Turbulence-free interference induced by the turbulence itself

Thomas A Smith,Yanhua Shih

doi:10.1063/5.0031474

Abstract

When a laser beam is incident on a double-slit interferometer without turbulence, the classic Young’s double-slit interference is present in the first-order measurement of the mean photon number (or intensity), while the second-order measurement of photon number fluctuation correlation (or intensity fluctuation correlation) yields a trivial constant. When optical turbulence is introduced, it destroys the classic interference present in the measurement of the photon number; however, two-photon interference appears in the measurement of photon number fluctuation correlation. This interesting observation means that the observed two-photon interference is not only observable through turbulence, i.e., turbulence-free, but also induced by the turbulence itself. Turbulence-free two-photon interference induced by the turbulence itself allows for interferometric sensing through strong turbulence when coherent radiation, such as a laser, is applied.

Highlights

Interferometers are powerful tools that utilize the superposition of radiation fields to execute precise and sensitive measurements
We reported a turbulence-free double-slit interferometer, inspired by the Hanbury Brown–Twiss interferometer,7,8,14 in which an incoherent thermal field was able to produce a turbulence-free two-photon interference pattern from the second-order measurement of photon number fluctuation correlation (PNFC) ⟨Δn1Δn2⟩, or intensity fluctuation correlation ⟨ΔI1ΔI2⟩, while no classic interference was observable from the first-order measurement of mean intensities ⟨I1⟩ and ⟨I2⟩
Different from thermal fields, which are a collection of a large number of distinguishable photons in a mixed state, a coherent field is a collection of a large number of indistinguishable photons in a pure state

Summary

Introduction

Interferometers are powerful tools that utilize the superposition of radiation fields to execute precise and sensitive measurements.1–6. We reported a turbulence-free double-slit interferometer, inspired by the Hanbury Brown–Twiss interferometer,7,8,14 in which an incoherent thermal field was able to produce a turbulence-free two-photon interference pattern from the second-order measurement of photon number fluctuation correlation (PNFC) ⟨Δn1Δn2⟩, or intensity fluctuation correlation ⟨ΔI1ΔI2⟩, while no classic interference was observable from the first-order measurement of mean intensities ⟨I1⟩ and ⟨I2⟩.16,17 Can we observe turbulence-free interference from an interferometer that employs the coherent laser beam as the light source?

Results

Conclusion