1. A system that characterizes a light beam, comprises: a nonlinear crystal receiving a first fundamental beam and a second fundamental beam and generating a first second harmonic beam, a second second harmonic beam and a sum frequency beam, the first fundamental beam and the second fundamental beam having a fundamental optical carrier frequency v 0, the first fundamental beam and the second fundamental beam intersecting the nonlinear crystal at an angle &agr;, the first fundamental beam optically delayed from the second fundamental beam, the optical nonlinearity of the crystal enabling a generation of the first second harmonic beam, second harmonic beam, and the sum frequency beam, a thickness of the nonlinear crystal ensures a phase matching for the first second harmonic beam, the second second harmonic beam and the sum frequency beam; a lens receiving the first second harmonic beam, the second second harmonic beam, and the sum frequency beam and refracting the first second harmonic beam, the second second harmonic beam, and the sum frequency beam; a mask, the mask optionally selectively blocking at least one of the first second harmonic beam and the second second harmonic beam; and an image detector receiving the sum frequency and at least one of the first second harmonic beam and the second second harmonic beam and registering an asymmetric autocorrelation function, the asymmetric autocorrelation function determining a sign of a phase modulation of at least one of the first fundmental beam and the second fundamental beam.