The design and fabrication of an integrated waveguide polarizer in z-cut LiNbO3 crystals are reported. Single-polarization guiding is achieved by careful selection of Ti diffusion parameters exploiting the transverse electric/transverse magnetic (TE/TM) refractive index anisotropy. Fabricated Ti:LiNbO3 waveguide polarizers of 1.5 cm length exhibit less than 0.2-dB/cm propagation loss at TM and 33-dB extinction ratio as measured at 1.55-µm wavelength.
We present the design of a tunable wavelength filter based on an active arrayed waveguide grating (AWG). We show a novel layout and simulated performance of a tandem filter configuration that covers 43 nm in C band with 0.2-nm (25-GHz) channel spacing at –35-dB crosstalk level. Design of the device is based on Fourier-Fresnel formalism with special emphasis on tuning mechanisms. The Gerchberg-Saxton phase retrieval method is used to estimate phase errors and generate phase patterns required for device tuning. A polarization insensitive filter is presented with its main parameters and simulation results. The technological considerations of achieving nanoseconds-scale tunability by exploiting the electro-optical effect in LiNbO3 crystals are discussed in detail. Such a filter may find various applications in packet-switched coarse and dense multiwavelength dynamic networks.
In this work we discuss a method of smooth waveguide fabrication by wet etching, using a novel mixture of organic and inorganic acids. We fabricated 4.5μm-deep large single mode waveguides with walls and edges roughness comparable with the roughness of non-etched regions. Surface and wall roughness as well as etching rates and propagation losses are presented and compared to characteristics achieved by traditional wet etching recipes. The method was developed as part of the effort to implement fast and widely tunable AWG-based wavelength filter with channel spacing suitable for dense WDM networks.