LiNbO<sub>3</sub> single-crystal fibers with diameters of 63 and 230 μm were grown, and the second-harmonic-generation (SHG) process was studied with femtosecond laser pulses perpendicularly focused to the fiber. SHG occurred without collinear phase matching, leading to wavelength-independent overall conversion efficiency, unlike in a bulk crystal. The scattering pattern of the second harmonic exhibited an intense forward peak and an almost-uniform, less-intense distribution around the fiber, owing to trapping in high-<i>Q</i> whispering modes. Implementation of a second-order autocorrelator with the 63-μm fiber demonstrates its application potential.
© 1999 Optical Society of America
(190.2620) Nonlinear optics : Harmonic generation and mixing
(290.0290) Scattering : Scattering
(320.2250) Ultrafast optics : Femtosecond phenomena
(320.7110) Ultrafast optics : Ultrafast nonlinear optics
J. Yu, K. Giulietti, F. Sourgen, A. Ross, J. P. Wolf, M. Ferriol, G. Foulon, C. Goutaudier, M. T. Cohen-Adad, and G. Boulon, "Second-harmonic generation in a microradius LiNbO3 cylinder with a quasi-elliptical cross section," Opt. Lett. 24, 394-396 (1999)