Long-term stable optical cavity for special relativity tests in space

Abstract

BOOST (BOOst Symmetry Test) is a proposed space mission to search for Lorentz invariance violations and aims to improve the Kennedy-Thorndike parameter constraint by two orders of magnitude. The mission consists of comparing two optical frequency references of different nature, an optical cavity and a hyperfine transition in molecular iodine, in a low Earth orbit. Naturally, the stability of the frequency references at the orbit period of 5400 s (f =0.18 mHz) is essential for the mission success. Here we present our experimental efforts to achieve the required fractional frequency stability of 7.4 × 10 −14 Hz −1/2 at 0.18 mHz (in units of the square root of the power spectral density), using a high-finesse optical cavity. We have demonstrated a frequency stability of (9 ± 3) × 10 −14 Hz −1/2 at 0.18 mHz, which corresponds to an Allan deviation of 10 −14 at 5400 s. A thorough noise source breakdown is presented, which allows us to identify the critical aspects to consider for a future space-qualified optical cavity for BOOST. The major noise contributor at sub-milli-Hertz frequency was related to intensity fluctuations, followed by thermal noise and beam pointing. Other noise sources had a negligible effect on the frequency stability, including temperature fluctuations, which were strongly attenuated by a five-layer thermal shield.

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

“…If integrating over longer times, these fluctuations, caused by thermal or mechanical stress, impact the achievable stability. To increase the long-term stability, efforts have been undertaken to reduce the impact of outside effects, such as by the choice of spacer material [249] and length of spacer, enclosure in thermal shields [113], or cryogenic environments [250]. The latter is especially interesting in groundbased experimental systems, such as for instance in [251].…”

“…For reasons of seismic and thermal insulation, these are typically neither robust nor compact. Therefore, the further development of these devices was identified by the community as an important challenge [109][110][111] and supported, e.g., by ESA activities [112][113][114] and is -with demonstrated fractional frequency instabilities significantly below 10 −15 -on a good path. As ultrastable laser systems have numerous applications beyond optical frequency standards, e.g., in atom interferometry, ultra-stable microwave generation, or optical telecommunication, the continued support of these activities is of high importance.…”

Enhanced Frequency noise suppression for LISA by combining cavity and arm locking control systems

“…Instead, the absolute ranging system based on PRN ranging is relied on, requiring only 6300 s (∼ 1.75 hours) of data to get a sufficiently accurate estimate of the Doppler trends. Cavity performance that approach the thermal limit [4,28] will significantly reduce residual noise, allowing Doppler parameter estimates to converge within 1500 s (∼ 0.5 hour) using the interferometer response only. These estimates (using either approach), can populate the phasemeter with a model estimate of the Doppler shifts based on Section III B.…”

“…The FP cavity estimation method described in Appendix A of [15], has a residual noise derived from the cavity noise coupled through an open arm sensor. For this calculation, we make two estimates of Doppler error based on two levels of cavity residual errors: 1) the cavity residual given in Equation A9, which is a conservative estimate, 2) the cavity residual such as in GRACE-FO [4] or in [28], that approach the cavity thermal noise limit (TNL) [29], modelled as…”

Thermal noise-limited laser stabilization to an 8 mL volume Fabry-Pérot reference cavity with microfabricated mirrors

“…This level of performance is achieved by exploiting large cavity mode volumes and/or cryogenic operation, relegating their use to well-controlled laboratory environments. However, there are a growing number of applications that demand compact, portable systems capable of low-noise operation in diverse and unpredictable environments, ranging from groundbased geodesy 15,16 and earthquake detection 17 to space-based tests of fundamental physics 18 . For these applications, significant scientific and technical impact can be achieved with laser instability at least an order of magnitude better than what is achievable either with an unlocked laser or with a system locked to a microwave oscillator; in other words, with laser fractional instability below 10 −14 for timescales up to ≈ 1 second.…”