Frequency conversion of laser radiation

A method comprising:

• receiving, in a first nonlinear crystal, a first laser beam having a first wavelength λ1;
• generating, in the first nonlinear crystal and by frequency doubling of the first laser beam, a second laser beam having a second wavelength λ2, wherein the second laser beam propagates collinearly with respect to the first laser beam;
• directing the first laser beam and the second laser beam toward one or more lenses, wherein the one or more lenses spatially separate the first laser beam and the second laser beam;
• receiving, in a second nonlinear crystal, the spatially separated first laser beam and the second laser beam from the one or more lenses;
• and
• generating, in the second nonlinear crystal and by frequency mixing of the first laser beam and the second laser beam, a third laser beam having a third wavelength λ3,
• wherein the first laser beam and the second laser beam propagate through the one or more lenses at an offset with respect to an optical axis of the one or more lenses, or at an angle with respect to the optical axis of the one or more lenses, or at an offset and at a angle with respect to the optical axis of the one or more lenses.

A system comprising:

• a first nonlinear crystal, arranged to receive a first incident laser beam having a first wavelength λ1, and operable to generate, by frequency doubling of the first laser beam, a second laser beam having a second wavelength λ2, wherein the second laser beam propagates collinearly with the first laser beam;
• a second nonlinear crystal, arranged to receive the first laser beam and the second laser beam, and operable to generate, by frequency mixing of the first laser beam and the second laser beam, a third laser beam having a third wavelength λ3;
• one or more lenses arranged between the first nonlinear crystal and the second nonlinear crystal, wherein the one or more lenses are operable to spatially separate the first laser beam and the second laser beam from one another prior to the first laser beam and the second laser beam being incident on the second nonlinear crystal;
• and
• one or more movement devices coupled to the one or more lenses, respectively, wherein the one or more movement devices are operable to move a corresponding lens perpendicularly to an optical axis.