Improving localization precision of Brillouin measurements using spectral autocorrelation analysis

Eitan Edrei,Giuliano Scarcelli,Milos Nikolic

doi:10.1142/s1793545817420044

Eitan Edrei, Giuliano Scarcelli + Show 1 more

Open Access

https://doi.org/10.1142/s1793545817420044

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Abstract

Brillouin spectroscopy is a powerful tool for measuring the mechanical properties of materials without contact. The sensitivity to mechanical changes that a Brillouin spectrometer can detect is determined by the precision to which a spectral peak can be localized. The localization precision is however fundamentally limited by the low number of photons within a Brillouin measurement, as well as by intrinsic noise of the setup. Here, we present a method to improve the spectral sensitivity of Brillouin measurements by exploiting the autocorrelation function of the spectrum. We show that by performing a localization process on the autocorrelation function nearly 20% increase in localization precision can be obtained. This result is consistent between our theoretical treatment, numerical simulation and experimental results. We further study the effect of background noise on the precision improvement for realistic scenarios.

Highlights

Brillouin spectrometer utilizes a scanning interferometer featuring Fabry–perot etalons[3,4,5]; in recent years the introduction of a virtual image phased array (VIPA) etalons[6] and tilted geometry has dramatically enhanced the throughput of the spectrometer and allowed the acquisition of the entire Brillouin spectrum in one shot.[7]
The precision to which an optical signal can be spatially localized has been studied for many years,[30] and is the underlying principle for superresolution localization microscopy techniques such as PALM35 and STORM.[36]
Brillouin spectroscopy uses this type of localization process achieving spectral sensitivities that are much higher than the nominal spectral resolution of the spectrometer

Summary

Introduction

Brillouin light scattering has been used for many years to measure viscoelastic properties of materials without contact.[1,2] Traditionally, Brillouin spectrometer utilizes a scanning interferometer featuring Fabry–perot etalons[3,4,5]; in recent years the introduction of a virtual image phased array (VIPA) etalons[6] and tilted geometry has dramatically enhanced the throughput of the spectrometer and allowed the acquisition of the entire Brillouin spectrum in one shot.[7]. Di®erent approaches to this challenge have been pursued: on one hand stimulated scattering interaction[19,20] or multiplexed congurations[21] have been demonstrated; on the other hand, an ongoing e®ort is devoted to improving the e±ciency of signal detection,[22] spectral contrast of the spectrometer[23,24,25] and removing background components.[26,27,28,29] Here, we present an analysis method of the Brillouin spectrum based on the spectral autocorrelation function of the acquired signal We will show both analytically and experimentally that working in the autocorrelation space is advantageous compared to current protocols in terms of localization precision

Principle

Theory

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Experimental Data

Findings

Discussion