Estimating the phase in ground-based interferometry: performance comparison between single-mode and multimode schemes

TL;DR

This paper compares single-mode and multimode interferometry for phase estimation, showing single-mode often outperforms multimode in high flux and poor adaptive optics conditions, with specific advantages in robustness and performance.

Contribution

It provides a theoretical framework for phase error analysis and demonstrates the conditions under which single-mode interferometry surpasses multimode schemes.

Findings

Single-mode interferometry performs better in high flux regimes.

Single-mode is more robust to atmospheric turbulence.

Multimode performs slightly better in low light, detector noise regimes.

Abstract

In this paper we compare the performance of multi and single-mode interferometry for the estimation of the phase of the complex visibility. We provide a theoretical description of the interferometric signal which enables to derive the phase error in presence of detector, photon and atmospheric noises, for both multi and single-mode cases. We show that, despite the loss of flux occurring when injecting the light in the single-mode component (i.e. single-mode fibers, integrated optics), the spatial filtering properties of such single-mode devices often enable higher performance than multimode concepts. In the high flux regime speckle noise dominated, single-mode interferometry is always more efficient, and its performance is significantly better when the correction provided by adaptive optics becomes poor, by a factor of 2 and more when the Strehl ratio is lower than 10%. In low light level cases (detector noise regime), multimode interferometry reaches better performance, yet the gain never exceeds 20%, which corresponds to the percentage of photon loss due to the injection in the guides. Besides, we demonstrate that single-mode interferometry is also more robust to the turbulence in both cases of fringe tracking and phase referencing, at the exception of narrow field of views (<1 arcsec).