2024
Research News
Narrow-linewidth Lasers Overcome Noise Challenges for Next-Gen Applications
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Researchers from Changchun Institute of Optics, Fine Mechanics, and Physics of the Chinese Academy of Sciences enhanced the performance of narrow-linewidth semiconductor lasers by overcoming challenges in reducing noise for their high-precision applications. The study was published in Heliyon.
Semiconductor lasers with narrow linewidths are crucial for high-performance systems due to their high spectral purity and frequency stability. However, noise, manifested as phase, intensity, and frequency fluctuations, limits their performance. In optical communication, excessive noise can degrade signal quality and bandwidth, while in sensing systems, it affects accuracy and reliability.
In this study, researchers conducted a comprehensive review of noise sources in semiconductor lasers, including spontaneous emission and carrier density fluctuations. They analyzed existing noise suppression techniques focusing on material optimization, cavity structure improvements, and feedback control mechanisms. Key efforts included designing advanced epitaxial structures, integrating Bragg gratings for mode stability, and leveraging external cavity feedback to reduce noise power.
For measuring noise, researchers compared methods like direct relative intensity noise (RIN) detection and phase discrimination, highlighting the trade-offs between the practicality and the precision. They also improved waveguide structures such as buried heterostructures (BHs) using cutting-edge fabrication techniques, enhancing the optical and carrier confinement.
The implementation of BH structures reduced relative intensity noise to levels as low as -170 dBc/Hz. The optimized external feedback mechanisms enabled linewidth narrowing to less than 100 Hz, significantly enhancing spectral purity. The advanced designs for waveguides and quantum well configurations achieved a delicate balance between low noise and high output power. These promise more reliable lasers with reduced thermal and shot noise effects. These advancements set the stage for next-generation laser applications.
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