Case Study: Feasibility of New Technologies
Disruption of laser propagation
High energy ultrashort pulse lasers (USPLs) are able to induce a number of optical and physical phenomena hitherto not possible with continuous wave (CW) or more conventional (e.g. Q-switched) pulsed lasers. This has in turn paved the way for a host of potential novel effects and applications. We were engaged by BAE Systems – Air in the UK to investigate the possibility of using USPLs to disrupt the propagation and effectiveness of other lasers. Using our practical experience in experiment design and construction as well as subject matter knowledge in USPL-induced “filamentation”, we were able to propose and undertake a program of work to explore this both theoretically and experimentally. Filamentation refers to the extended plasma structures generated in air when a USPL pulse experiences alternating beam focusing and de-focusing from the nonlinear Kerr effect and ionisation respectively. The plasma generated by this phenomenon causes a significant refractive index change to the air it travels through and this change persists over a period much longer than the period of the USPL pulse train. The laser filament bundle is seen as a blueish-white streak below:
USPL-induced filament seen as a white-purple streak.
Experiment designed by LumOptica and set up at SCAPA facility, University of Strathclyde. USPL laser propagating from far end; CW probe beam travelling in opposite direction and with crossing angle at midpoint.
Using such facilities, it is imperative that time is well-spent, with a fixed test schedule available. Through careful planning, de-risking tests in our own labs and risk mitigation we were able to achieve all the project objectives and demonstrated major beam disruption. As always, we kept our customer fully appraised of progress at all stages and even invited them to the SCAPA labs to demonstrate the effect in person! The experimental data was used to validate and refine the model, which was then used to provide numerical predictions at more interesting scales.
The results were presented at the SPIE Sensors + Imaging 2023 conference. A screenshot showing the disruptive effects of overlapping a filament bundle with a CW laser (red) with is shown below…
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