Abstract

For second-harmonic generation (SHG), the phase difference ΔΦ between the fundamental and the harmonic is determined by the phase of the underlying complex-value second-order susceptibility χ⁽²⁾ Hence, by controlling the phase of χ⁽²⁾, one should be able to control ΔΦ. This has been demonstrated by using nematic-liquid-crystal (NLC) cells with an externally applied dc field of alternating polarity. Their effective susceptibility ${\chi }_{\text{eff}}^{\left(2\right)}$ consists of an electrically controllable bulk contribution ${\chi }_{\text{lc}}^{\left(2\right)}$ proportional to the applied voltage U and a voltage- independent background ${\chi }_{\text{const}}^{\left(2\right)}$. This background contribution is due to the adjacent cell Windows, which were IOT-coated and carried a thin rubbed polyimide layer for molecular alignment. We demonstrated the electrically controllable phase using the second-harmonic-interference technique, originally introduced by Bloembergen and Pershan.¹ Two types of NLC cells were studied: pure NLC cells and an NLC cell with an embedded guest of high optical nonlinearity.

© 1995 Optical Society of America