A microrod-resonator Brillouin laser with 240 Hz absolute linewidth

Abstract

We demonstrate an ultralow-noise microrod-resonator based laser that oscillates on the gain supplied by the stimulated Brillouin scattering optical nonlinearity. Microresonator Brillouin lasers are known to offer an outstanding frequency noise floor, which is limited by fundamental thermal fluctuations. Here, we show experimental evidence that thermal effects also dominate the close-to-carrier frequency fluctuations. The 6-mm diameter microrod resonator used in our experiments has a large optical mode area of ~100 μm${}^2$, and hence its 10 ms thermal time constant filters the close-to-carrier optical frequency noise. The result is an absolute laser linewidth of 240 Hz with a corresponding white-frequency noise floor of 0.1 Hz${}^2$/Hz. We explain the steady-state performance of this laser by measurements of its operation state and of its mode detuning and lineshape. Our results highlight a mechanism for noise that is common to many microresonator devices due to the inherent coupling between intracavity power and mode frequency. We demonstrate the ability to reduce this noise through a feedback loop that stabilizes the intracavity power.

11 pages, 5 figures

References in corpus (5)

• LIGO: The Laser Interferometer Gravitational-Wave Observatory
• Brillouin Lasing with a CaF_2 Whispering Gallery Mode Resonator
• Low-Pump-Power, Low-Phase-Noise, and Microwave to Millimeter-wave Repetition Rate Operation in Microcombs
• Phase Steps and Hot Resonator Detuning in Microresonator Frequency Combs
• Noise and dynamics of stimulated Brillouin scattering microresonator lasers

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• Spectral purification of microwave signals with disciplined dissipative Kerr solitons
• Spatiotemporal mode-locking and photonic flywheel in multimode microresonators
• The Phonon-Limited-Linewidth of Brillouin Lasers at Cryogenic Temperatures
• Optically synchronized fiber links with spectrally pure integrated lasers
• Ultraprecise optical-frequency stabilization with heterogeneous III-V/Si lasers
• Microresonator Brillouin Laser Stabilization Using a Microfabricated Rubidium Cell
• Brillouin lasing in coupled silica toroid microcavities
• Relative Intensity Noise in a Multi-Stokes Brillouin Laser