Comparison of pulsed-excitation and phase-modulation methods for estimating fluorescence lifetime values using a convolved-autoregressive model and a high-gain photomultiplier tube

A comparative study between pulsed excitation (PE) and phase modulation (PM) methods has been carried out numerically and experimentally to estimate fluorescence lifetime values in the combined use of the following two measurement techniques: (i) To enhance the sensitivity in light detection, we have connected a load resistor with a large value at the output of a photomultiplier tube (PMT), which also brings about improvement in the signal-to-noise ratio (SNR) in measurements. (ii) The application of a convolved-autoregressive (C-AR) model to time-series data obtained from such a high-gain PMT enabled us to precisely estimate the fluorescence lifetime values in a nanosecond region. Although dependent on various measurement parameters, we have found that the PM method has potential in the field of biology or biochemistry for screening fluorescent samples.