Technical Papers and Presentations

Here we present a simulation for evaluation of novel obscurant candidates under high-energy laser (HEL) illumination. This approach incorporates thermal modeling into obscurant characterization, allowing for evaluation of the temperature increase of the candidate obscurants as well as temperature induced change in their scattering behavior. For ease of use, we built a custom graphical user interface (GUI) that allows a user to perform this analysis without specialized simulation knowledge. The only inputs required are a CAD file of the obscurant geometry and the material properties. We present simulated results for several scatterers that demonstrate the necessity of a multiphysics simulation approach.

The mitigation of high energy laser radiation (HEL) is important for the protection of various assets from an adversarial laser threat. A recent push in obscurant technologies has been the development of novel materials and novel geometries that exhibit customizable spectral features. To properly characterize these obscurants response to HEL illumination, both their electromagnetic and thermal behavior must be accounted for.

To accomplish this we used COMSOL Multiphysics and both the Electromagnetic Waves, Frequency Domain and Heat Transfer in Solids interfaces. These two interfaces allow evaluation of the particle’s behavior, such as its steady state temperature, for a given intensity illumination. The magnitude of the incident wave was then swept. Because the material properties of the obscurant may be temperature dependent, this approach also allows for determination of temperature dependent absorption (ACS), scattering (SCS), and extinction cross sections (ECS) for the obscurant.

Our custom interface includes a default sphere geometry and a small library of materials. However, a user can import their own geometry and customize their materials and calculations to fit their needs using simple buttons and menus. The GUI also displays plots and graphs for the user to analyze their results.

To demonstrate the utility of this modeling approach, Fig 1 shows the anticipated temperature of an Au nanorod and a Si sphere, both optimized for a high ECS to weight at a wavelength of 1.064 µm. In a pure electromagnetic analysis, the ECS to weight ratio of the Au nanoparticle is over four times larger than that of the Si sphere, suggesting that it is the “better” obscurant. However, the multiphysics simulation shows that the nanorod temperature will approach its melting point near 0.33 W/cm², a power level that can be achieved with off the shelf lasers, whereas the Si sphere will still be at room temperature. This demonstrates the necessity of incorporating multiphysics simulation in the obscurant design.