We describe an instrument for the time-resolved spectroscopy of turbid media that is based on supercontinuum generation in a photonic crystal fiber. The light injected into the sample consists of subpicosecond pulses that cover 550–1000 nm at 85 MHz at an average power of as much as 40 mW. A spectrometer coupled to a multianode photomultiplier tube is used to detect the light simultaneously in 16 wavelength channels, with a resolution of 5–20 nm/channel, depending on the grating. Time-correlated single-photon counting is used to produce time-dispersion curves, which one fits to the diffusion equation to determine absorption and reduced scattering coefficients. We tested the instrument by measuring the time-resolved diffuse reflectance of epoxy phantoms and by performing <i>in vivo</i> measurements on volunteers. The results were similar to those obtained with previous discrete wavelength systems, whereas the full spectrum (610–810 nm) acquisition time was as short as 1 s owing to the parallel acquisition.
© 2004 Optical Society of America
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(170.6510) Medical optics and biotechnology : Spectroscopy, tissue diagnostics
(170.7050) Medical optics and biotechnology : Turbid media
(300.6500) Spectroscopy : Spectroscopy, time-resolved
Andrea Bassi, Johannes Swartling, Cosimo D'Andrea, Antonio Pifferi, Alessandro Torricelli, and Rinaldo Cubeddu, "Time-resolved spectrophotometer for turbid media based on supercontinuum generation in a photonic crystal fiber," Opt. Lett. 29, 2405-2407 (2004)