T. J. Spencer (optical physicist)

T. J. Spencer is a coauthor of the Central Laser Facility's1999 report on a single-shot instrument for third-order intensity autocorrelation and optical pulse temporal contrast measurements.^[ref]

An original calculation illustrates a pulse-characterization issue relevant to that work. Let a Gaussian pulse have intensityCompleting the square in its third-order intensity autocorrelation givesThe pulse's intensity full width at half maximum is $2\sqrt{2\ln 2}\sigma$, while the correlation width is $2\sqrt{3\ln 2}\sigma$. Their ratio is thereforeA measured correlation width cannot simply be reported as the original pulse width. The conversion depends on the assumed pulse shape and the correlation being measured. This Gaussian example explains that distinction; it is not a reconstruction of Spencer's individual experimental tasks or a fit to the1999 data.