The nonlinear interaction of TE and TM optical modes with a microwave by means of optical rectification and the electro-optic effect in a traveling-wave structure is investigated. The phase velocity mismatch between the optical waves leads to effects that are essentially different from those in the single-polarization case. Whereas, for a velocity-matched structure, alternating upconversion and downconversion occur, a slight difference between optical group velocity and microwave phase velocity gives rise to a sinusoidal terahertz signal with a number of cycles that depends on beat length, length of the structure, and velocity mismatch. A structure for on-chip generation of tunable narrow-bandwidth terahertz signals is suggested. Cascading caused by optical rectification and the electro-optic effect can lead to an effective change of beat length and self-induced mode conversion at high optical powers.
© 2002 Optical Society of America
Karsten Bubke, David C. Hutchings, and Ulf Peschel, "Mixed-polarization optical rectification in semiconductor waveguides," J. Opt. Soc. Am. B 19, 881-889 (2002)