Spatial Coherence Measurement of Soft X-Ray Radiation Produced by High Order Harmonic Generation.

We have executed a series of Young’s two-slit experiments to measure the spatial coherence of soft x rays produced by high order harmonic generation in helium within the 270 to 480 A wavelength range. We find that the harmonics exhibit good fringe visibility and high spatial coherence, though the coherence is somewhat degraded at high intensity because of the production of free electrons through optical field ionization during the harmonic generation. [S0031-9007(96)01799-1]