The excitation source was a broadband super-continuum (SC) fiber laser (Koheras SuperK Power, NKT Photonics, Birkerod, Denmark) fitted with a beam splitter unit (SpectraK Split, NKT Photonics) and a 640-nm bandpass filter (10-nm FWHM, Chroma Technologies, Bellows Falls, Vermont). We note that we used the SC only as a broadband light source and did not use the pulsed properties of the laser output. The laser was coupled into the excitation fiber using an SMA-coupled achromatic lens package (F230 SMA-B; Thorlabs Inc., Newton, New Jersey) and the power at the sample was 9 mW. The eight collection fibers were divided into two bundles of four fibers (alternating around the probe so that the detected signal was approximately symmetrical), which were also terminated on SMA-coupled lens packages (F260 SMA-B; Thorlabs) to collimate the output light. One output arm was passed through a 690-nm emission filter (50-nm FWHM, Chroma) and focused onto a photomultiplier tube (PMT; H6780-20, Hamamatsu Photonics, Bridgewater, New Jersey) with a 25-mm focal length lens (Edmund Optics, Barrington, New Jersey). The second output arm was not used for these experiments but could be used in the future, for example, for multispectral experiments. The output of the PMT was amplified with a current preamplifier (SR570, Stanford Research Systems, Sunnyvale, California) configured with 100-Hz low-pass filter, and acquired with a data acquisition card (DAQ; NI-USB-6251, National Instrument, Austin, Texas). The DAQ was controlled using a custom script written in MATLAB (The Mathworks Inc., Natick, Massachusetts).