Birefringent and nonlinear optical assessment of single crystal lithium niobate fibres

a-axis fibres of lithium niobate produced by laser heated miniature pedestal growth can possess transverse and longitudinal birefringence variations due to faceted growth. When used for second harmonic generation, these characteristics cause conversion efficiencies to be two to three orders of magnitude smaller than predicted and the phasematchable lengths and apertures to be short. Second harmonic generation and associated birefringence mapping are shown to be sensitive indicators of their uniformity