Passive radiative cooling architecture for high-power optoelectronic packages

In high-power semiconductor lasers, efficient thermal management is crucial, particularly in compact transistor-outline (TO) can packages where heat dissipation is challenging. The conventional glass window used in these packages, though transparent in the visible regime, exhibits low thermal conductivity and infrared transparency, leading to heat accumulation, elevated junction temperatures, and degraded device performance. To overcome this limitation, we fabricated and optimized a thermally and optically transparent polyethylene (PE) film as a replacement for the commercial glass window. By tailoring its thickness to enhance mid-infrared transparency while maintaining optical transparency at 660 nm and mechanical strength, the 100-μm PE film enables efficient radiative cooling, resulting in a window temperature reduction of up to 9.4 °C compared to the glass configuration. This improvement yields, for instance, a reduced threshold current (54 mA reduction), increased output power (by ∼ 50 mW), and enhanced slope efficiency (0.11 W/A enhancement) at 35 °C and higher. At an ambient temperature of 80 °C, thermal fitting reveals an effective chip temperature of 72.8 °C, corresponding to a 7.2 °C cooling advantage over the glass-covered device. Our approach sustains optical modulation performance of ∼1.8-1.9 GHz modulation bandwidth and improves direct current optical orthogonal frequency-division multiplexing (DCO-OFDM) net data rate to 2.11 Gb/s. These results establish the PE film as a robust, low-cost, scalable, and effective thermal management solution for enhancing the performance and reliability of high-power optoelectronic devices in thermally constrained environments.