Fabrication and optical characterisation of planar silica lens pair

The fabrication and experimental results on the performance of a planar silica lens pair that facilitates low-loss optical beam propagation in free space between opposing planar silica waveguides/singlemode fibres are presented. Each lens uses the parabolic graded refractive index vertically and the convex curvature horizontally to focus the optical beam in free space. The lens pair, designed for 200 m of free space propagation distance with ideal zero loss, is fabricated and measured for net loss of 1.6 dB which is 12.4 dB less than the coupling loss without a lens pair at 633 nm wavelength.