Non-collinearly phase-matched frequency mixing

A method for non-collinearly phase-matched frequency mixing of laser beams, comprising steps of:

• generating first and second input laser beams;
• and
• directing the first and second input laser beams into a first nonlinear crystal such that (i) wave vectors of the first and second input laser beams are non-collinear and intersect in the first nonlinear crystal, and (ii) the first and second wave vectors cooperate with the orientation of the first nonlinear crystal to promote non-collinearly phase-matched frequency mixing of the first and second input laser beams resulting in generation of an output laser beam, the output laser beam is subject to walk-off in a walk-off plane in the first nonlinear crystal;
• wherein:
• the first input laser beam is more powerful than the second input laser beam,
• the transverse size of the second input laser beam, in the walk-off plane, exceeds a corresponding transverse size of the first input laser beam, and
• in the first nonlinear crystal, an angle between a Poynting vector of the first input laser beam and a Poynting vector of the output laser beam is smaller than an angle between a Poynting vector of the second input laser beam and the Poynting vector of the output laser beam.