Tunable arrayed waveguide Demultiplexer on X- cut LiNbO3

The design of demultiplexers based on array waveguides is well known [1-5]. A new design based on the concept of variable waveguide depth was recently reported [6]. Since, the fabrication of channel waveguides on glass, silica or lithium niobate is mostly controlled by the lithography pattern and the subsequent fabrication process, it is difficult to implement the variable depth concept on these materials. We proposed the concept of variable waveguide width to design array waveguide demultiplexer on X-cut lithium niobate [23]. This work was further extended to design a 4 channel 100 GHz tunable demultiplexer on lithium niobate. The central wavelength of the device can be electro-optically controlled. This work is reported here in the paper. The device simulation is performed at 1550nm central wavelength for a TE polarized light. A single mode annealed proton exchanged wave-guide, having a width of 1.5μm and depth 1μm is chosen for the simulation. The simulation is carried out using the WDM-PHASAR and Optiwave 5.0 software, based on the beam propagation method. The number of array waveguides in the array section is thrice that of the input or output waveguides. Where as in the conventional arrayed waveguide grating (AWG) the number of array waveguides is >4 times that of the input or output waveguides. The array waveguide region architecture differs from the conventional designs. The typical waveguide to waveguide separation in AWG region varies from 3 to 8 microns. The S-bends are used to avoid evanescent coupling between the adjacent waveguides, which otherwise leads to the phase error and intra-channel cross talk. The free spectral range for TE polarized light is in 5THzThe neighboring channel crosstalk is less than -100db and the device crosstalk varies from -50 to -60db. The nonuniformity is less than 0.1 dB. The simulated loss is less than 0.8db for all the channels.