Abstract

Intense light can cause germanium-doped glass to act like a doubling crystal and convert light at frequency co into light at frequency 2ω. Recent theories of this effect invoke the presence of a dc electric field inside the glass. We present a method for mapping out this dc electric field inside a glass fiber preform. We first prepare the preform by injecting beams of both 1064 nm and 532 nm into the preform core. Both injected beams have the same polarization. We then map the resulting dc electric field by using the polarization properties of the induced nonlinearity, which we assume arise from the internal dc electric field and the non-resonant χ⁽³⁾ of fused silica. By selecting vertically polarized reading light and a vertically oriented analyzer we probe only the vertical component of the induced field, and similarly for the horizontal component. We also measure the relative phase between these two components. We confirm the result of Mizrahi et al.¹ that the polarization properties of the second-harmonic process are completely predicted by assuming a dc electric field and the χ⁽³⁾ of the isotropic preform. This mapped field shows that charge is transported along the direction of polarization of the beams that prepared the glass preform.

© 1992 Optical Society of America