Third-order nonlinear optics in KTP ridge waveguides

Ridges waveguides carved in bulk nonlinear crystals such as LiNbO 3 [1] or KTiOPO 4 (KTP) [2] are a good alternative to reach a strong confinement of electromagnetic waves with large second-order or third-order non-linearity. We report here on our most recent experiments where we show the possibility to shape the birefringence phase-matching (BPM) conditions for direct Third-Harmonic Generation (THG: ω + ω + ω → 3ω) in micrometric KTP ridge waveguides by acting on their transverse dimensions. This study is the preliminary step for designing quantum optical experiments based on Triple Photons Generation (TPG: 3ω → ω + ω + ω) that is the reverse process of THG, thus exhibiting the same BPM conditions.