Singly-resonant parametric oscillation in periodically poled KTiOPO/sub 4/ pumped by Bessel beam

Summary form only given. Conical light beams can be used to produce sharply peaked intensity distribution in the focus, appropriately defined by the Bessel function J/sub 0/ (r) modulated by a Gaussian envelope, hence Bessel-Gauss beams. The extent of the region over which this distribution is sustained, the so called "diffraction-free" zone can be larger than the Rayleigh length of the Gaussian beam with the equivalent beam waist size. This property has been exploited for more efficient harmonic generation in gases. The Bessel-Gauss beams have the specific phase matching properties where the highest coupling efficiency is obtained along the axial direction of the conical pump beam. We recently exploited this property to efficiently generate a Gaussian axial second harmonic beam from a conical fundamental beam in periodically poled KTiOPO/sub 4/ (PPKTP).