Nano-Kelvin thermometry and temperature control: beyond the thermal noise limit

Abstract

We demonstrate thermometry with a resolution of 80 $\mathrm{nK}/\sqrt{\mathrm{Hz}}$ using an isotropic crystalline whispering-gallery mode resonator based on a dichroic dual-mode technique. We simultaneously excite two modes that have a mode frequency ratio very close to two ($\pm 0.3$ppm). The wavelength- and temperature-dependence of the refractive index means that the frequency difference between these modes is an ultra-sensitive proxy of the resonator temperature. This approach to temperature sensing automatically suppresses sensitivity to thermal expansion and vibrationally induced changes of the resonator. We also demonstrate active suppression of temperature fluctuations in the resonator by controlling the intensity of the driving laser. The residual temperature fluctuations are shown to be below the limits set by fundamental thermodynamic fluctuations of the resonator material.

References in corpus (4)

• Temperature measurement and stabilization in a birefringent whispering gallery resonator
• CaF2 Whispering-Gallery-Mode Resonator Stabilized Narrow Linewidth Laser
• Frequency stability of a dual-mode whispering gallery mode optical reference cavity
• Photothermal Fluctuations as a Fundamental Limit to Low-Frequency Squeezing in a Degenerate Optical Parametric Amplifier

Cited by in corpus (2)

• High-Q silk fibroin whispering gallery microresonator
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