Decoupling phase-matching bandwidth and interaction geometry using non-collinear quasi-phase-matching gratings.

In optical parametric amplification (OPA) of broadband pulses, a non-collinear angle between the interacting waves is typically introduced in order to achieve broadband phase-matching. Consequently, bandwidth and beam geometry are closely linked. This coupling restricts the geometrical layout of an OPA system. Here, we demonstrate a quasi-phase-matching (QPM) geometry for broadband OPA in which a transverse component is introduced to the QPM grating to impose an additional momentum on the generated wave. This momentum shift detunes the wavelength where the signal and the idler are group-velocity matched, thereby allowing for broadband phase-matching without having to add a non-collinear angle between the interacting waves. We present two experimental configurations making use of this principle, and propose a third configuration with the potential to further simplify ultra-broadband OPA system architectures.