self-focusing. This self-focusing effect leads to the generation of highly intense laser filaments which maintain their intensity and small sub-millimeter diameter size at distances well beyond the classical Rayleigh length. Such intensity provides the capability of remote scanning, imaging, sensing, and spectroscopy with enhanced spatial resolution. We describe a technique for generating filaments with a femtosecond regenerative chirped-pulse amplifier, and for using the resulting filament to conduct imaging and spectroscopic measurements at remote distances of at least several meters.