Electrically poled KT¥provides second-harmonic generation in waveguides

Electrically poled KT¥provides second-harmonic generation in waveguides

Researchers at the IBM Almaden Research Center (San Jose, CA) have fabricated periodically poled potassium titanyl phosphate (KTP) waveguides using electric-field poling. Frequency doubling the output of a Ti:sapphire laser with the waveguides provided 12 mW of blue (431 nm) TEM00 output from 146 mW of near-IR pum¥light.

The large nonlinear coefficient and high damage threshold of KT¥has previously led to its use for waveguide frequency doubling. At shorter wavelengths, quasi-phasematching must be used and is accomplished by periodic inversion of the spontaneous polarization of the ferroelectric domains of the material. Production of such waveguides with the required properties has been accomplished using an ion-exchange technique, but this method means the domain-inverted region may not be as dee¥as the waveguide and that domain-inversion reliability and reproducibility is questionable.

According to IBM researchers, electric-field poling produces a quasi-phasematched waveguide in KT¥with dee¥domains that permit independent optimization of the linear and nonlinear properties. Further work is under way to increase the interaction length of the waveguides, improve poling uniformity, and optimize linear-waveguide properties.