The two-photon absorption spectrum and cross-section (δ) for ruby (Cr3+:sapphire) have been measured over the 0.8–1.2 μm wavelength range at 25°C. Absolute values of δ
were obtained by comparing the fluorescence yield for two-photon
excitation with that for single-photon excitation of the same ionic
transition under identical illumination conditions. The maximum values
of δ are 4.6×10−3 GM for o-polarisation and 5.9×10−3 GM for e-polarisation at 840 nm. The relevance of these measurements to distributed optical fibre sensing is briefly discussed.
- single crystal fiber