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Direct third harmonic generation due to quadratic cascaded processes in periodically poled crystals |
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| Authors: | S.K. Das N. Sinha P.K. Datta S.M. Saltiel |
| Affiliation: | a Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302, India b Department of Electrical Engineering, Indian Institute of Technology, Kharagpur 721 302, India c Faculty of Physics, University of Sofia, 5 J. Bourchier Boulevard, BG-1164 Sofia, Bulgaria d INFM, Università di Pavia, Via Bassi 6, I-27100 Pavia, Italy |
| Abstract: | We report the first, according to our knowledge, experiment for direct third harmonic (TH) generation in periodically poled quadratic crystals. TH radiation of a diode array pumped and acousto-optically Q-switched Nd:YVO4 laser is generated in a 25 mm long periodically poled lithium niobate (PPLN) crystal of period 7.0 μm. A theoretical model is developed that explains the experimental results. It predicts that the efficient phase-matched direct TH generation in periodically poled structures with duty factor 0.5 requires even order quasi-phase matching. In contrast to the similar experiments in bulk birefringence crystals, where direct phase matched TH signal is the sum of the contribution of both intrinsic and cascaded cubic nonlinearities, in periodically poled quadratic crystals only cascaded cubic nonlinearity contributes to the direct phase-matched TH signal. |
| Keywords: | 42.79Nv 42.65Ky 42.55Xi |
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