1060 nm interferometric near-infrared spectroscopy

Recently, interferometric near-infrared spectroscopy (iNIRS) has emerged to measure diffuse light field fluctuations with time-of-flight (TOF) resolution. Yet, current iNIRS implementations suffer from low signal-to-noise ratio (SNR). Longer wavelengths, with lower photon energy, lower reduced scattering in biological tissues, and higher permissible exposures, have the potential to increase SNR. Here, we investigate iNIRS at 1060 nm. Across various forehead locations, we find that the autocorrelation SNR is improved 3.7-9.3 times compared to 855 nm and 6.0-33.5 times compared to 773 nm at TOFs of 800-1000 ps. Physical system parameters account for much of this improvement, but the tissue response may also play a role. We conclude that wavelengths near 1060 nm can potentially improve iNIRS measurements of TOF-resolved speckle fluctuations.