  Following various works on second harmonic process using periodically poled
Lithium Niobate crystals (PPLN), we report on the performances comparison
between commercial bulk and waveguide crystals at 1029 nm. We use a continuous
wave (CW) amplified Yb doped single fibre laser delivering up to 500mW in
single mode regime. In case of bulk crystal we generate 4 mW using 400 mW IR
power. The use of waveguide crystal leads to an increase of the harmonic power
up to 33mW with input IR power limited to 200mW. Nevertheless, this impressive
efficiency was affected by the long term degradation of the non-linear
waveguide crystal.
