Interferometric speckle visibility spectroscopy (iSVS) for measuring decorrelation time and dynamics of moving samples with enhanced signal-to-noise ratio and relaxed reference requirements

TL;DR

This paper introduces interferometric speckle visibility spectroscopy (iSVS), a technique that enhances signal-to-noise ratio and relaxes reference requirements for measuring dynamics in scattering media, especially useful in photon-limited biological applications.

Contribution

The paper presents a theoretical and experimental analysis showing iSVS's superior SNR performance and relaxed reference constraints compared to traditional diffusing wave spectroscopy methods.

Findings

iSVS provides better SNR by overcoming camera noise.

iSVS has relaxed constraints on reference beam properties.

Experimental validation confirms theoretical advantages.

Abstract

Diffusing wave spectroscopy (DWS) is a group of techniques used to measure the dynamics of a scattering medium in a non-invasive manner. DWS methods rely on detecting the speckle light field from the moving scattering media and measuring the speckle decorrelation time to quantify the scattering mediums dynamics. For DWS, the signal-to-noise (SNR) is determined by the ratio between measured decorrelation time to the standard error of the measurement. This SNR is often low in certain applications because of high noise variances and low signal intensity, especially in biological applications with restricted exposure and emission levels. To address this photon-limited signal-to-noise ratio problem, we investigated, theoretically and experimentally, the SNR of an interferometric speckle visibility spectroscopy (iSVS) compared to more traditional DWS methods. We found that iSVS can provide excellent SNR performance through its ability to overcome camera noise. We also proved iSVS system has more relaxed constraints on the reference beam properties than most other interferometric systems. For an iSVS to function properly, we simply require the reference beam to exhibit local temporal stability, while incident angle, reference phase, and intensity uniformity do not need to be constrained. This flexibility can potentially enable more unconventional iSVS implementation schemes.