Increasing time resolution of picosecond absorption spectrometer by selection of length of laser light pulses

Picosecond adsorption spectroscopy requires measurement of changes in the absorption of light in the specimen studied, induced by an exciting light pulse. With very rapid relaxation, the signal recorded depends not only on the amplitude, but also on the time profile of the pulses, so that fluctuations in pulse length contribute to measurement error. A method is suggested for monitoring the relative change in picosecond pulse length and selecting pulses within a predetermined length range based on generation of a second harmonic. Length selection of pulses in a spectrometer increases the accuracy of recording spectrometric curves and improves the time resolution of the method. The statistical parameters of picosecond spectrometer light pulses were measured, demonstrating the possibility of decreasing measurement error by selection of pulses by length.