Abstract

Since the first report¹ of efficient second-harmonic generation (SHG) in glass optical fibers four years ago, a number of models have been put forward to explain the effect. These can be roughly divided into two categories. In some models^2,3,4 it is proposed that an internal d.c. electric field is set up which, acting on the χ⁽³⁾ of the glass, serves as an effective χ⁽²⁾. In other models^5,6,7 it is proposed that the macroscopic χ⁽²⁾ originates from an orienting of dipoles ("defects") in the glass. We have examined the polarization properties of the second-harmonic light generated by a single mode germania doped fiber. From the observed behavior we deduce that the effective χ⁽²⁾ of the fiber behaves as a χ⁽³⁾ of a nondispersive isotropic material (glass) acted on by a transverse d.c. electric field; in other words, we are likely dealing with an electric-field induced second-harmonic generation (EFISH) phenomenon.

© 1990 Optical Society of America