  We demonstrate a novel, composite laser written 3D waveguide, fabricated in
boro-aluminosilicate glass, with a refractive index contrast of 1.12 x 10^-2.
The waveguide is fabricated using a multi-pass approach which leverages the
respective refractive index modification mechanisms of both the thermal and
athermal inscription regimes. We present the study and optimisation of
inscription parameters for maximising positive refractive index change and
ultimately demonstrate a dramatic advancement on the state of the art of bend
losses in laser-written waveguides. The 1.0 dB cm^-1 bend loss cut-off radius
is reduced from 10 mm to 4 mm, at a propagation wavelength of 1550 nm.
