Enhanced Radiation Hardness of InAs/GaAs Quantum Dot Lasers for Space Communication

Semiconductor lasers hold significant promise for space laser communication. However, excessive radiation in space can cause laser failures. In principle, quantum dot (QD) lasers are more radiation-resistant than traditional semiconductor lasers because of their superior carrier confinement and smaller active regions. However, the multifaceted nature of radiation effects on QDs result in ongoing controversies. In this work, comprehensive radiation tests under simulated space conditions on InAs/GaAs QDs and lasers is conducted to validate their performance. The results reveal that InAs/GaAs QDs with filling factors exceeding 50% exhibit enhanced radiation hardness. The linewidth enhancement factor (LEF) of well-designed QD lasers remains remarkably stable and nearly zero, even under proton irradiation at a maximum fluence of 7 × 10¹³ cm⁻², owing to their intrinsic insensitivity to irradiation-induced defects. These QD lasers demonstrate an exceptional average relative intensity noise (RIN) level of −162 dB Hz⁻¹, with only a 1 dB Hz⁻¹ increase at the highest fluence, indicating outstanding stability. Furthermore, the lasers exhibit remarkable robustness against optical feedback, sustaining stable performance even under a feedback strength as high as −3.1 dB. These results highlight the critical advantages of QD lasers for space laser communication applications, where high reliability and resilience to radiation and environmental perturbations are essential.