Ultra-Broadband Passive Phase Shifter Using Anisotropic Subwavelength Metamaterials
David González-Andrade1,*, José Manuel Luque-González2, J. Gonzalo Wangüemert-Pérez2, Alejandro Ortega-Moñux2, Pavel Cheben3, Íñigo Molina-Fernández2,4, Aitor V. Velasco1
1 Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28006, Spain
2 Departamento de Ingeniería de Comunicaciones, ETSI Telecomunicación, Universidad de Málaga, Málaga 29071, Spain
3 National Research Council Canada, 1200 Montreal Road, Bldg. M50, Ottawa K1A 0R6, Canada
4 Bionand Center for Nanomedicine and Biotechnology, Parque Tecnológico de Andalucía, Málaga 29590, Spain
Optical phase shifters are a cornerstone constituent in most photonic integrated circuits aimed at high-end applications. However, most progress has focused on active phase shifters in recent years, while passive phase shifters have barely evolved. Here, we propose a new type of ultra-broadband passive phase shifter that exploits anisotropy and dispersion engineering in subwavelength metamaterial waveguides. Floquet-Bloch simulations of our proposed device predict a phase shift error below ±1.7° over an outstanding 400 nm bandwidth (1.35 – 1.75 μm). The subwavelength engineered PS was fabricated on an SOI platform and our measurements show a four-fold reduction in the phase variation compared to other conventional phase shifters based on tapered waveguides.
Keywords: phase shifter, silicon-on-insulator, subwavelength grating, metamaterial, ultra-broadband.
Independent phase matching for TE and TM polarization in directional couplers with tilted subwavelength structures (Student Paper)
José Manuel Luque-González1*, Alaine Herrero-Bermello2†, Alejandro Ortega-Moñux1, Marina Sánchez-Rodríguez1, Aitor V. Velasco2, Jens H. Schmid3, Pavel Cheben3, Íñigo Molina-Fernández1,4, Robert Halir1,4
1Universidad de Málaga, Dpto. de Ingeniería de Comunicaciones, ETSI Telecomunicación, Campus de Teatinos s/n, 29071 Málaga, Spain
2Institute of Optics, Spanish National Research Council, 28006 Madrid, Spain
3National Research Council Canada, 1200 Montreal Road, Bldg. M50, Ottawa K1A 0R6, Canada
4Bionand Center for Nanomedicine and Biotechnology, Parque Tecnológico de Andalucía, 29590 Málaga, Spain
†Currently with Alcyon Photonics S.L., Madrid 28006, España
Tilted subwavelength gratings (SWGs) are promising structures for birefringence control and polarization management in integrated photonic waveguides. Here we show how tilted SWGs can be used to design a directional coupler based polarization beam splitter which is symmetric for TM polarization but asymmetric for TE polarization. Using this approach, we develop a polarization beam splitter with calculated insertion loss below 1 dB and an extinction ratio better than 20 dB over a bandwidth of 86 nm. The fabricated device shows negligible insertion loss and an extinction ratio over 15 dB over a bandwidth of 72 nm.
Keywords: Photonic integrated devices, polarization management, subwavelength gratings.
Dual-metamaterial silicon micro-ring resonators (Student Paper)
T. T. D. Dinh1, X. Le Roux1, J. Zhang1, M. Montesinos1, C. Lafforgue1,2, D. Benedikovic1, P. Cheben3,4, E. Cassan1, D. Marris-Morini1, L. Vivien1, and C. Alonso-Ramos1
1 Universite Paris-Saclay, Univ. Paris-Sud, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120, Palaiseau, France
2 École Normale Supérieure Paris-Saclay, Université Paris-Saclay, 94230 Cachan, France
3 National Research Council Canada, ON K1A0R6 Ottawa, Canada
4 Center for Research in Photonics, University of Ottawa, Ottawa K1N6N5, Canada
Subwavelength metamaterial engineering has opened exciting prospects for controlling and manipulating light in silicon photonic waveguides. Most state-of-the-art subwavelength photonic waveguides rely on periodic nanostructuration of the core or the cladding, but not both. Here, we present a new waveguide geometry that exploits metamaterial engineering of the core and the cladding, independently. By implementing two metamaterials, this step-index geometry provides unique flexibility in the design of the waveguide index contrast. The proposed approach opens additional degrees of freedom to shape single-mode condition and to control modal confinement in the vertical and horizontal directions. Hence, the proposed dual-metamaterial waveguide geometry has a great potential for applications requiring optimized light-matter interactions such as sensing, hybrid integration or nonlinear wavelength conversion. As a proof-of-concept, we experimentally demonstrate dual-metamaterial micro-ring resonators in the 220-nm-thick Si technology with quality factors in excess of 50000 near 1550 nm wavelength.
Keywords: silicon photonics, subwavelength, light-matter interactions, sensing.
Bridging the Graded-Index Few-Mode Fibre with Photonic Integrated Circuits via Efficient Diffraction Waveguide Gratings (Student Paper)
Yeyu Tong1, Xuetong Zhou1, Yi Wang1, Chi-Wai Chow2 and Hon Ki Tsang1*
1 Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong, P.R. China
2Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan
Spatial-division multiplexing (SDM) employing few-mode fibres (FMF) has attracted much interest for increasing the capacity of optical fibre communication systems. Graded-index few-mode fibres (GI-FMF) have low modal differential group delay (DGD), allowing extended transmission distance and bandwidth. In this paper, we describe novel efficient waveguide grating couplers fabricated on the silicon photonic platform for selectively launching different modes in the GI-FMF. The waveguide grating couplers may be integrated with transceivers for implementing mode division multiplexing in the fibre communications. The single-polarization diffraction waveguide gratings is measured to have coupling efficiencies into the LP01 mode and LP11 mode of – 2.8 dB and – 3.88 dB, respectively. The measured 3-dB bandwidth of the two modes are 61.2 nm and 59.0 nm. A twodimensional grating based on the effective medium theory (EMT) is also demonstrated, supporting totally four optical channels including the two orthogonal polarizations of the LP01 mode and LP11 mode. The obtained peak coupling efficiency is – 4.89 dB for LP01 mode and – 5.71 dB for LP11 mode. The 3-dB bandwidth of the two modes are 23.2 nm and 21.6 nm, respectively.
Keywords: Integrated optics, silicon photonics, diffraction gratings, spatial-division multiplexing.
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