Description
We have observed anomalous conical emission from the first resonant transition of calcium (λca=422.67nm) using two types of laser beam, Gaussian and zeroth-order Bessel beams. We used the third harmonic of a Nd:YAG laser to pump a homemade tunable dye laser to excite the transition, and a 1° axicon to produce the Bessel beams. The conical emission featured different half-angles for the same wavelength as a function of the excitation beam. The results of our experiments support conical emission models based upon four-wave mixing, and we believe this is due to the fact we have modified the phase-matching condition with the zeroth-order Bessel beam wave vector.
