Figure 3

Two-dimensional images of an onion sample.

Panel (a) was taken with the TL pulse with no unbalanced dispersion, (b) TL pulse with 3 mm of BK7 in the sample arm for unbalanced dispersion (d) BARC pulse, no dispersion and (e) BARC pulse with unbalanced dispersion. The colour-bar represents the natural logarithm of the number of counts per delay-arm motor step recorded by the photomultiplier. The internal cellular structure of the onion is visible deep into the sample in all four images and comparing the images we see that no artifacts are introduced by using BARC pulses. A single axial scan at the transverse position indicated by the red vertical line in each image are plotted on a linear scale beside each corresponding image; the labels represent the widths of each peak FWHM in micrometres. The addition of dispersion significantly broadens the TL-pulse peaks while in contrast the BARC-pulse peaks are dispersion cancelled. Peak widths over each entire image are plotted as histograms shown in panels (c) and (f), for the TL and BARC pulses respectively; the black bars are used for no unbalanced dispersion and the red for unbalanced dispersion. The peak widths for the TL pulses broadened by 61% with the addition of dispersion, while those from the BARC pulses broadened only by 4%. Dispersion cancellation is thus achieved over the entire image.