Confocal Laser Induced fluorescence diagnostic with annular laser beam for large focal distances

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Non-Confidential Brief

Confocal Laser Induced Fluorescence Diagnostic With Annular Laser Beam for Large Focal Distances

Princeton Docket # 23-4006-1

Laser induced fluorescence (LIF) is routinely used for characterization of plasma sources or in gas dynamic applications. Conventional LIF techniques require access to studied volume from two sides: for the laser beam injection and in perpendicular direction for the fluorescence emission collection. This limits the applicability of these techniques in some cases, as it is not possible to provide the required optical access. Confocal LIF design, when laser beam injection and collection paths coincide, helps to overcome this issue, however, such approach results in reduced spatial localization of the measurements. 

Researchers at the Princeton Plasma Physics Laboratory have proposed a design in which the laser beam of annular shape is used, which achieves spatial localization comparable with conventional methods and offers high signal-to-noise ratio. The current design can be implemented with a free space laser beam or coupled with a vacuum chamber through the fiber. This invention can be used for characterization of plasma or gas processes in environments with limited optical access relevant for many industrial applications, such as microelectronic production, aerospace, etc.


  • Remote diagnostics of plasma in scientific or industrial applications with limited optical access
    • Microelectronics
  • Combustion and gas dynamic processes


  • Annular shape of the laser beam achieves high spatial localization of the measurement along the optical access
  • High signal-to-noise ratio compared to other confocal methods


Ivan Romadanov is an Associate Research Physicist at Princeton Plasma Physics Laboratory. He earned his Ph.D. in Physics from the University of Saskatchewan (2019) and his M.Eng. in Mechanical and Aerospace Engineering from Bauman Moscow State Technical University (2009). His research focuses on low-temperature plasma physics, with applications in plasma manufacturing, diagnostic methods, and space propulsion. He has conducted research on turbulent processes in plasma sources, methods of their control, and diagnostics. Additionally, he has expertise in x-ray imaging, particularly for cancer treatment, and has conducted both experimental and theoretical work on dual-energy x-ray imaging.

Intellectual Property Status
Patent protection is pending.

Princeton is currently seeking commercial partners for the further development and commercialization of this opportunity. 

Chris Wright

Princeton University Office of Technology Licensing • (609) 258-6762•

Laurie Bagley

Princeton Plasma Physics Laboratory • (609) 243-2425•

Patent Information:
For Information, Contact:
Chris Wright
Licensing Associate
Princeton University
Yevgeny Raitses
Ivan Romadanov