Abstract

Cryogenic ultrastable laser cavities push laser stability to new levels due to their lower thermal noise limitation. Vibrational noise is one of the major obstacles to achieve a thermal-noise-limited cryogenic ultrastable laser system. Here, we carefully analyze the vibrational noise contribution to the laser frequency. We measure the vibrational noise from the top of the pulse-tube cryocooler down to the experiment space. Major differences emerge between room and cryogenic temperature operation. We cooled a homemade 6 cm sapphire optical resonator down to 3.4 K. Locking a 1064 nm laser to the resonator, we measure a frequency stability of . The vibration sensitivities change at different excitation frequencies. The vibrational noise analysis of the laser system paves the way for in situ accurate evaluation of vibrational noise for cryogenic systems. This may help in cryostat design and cryogenic precision measurements.

Highlights

  • Cryogenic-cavity-based ultrastable lasers are one of the most promising options for improving laser stability by reducing the thermal noise limit to 10−17 − 10−18 level [1,2,3,4,5,6,7]

  • We report in situ vibration measurements under cryogenic temperature, and successfully evaluate the vibrational noise contribution to a cryogenic ultrastable system

  • The in situ cryogenic vibration measurement right on top of the cryogenic plate clearly demonstrates the vibrational dynamics of the cryostat

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Summary

Introduction

Cryogenic-cavity-based ultrastable lasers are one of the most promising options for improving laser stability by reducing the thermal noise limit to 10−17 − 10−18 level [1,2,3,4,5,6,7]. We use an in situ, high resolution vibration measurement equipment (geophone) under cryogenic temperature to measure the vibration level of the sample holder of a closed-cycle cryostat. Driven by the requirement of the cryogenic ultrastable laser, we carry out vibrational measurements inside a specially designed vibration-reduction pulsetube cryostat by using the properly re-calibrated geophones. We built a cryogenic-cavity-based ultrastable laser system using this specially designed closed-cycle cryostat. The calculated vibrational noise contribution from the measured vibrations and the calibrated vibration sensitivity of the cavity matches well to the measured laser frequency noise. The technique developed paves the way for accurate in situ evaluation of vibrational noise for cryogenic systems, which can be great help for cryostat design and cryogenic precision measurements

Vibration Measurement of the Cryostat
Laser Stabilization and Vibration Noise Evaluation
Findings
Conclusions

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