Event
Ph.D. Research Proposal Exam: Xinyi Liu (Frederica Sorkin)
Friday, September 25, 2026
11:00 a.m.
IREAP
Souad Nejjar
301 405 8135
snejjar@umd.edu
ANNOUNCEMENT: Ph.D. Research Proposal Exam
Name: Xinyi Liu (Frederica Sorkin)
Committee:
Professor Howard Milchberg (Chair)
Professor Thomas Murphy
Professor Matthew Landreman
Date/time: Friday, September 25 at 11:00 AM
Location: IREAP
Title: Applications of High-Intensity Laser-Air Interactions: Remote Radiation Detection and Continuous Optical Waveguiding
Abstract: This research proposal explores fully optical schemes that address limitations of long-distance radiation detection and long-range atmospheric waveguiding of optical signals.
Conventional methods for remote detection of radioactive sources are heavily constrained by the rapid drop-off of the source’s decay flux over distance, either by scattering or geometry. We demonstrate the remote detection of α- and γ-radiation from radioactive Po-210 and Fe-55 sources via laser-driven avalanche breakdown at a standoff distance of 30 m using 100ns, l=10.6m laser pulses with 1 J pulse energy. The data shows statistically significant increases in breakdown probability when radiation sources are present, verifies observed radiation drop-off behavior with numerical calculations, and discusses the potential for further standoff distances and the detection of higher energy γ sources.
High-intensity laser-air interactions can also be used to imprint refractive index guiding structures in the air –femtosecond-filament-driven air waveguides– to mitigate the spreading of optical sources of interest such as diagnostic spectra or secondary laser beams. This proposal presents two ongoing quasi-steady state air waveguide experiments. We are using l=800nm, 40 fs, 12 mJ, Ti:Sapphire laser pulses in a TEM11 mode to form quad-filaments that generate a meter-scale continuous waveguide, guiding a 2 kW CW 1070 nm beam, the power of which is magnitudes higher than previously air-waveguided CW lasers. Additionally, we are using l=1030nm, 650 fs, 200 mJ, 1 kHz Yb:YAG laser pulses in a LG01 mode to form multi-filaments that generate a ~30 m long continuous waveguide, with the goal of guiding a 10 W l=1550 nm beam. Through these ongoing experiments, we aim to examine the effects of various degrees of thermal blooming within the air waveguide, as well as test the guiding of different wavelengths.
