Experimental Study of PWM-Controlled Emission From a Large-Aperture VCSEL

This study demonstrates the use of pulse-width modulation (PWM) for mode selection in a large-aperture vertical-cavity surface-emitting laser (VCSEL). Experimental results reveal that driving the device with 1 kHz PWM pulses maintains a stable far-field pattern (FFP) and causes only negligible spectral drift. Increasing the PWM frequency up to 1 MHz redistributes the FFP from higher-order, donut-like transverse modes toward a centrally peaked, Gaussian-like mode, and shifts the dominant longitudinal resonance to shorter wavelengths. Encircled energy analysis quantifies these changes and confirms that PWM enables fine spatial and spectral emission control of the selected large-aperture VCSEL device. The results position PWM as a cost-effective and straightforward lever for dynamic VCSEL emission management.