• Future demands in high capacity telecommunication (40Gb/s and beyond) require components with small dimensions (mm) and low voltage operation(5V).
• Several functional oxides, i.e., BaTiO₃, PZT/PLZT and others show very large electro-optical coefficients
• The large electro-optical coefficients allows for a reduction in component size and operational voltage, simplifying high-bandwidth operation.

Example: Mach Zehnder wave-guide

The image depicts model data of a Mach-Zehnder modulator with the two branches being in-phase (left image below). This ensures constructive interference of the signal from the two branches and the optical output is at maximum. When an appropriate voltage is applied to electrodes across one arm in the interferometer, the phase of the optical signal in that arm will be shifted and the device output will approach zero. The right image is an optical micrograph a y-junction at one end of a Mach-Zehnder interferometer.

Cross section of one of the arms of the Mach Zehnder wave-guide. Control of the refractive index allows the use of PZT/PLZT core cladding structure to ensure vertical optical confinement (left image). On the right: SEM of a stack with low-index cladding layer (PLZT) and high-index core (PZT) on Si substrate with Pt-electrode. The PZT layer exhibits a pronounced columnar structure.

For visualization, red laser light (630nm) is fed into the waveguide structure through a tapered optical fibre. The waveguides are designed for operation at standard telecommunication wavelengths (1500nm).

Contact: Camilla Haavik