A disadvantage of mechanically scanned sonogram measurements is the slow speed of acquisition and the inability to make a single-shot measurement of the pulse. Our single-shot method resolves this problem by generating a cross-correlation using Type II (opposite input polarisations) sum-frequency mixing in the crystal KDP. The unique phase-matching properties of KDP mean than one polarisation sees a narrow acceptance bandwidth (a few nm) while the opposite polarisation experiences a very large (~100 nm) bandwidth.

The orientation of the KDP crystal is shown above.

The single shot sonogram (figure above) works by resolving time along one direction and frequency (wavelength) along the opposite direction. The sonogram cross-correlation is spatially resolved within the KDP crystal (see Top View) and is imaged onto a CCD detector using a pair of cylindrical / spherical lenses. The angular variation of the phasematching within the crystal (see Side View) so that different wavelengths emerge at different angles and are then imaged at different heights on the CCD detector.

The figure below shows examples of sonograms measured using the single-shot apparatus for positive, near-zero and negative linear chirp.