A wavelength conversion device employs an axicon lens to form Bessel beams of signal light and pump light, which are directed into an anisotropic nonlinear optical crystal. The signal light and pump light are both polarized parallel to the uniquely determined Z-axis of the anisotropic nonlinear optical crystal, the Z-axis being oriented perpendicular to the beam axis. The axicon lens is configured to refract the signal light and pump light at angles such that a phase matching condition is satisfied in the anisotropic nonlinear optical crystal, and converted light, also polarized parallel to the Z-axis and having a new wavelength, is generated.