Wavelength-tuned stability in high-radiance diode laser-sustained plasma sources

Laser-sustained plasma (LSP) light sources often suffer from severe plasma drift and expansion when increasing brightness. This makes it difficult to balance high brightness and high stability, which limits their application in precision fields such as semiconductor inspection. To address this key bottleneck, this paper proposes and validates a novel dual-parameter control method that enables regulation of the energy injection and energy deposition depth in LSP. This strategy exploits two intrinsic properties: the temperature-induced wavelength redshift of a fiber-coupled diode laser (0.42 nm/°C) and the strong bound-bound absorption of xenon plasma near 976 nm. By adjusting the operating current and temperature, precise control over the LSP emission characteristics, spatial position, and stability is achieved. Results show that increasing the current alone (5 → 10 A, 25 °C) expands the radiation area by 110.90%, induces a centroid drift of 126.14 μm, and causes significant instability. In contrast, adjusting the temperature alone (25 → 35 °C, 6 A) produces a small displacement of only 18.43 μm and an area change of 9.32%, with almost no loss in stability. Based on these findings, the proposed power-wavelength synergistic control strategy shifts the current-induced centroid drift back by 41.35% while maintaining high radiation intensity. A sub-micrometer positioning step resolution (∼0.03 μm) of the plasma centroid is achieved, enabled by the ±0.01 °C temperature control precision. This study breaks through the bottleneck of traditional single-parameter tuning and provides a simple yet efficient solution for high-brightness, high-stability LSP light sources.