Microcontroller-based pulse coding of quantum cascade lasers for infrared countermeasures and communication

Precise control of Quantum Cascade Laser (QCL) modulation is essential for both directed infrared countermeasure (DIRCM) systems and covert free-space optical communication. We present a compact, microcontroller driven modulation unit that enables real-time adjustment of frequency, duty cycle, phase, and waveform in a 4.56 μm QCL. Experiments with a cooled InSb focal plane array (FPA) reveal two distinct dazzling regimes: (i) long integration times dominated by optical saturation of the illuminated spot, and (ii) short integration times where global horizontal bands emerge from rail loading and bias collapse in the Direct Injection (DI) readout circuit. The number of bands scales predictably with modulation-to-frame-rate ratio (N ≈ fm/ff ), and their contrast depends on integration time. These controllable ROIC-induced artifacts can be exploited to disrupt imaging seekers or to encode structured communication patterns.