Measurement of the phase of second-harmonic generation in SK5 glass

Focusing an intense laser beam and its second harmonic into a SK5 glass slab transforms the glass into a frequency doubler. We present a new method to measure the optical phase between the second-harmonic beam that transformed the glass and the second-harmonic beam subsequently generated by the glass. We find this phase shift to be Deltatheta= -90 degrees +/- 7 degrees . A spatial map of this phase confirms that the internal dc electric field locked inside the glass resembles a dipole electric field.