The effectiveness of amplitude modulation on the laser dazzling of a mid-infrared imager

Aviation is exceptionally vulnerable to man-portable missile attacks (MANPADS), particularly during the critical stages of flight, e.g., take-off and landing. Consequently, aircraft require a further means of self-protection in addition to pyrotechnic flares. Laser Directed Infrared Countermeasures (DIRCM) target the infrared guidance system present in the majority of all MANPADS, resulting in sensor dazzle and possible damage - a soft kill approach. Unfortunately, current DIRCM systems, albeit highly effective against first and second-generation seekers, are less against imaging ones (third and fourth-generation). Our paper investigates a means to increase the effectiveness of dazzle by modulating the laser at a rate close to the frame rate of the imaging sensor, i.e., a strobing effect. A continuous-wave quantum cascade laser (QCL) at 4.6 microns illuminated a mid-infrared focal plane array imager, modulated by either an optical chopper or by periodically varying the current of the QCL. The laser beam and a representative target were combined optically using plano and off-axis parabolic mirrors, resulting in the imager viewing a dazzled scene at infinity. In summary, we demonstrate experimentally that the intermittency of the laser dazzle could improve the effectiveness of a DIRCM system.