NM06 – Modelling an Acousto-Optic Beam Shaping Device for a DIRCM Laser Laboratory Setup

Directed Infrared Counter Measure (DIRCM) laser laboratory setups are used to mimic the real life DIRCM system and IR heat-seeking missile engagement scenarios in isolated laboratory environments. Typically, the output beam of a mid-infrared (Mid-IR) laser source is modulated in time using an acousto-optic (AO) modulator (AOM). Following the AOM in the optical path, within a distance of few meters, the laser beam is expanded and collimated, using traditional methods to have almost a uniform intensity profile at the target aperture [1, 2]. The whole process results in the simulation of the engagement of a countermeasure laser with an IR heat-seeking missile on an optical table. AO devices, besides their common usage of modulation, can also be used to transform a given laser beam profile into various other beam profiles [3]. By applying an RF signal consisting of multiple frequency components to an AO device, diffraction occurs into multiple orders. By this way, various beam profiles can be obtained along the optical path. In this study, we analyze the usage of an AO device in order to have an expanded beam profile with a uniform intensity distribution at few meters away from the laser source that is enough to cover an IR seeker’s aperture. With the use of an AO device for beam shaping, we aim to alleviate the need of costly and complex optical setups. The analysis is made in two dimensions using a numerical simulation software, which employs the finite element method with appropriate boundary conditions.