Improved design for SOI based evanescently coupled multilayer spot-size converter

We report an improved version of a spot-size converter (SSC) consisting of a silicon nanowire evanescently coupled to a phase-matched Poly-Si multilayer structure. With wider transversal dimensions the multilayer structure expands the mode significantly thus increasing the coupling efficiency with the conventional single-mode fiber. Detailed optimization process of a 17-layer based SSC is discussed and its coupling efficiency with a high-NA fiber of radius 2 μm is obtained as 98% providing only 0.087 dB loss. Vertical alignment tolerance between the optimized SSC and a high-NA fiber of radius 2 μm is also shown. This novel design does not consist of a taper and can be fabricated by using CMOS compatible process. It has a short device length and more relaxed alignment tolerances with the fiber. Full-vectorial and computationally efficient finite element method and the least squares boundary residual method have been used for the analysis and optimization of the proposed structure

Phase-matched multi-layer based polarisation-independent spot-size converter for silicon nanowire

The efficient coupling of optical power from a silicon nanowire (NW) to an optical fibre is challenging for both the quasi-TE and quasi-TM polarisations. Here, we propose a polarisation-independent spot-size converter (PI-SSC) based on phase-matched multi-layer waveguides for efficient coupling between a silicon NW and an optical fibre for both the polarisations. The fabrication process of the proposed PI-SSC is compatible with the complementary metal-oxide-semiconductor (CMOS) process. The optimisation for the proposed PI-SSC is studied by using a numerically efficient algorithm, combining a rigorous H-field based full-vectorial finite element method (VFEM) and the least squares boundary residual (LSBR) method. The simulation results show that using an eleven-layer based PI-SSC, the coupling losses between a silicon NW and a lensed fibre of radius 2 μm can be reduced to only 0.34 dB and 0.25 dB for the quasi-TE and quasi-TM polarisations, respectively. Furthermore, the output multi-layer is horizontally tapered, which further reduces the coupling loss for both the polarisations and the end face is easy to be polished

Transmission and group-delay characterization of coupled resonator optical waveguides apodized through the longitudinal offset technique

[EN] In this Letter, the amplitude and group delay characteristics of coupled resonator optical waveguides apodized through the longitudinal offset technique are presented. The devices have been fabricated in silicon-on-insulator technology employing deep ultraviolet lithography. The structures analyzed consisted of three racetracks resonators uniform (nonapodized) and apodized with the aforementioned technique, showing a delay of 5 ± 3 ps and 4 ± 0:5 ps over 1.6 and 1:4 nm bandwidths, respectively. © 2011 Optical Society of America.This work has been funded through the Spanish Plan Nacional de I+D+i 2008-2011 project TEC2008-06145/TEC Coupled Resonator Optical Waveguides eNgineering (CROWN). J. D. Domenech acknowledges the Beca de Formacion de Personal Investigador (FPI) research grant BES-2009-018381.Doménech Gómez, JD.; Muñoz Muñoz, P.; Capmany Francoy, J. (2011). Transmission and group-delay characterization of coupled resonator optical waveguides apodized through the longitudinal offset technique. Optics Letters. 36(2):136-138. doi:10.1364/OL.36.000136S136138362Yariv, A., Xu, Y., Lee, R. K., & Scherer, A. (1999). Coupled-resonator optical waveguide:?a proposal and analysis. Optics Letters, 24(11), 711. doi:10.1364/ol.24.000711Poon, J. K. S., Scheuer, J., Xu, Y., & Yariv, A. (2004). Designing coupled-resonator optical waveguide delay lines. Journal of the Optical Society of America B, 21(9), 1665. doi:10.1364/josab.21.001665Poon, J. K., Zhu, L., DeRose, G. A., & Yariv, A. (2006). Transmission and group delay of microring coupled-resonator optical waveguides. Optics Letters, 31(4), 456. doi:10.1364/ol.31.000456Capmany, J., Muñoz, P., Domenech, J. D., & Muriel, M. A. (2007). Apodized coupled resonator waveguides. Optics Express, 15(16), 10196. doi:10.1364/oe.15.010196Xia, F., Rooks, M., Sekaric, L., & Vlasov, Y. (2007). Ultra-compact high order ring resonator filters using submicron silicon photonic wires for on-chip optical interconnects. Optics Express, 15(19), 11934. doi:10.1364/oe.15.011934Domenech, J. D., Muñoz, P., & Capmany, J. (2009). The longitudinal offset technique for apodization of coupled resonator optical waveguide devices: concept and fabrication tolerance analysis. Optics Express, 17(23), 21050. doi:10.1364/oe.17.021050Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology. (2005). Journal of Lightwave Technology, 23(1), 401-412. doi:10.1109/jlt.2004.834471Xia, F., Sekaric, L., & Vlasov, Y. A. (2006). Mode conversion losses in silicon-on-insulator photonic wire based racetrack resonators. Optics Express, 14(9), 3872. doi:10.1364/oe.14.003872Taillaert, D., Van Laere, F., Ayre, M., Bogaerts, W., Van Thourhout, D., Bienstman, P., & Baets, R. (2006). Grating Couplers for Coupling between Optical Fibers and Nanophotonic Waveguides. Japanese Journal of Applied Physics, 45(8A), 6071-6077. doi:10.1143/jjap.45.6071Capmany, J., & Muriel, M. A. (1990). A new transfer matrix formalism for the analysis of fiber ring resonators: compound coupled structures for FDMA demultiplexing. Journal of Lightwave Technology, 8(12), 1904-1919. doi:10.1109/50.62888Poon, J., Scheuer, J., Mookherjea, S., Paloczi, G. T., Huang, Y., & Yariv, A. (2004). Matrix analysis of microring coupled-resonator optical waveguides. Optics Express, 12(1), 90. doi:10.1364/opex.12.000090Landobasa, Y. M., Darmawan, S., & Chin, M.-K. (2005). Matrix analysis of 2-D microresonator lattice optical filters. IEEE Journal of Quantum Electronics, 41(11), 1410-1418. doi:10.1109/jqe.2005.85706