Figure 1

Schematic diagram of the experimental arrangement with relative separations exaggerated for clarity.

The fundamental and harmonic beams are shown in red and purple respectively. The inset represents the evolution of the harmonic beam diameter (purple contour) and wavefront (green solid lines) with propagation distance. The notation employed is defined in the sketch and is as follows: subscript ‘G’ for generation plane; subscript ‘E’ for effective source plane; subscript ‘M’ for measurement plane.