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Temperature-insensitive tunable and stable Fabry-Perot cavity for atomic physics

Joshua Ruelle, Martin Hauden, Francisco S. Ponciano-Ojeda, Marion Delehaye

Abstract

Optical Fabry-Perot cavities are crucial tools for metrology experiments, where they achieve extreme length stability, and for some atomic physics experiments, where tunability to atomic transitions enables atom-light interactions. However, achieving both frequency stability and tunability in a single cavity has remained a challenge, forcing metrology experiments exploiting atom-cavity interactions to rely on external active feedback systems to stabilize the length of the cavity. Here, we describe a piezoelectrically-tunable cavity with a cancellation of the coefficient of thermal expansion at around $5^\circ\mathrm{C}$, achieving fractional frequency instabilities at the $4\times 10^{-13}$ level for 1~s integration time. This advance eliminates the need for external stabilization in many atom-cavity experiments, making this design ideal for applications such as ultra-stable superradiant lasers and other cavity quantum electrodynamics experiments.

Temperature-insensitive tunable and stable Fabry-Perot cavity for atomic physics

Abstract

Optical Fabry-Perot cavities are crucial tools for metrology experiments, where they achieve extreme length stability, and for some atomic physics experiments, where tunability to atomic transitions enables atom-light interactions. However, achieving both frequency stability and tunability in a single cavity has remained a challenge, forcing metrology experiments exploiting atom-cavity interactions to rely on external active feedback systems to stabilize the length of the cavity. Here, we describe a piezoelectrically-tunable cavity with a cancellation of the coefficient of thermal expansion at around , achieving fractional frequency instabilities at the level for 1~s integration time. This advance eliminates the need for external stabilization in many atom-cavity experiments, making this design ideal for applications such as ultra-stable superradiant lasers and other cavity quantum electrodynamics experiments.
Paper Structure (11 sections, 1 equation, 4 figures)

This paper contains 11 sections, 1 equation, 4 figures.

Table of Contents

  1. Introduction
  2. Composite cavity design
  3. Methods
  4. Performances
  5. Finesse measurement
  6. Noise induced by PZT actuators
  7. Temperature control
  8. Coefficient of thermal expansion
  9. Stabilities
  10. Conclusion
  11. Funding information

Figures (4)

  • Figure 1: 3D representation of the tunable Fabry-Perot cavity consisting of a 50-mm long Zerodur spacer and mirrors stacked on a PZT ring and a Kovar washer.
  • Figure 2: Schematic side-view of the cavity vacuum chamber.
  • Figure 3: Cavity coefficient of thermal expansion measured by applying temperature steps to the cavity temperature set-point and measuring the subsequent changes in the 578nm laser frequency. A zero-crossing point is extracted at 4.9±0.5℃. Error bars are discussed in the main text.
  • Figure 4: Fractional frequency stability of the tunable cavity measured against the H-maser, estimated using the unbiased Allan deviation under several conditions. Quiet environment (ie atomic oven off): regulated at $T_0$ with PZTs disconnected (pink stars), regulated at $T_0$ with filtered PZTs (purple squares), and regulated at $T_0$ with non-filtered PZTs at 1V (green diamonds). Real operating conditions (atomic oven on): with PZTs disconnected at $T_0$ (blue lower triangles) and at room temperature (red upper triangles). Grey curve: fractional frequency stability of the H-maser measured against an ultra-stable cavity. Inset: unbiased Hadamard deviation of the same datasets, indicating the flicker frequency noise floor that could be achieved by suppressing frequency drift.