The following is an abstract for the selected article. A PDF download of the full text of this article is available here. Members may download full texts at no charge. Non-members may be charged a small fee for certain articles.
Cross-Term Selective, Two-Pulse Correlation Measurements by Phase-Shifted Parallel Modulation for Analysis of a Multi-Photon Process
Volume 66, Number 12 (Dec. 2012) Page 1475-1479
KOICHI FURUTA, MASANORI FUYUKI, and AKIHIDE WADA*
We propose a new modulation technique for phase-sensitive detection to extract a cross-term signal appearing in multi-pulse experiments and demonstrate the selective detection of cross-term signal on two-pulse correlation measurements. This modulation technique can be widely applied to the selective detection in multi-beam laser experiments such as two-pulse correlation, auto-correlation, and double-resonance experiments, because the selectivity can be realized by using a conventional single-frequency mechanical chopper and 2f phase-sensitive detection. The effectiveness of the proposed technique was confirmed by two-pulse correlation measurements of two-photon-excited fluorescence from rhodamine 6G. In addition to the selective observation of a correlation peak, the technique succeeded in observing a weak correlation background. By combining asymmetric, two-pulse correlation measurements with the proposed technique, it was clarified that the background was produced by a three-photon process and assigned to fluorescence depletion caused by an up-conversion process. The results indicate that the cross-term selective, two-pulse correlation method that is based on the phase-shifted parallel modulation technique is powerful tool to find and analyze a high-order optical event buried in a low-order optical event.
Index Headings: Two-pulse correlation; Multi-photon process; Cross-term selective technique; Phase-sensitive detection; Rhodamine 6G; Two-photon-excited fluorescence; Fluorescence depletion.