The linear electro-optic (Pockels) effect of wurtzite gallium nitride (GaN) films and six-period GaN/AlxGa1-xN
superlattices with different quantum structures were demonstrated by a polarization-maintaining fiber-optical Mach-Zehnder interferometer system with an incident light wavelength of 1.55μm. The samples were prepared on (0001)
sapphire substrate by low-temperature metalorganic chemical vapor deposition (MOCVD). The measured coefficients of
the GaN/AlxGa1-xN superlattices are much larger than those of bulk material. Taking advantage of the strong field
localization due to resonances, GaN/AlxGa1-xN SL can be proposed to engineer the nonlinear responses.
Novel compact design for 4-channel SOI-based reconfigurable optical add/drop multiplexer using microring resonators
is presented and analyzed. Microring resonators have two important attributes as a key new technology
for future optical communications, namely functionality and compactness. Functionality refers to the fact that
a wide range of desirable filter characteristics can be synthesized by coupling multiple rings. Compactness refers
the fact that ring resonators with radii about 30μm can lead to large scale integration of devices with densities on
the order of 104 - 105 devices per square centimeter. A 4-channel reconfigurable optical add/drop multiplexer
comprises a grid-like array of ridge waveguides which perpendicularly cross through each other. SOI-based resonators
consisted of multiple rings at each of the cross-grid nodes serve as the wavelength selective switch, and
they can switch an optical signal between two ports by means of tuning refractive index of one of the rings. The
thermo-optic coeffcient of silicon is 1.86×10-4/K. Thus a temperature rise of 27K will increase the refractive
index by 5×10-3, which is enough to cause the switching of our designed microring resonators. The thermo-optic
effect is used to suppress the resonator power transfer, rather than to promote loss. Thus, the input signal only
suffers small attenuation and simultaneously low crosstalk can be achieved by using multiple rings.
Our configurable optical add/drop multiplexers (OADM) are based on
thermally tunable silicon-on-insulator(SOI) Bragg gratings. We
have simulated the whole device and get ideal performance. We also
tried experiments to explore the process of grating waveguide and
got useful results.