Novel photonic crystal designs in Er:Ti:LiNbO3 waveguides

The combination of the amplifying properties of erbium with the excellent electro-optical, acousto-optical and non-linear properties of the waveguide substrate LiNbO₃ allows the development of a whole class of new waveguide devices of higher functionality. The analysis of Er-doped diffused channel waveguides is, hence, required for design of amplifying integrated optical circuits in order to optimize the performance of these gain devices. Photonic crystals (PhCs) have given birth to a number of realizations. Photonic integrated circuits around new integrated lasers are challenging directions of research for miniaturization and new functions in optical telecommunications. Control of spontaneous emission is one of the main applications of active PhCs. In this paper, we will focus on triangular-lattice photonic- crystal waveguides on Ti:Er:LiNbO₃ substrate at the 1.5-mum wavelength by optical pumping. The lattice period and the airhole diameter of the proposed structure are varied over a large scale, thereby allowing a detailed exploration of the optical gain in the cases of micrometer-width waveguides. A novel laterally over-modulated (LOM) waveguide structure is presented. One advantage of such a structure as compared to classical distributed feedback (DFB) structures stems from the fact that the device fabrication does not require any regrowth step, which is a critical fabrication step. Another advantage of PhCs-based integrated optics around laser sources results from the fact they operate in a single polarization (TM) mode. This relaxes the constraints on the behavior of the optical chain in the (TE) polarization, in a sharp contrast with the requirements imposed on a receiving system. A calculation from a two dimensional-plane wave and FDTD models shows a favorite transmission at 1.5-mum combined to favorite field distributions and band diagram in the GammaK direction.