The Quantum Limits of Laser Linewidth

OEwaves is proud to announce that our CEO, Lute Maleki, together with Andrey Matsko of NASA’s Jet Propulsion Laboratory (JPL), has published groundbreaking new research in Optics Letters. Their paper, “Quantum linewidth limitation of a laser stabilized with a nonlinear microcavity” [Opt. Lett. 49, 4879–4882 (2024)] explores the fundamental physics that define how stable a laser can ultimately become.

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In this work, Maleki and Matsko investigate what happens when a laser is locked to an optical cavity with nonzero optical cubic nonlinearity. They demonstrate that the ultimate linewidth of such a laser is restricted by the nonlinear frequency shift produced per single photon localized in the cavity mode. While this quantum effect exists, in practical monolithic microcavities it is largely masked by fundamental thermodynamic noise.

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The authors propose an experimental approach for revealing this quantum limit: using two independent lasers, each locked to spatially overlapping modes of the same nonlinear resonator. This method could provide a direct measurement of the quantum linewidth limitation in realistic systems.

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The implications of this research are significant. Understanding the quantum limits of linewidth stability is critical for advancing laser performance in applications that demand extreme precision, from quantum sensing and atomic clocks to optical communications and fundamental physics experiments. This publication adds to OEwaves’ long history of pioneering work in ultra-low-noise lasers, whispering-gallery-mode resonators, and photonic innovation, highlighting our commitment to pushing the boundaries of what’s possible in optical science and technology.

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Read the full paper here: Quantum linewidth limitation of a laser stabilized with a nonlinear microcavity.