2019 Passive integrated photonic structures and new platforms

Silicon high performance devices using subwavelength structures (Invited paper)
Robert Halir1,2, Alejandro Sánchez-Postigo1, Jose M. Luque-González1, Alaine Herrero-Bermello3,
Jonas Leuermann2, Alejandro Ortega-Moñux1, Gonzalo Wangüemert-Pérez1,2, Aitor V. Velasco3,
Jose de-Oliva-Rubio1, Jens H. Schmid4, Pavel Cheben4, Jordi Soler Penadés5, Milos Nedeljkovic5,
Goran Z. Mashanovich5, and Íñigo Molina-Fernández1,2
1 Universidad de Málaga, Departamento de Ingeniería de Comunicaciones, ETSI Telecomunicación, Spain
2 Bionand Center for Nanomedicine and Biotechnology, Málaga, Spain
3 Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
4 National Research Council Canada, Ottawa, Ontario, Canada
5 Optoelectronics Research Centre, University of Southampton, Southampton, UK
e-mail: rhalir@uma.es

Silicon photonics is poised to solve challenges in areas such as datacom, environmental monitoring and diagnostics, by leveraging the economies of scale afforded by CMOS manufacturing. This requires a wide variety of integrated silicon devices, including fiber-to-chip couplers, polarization splitters and waveguide couplers, operating both in the near-infrared and the mid-infrared wavelength range. However, the reduced set of materials available in this platform can often limit the performance of these devices. Subwavelength structures enable the synthesis of optical metamaterials, with properties than can be tuned to enhance device performance, by using fully etched silicon structures with a periodicity smaller than the wavelength of light. Here we review the basic operating principles of these structures, discuss how to efficiently model them, and report on the latest advances in this rapidly growing field.
Keywords: silicon photonics, subwavelength structures, dielectric metamaterials, high performance devices

Silicon high performance devices using subwavelength structures

Dual-polarization Ultra-wideband Nanophotonic Beam Splitter
David González Andrade1, Christian Lafforgue2,3, Elena Durán-Valdeiglesias2, Xavier Le Roux2, Mathias Berciano2, Eric Cassan2, Delphine Marris-Morini2, Aitor V. Velasco1, Pavel Cheben4, Laurent Vivien2, Carlos Alonso-Ramos2,*
1 Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28006, Spain
2 Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Sud, Université Paris-Saclay, C2N, Orsay 91405, France
3 École Normale Supérieure Paris-Saclay, Université Paris-Saclay, Cachan 94230, France
4 National Research Council Canada, 1200 Montreal Road, Ottawa, Ontario K1A0R5, Canada
e-mail: Carlos.Ramos@u-psud.fr

High-performance optical beam splitters are of fundamental importance for the development of advanced silicon photonics integrated circuits. However, the performance of state-of-the-art silicon nanophotonic splitters is limited in terms of bandwidth and polarization dependence. Here, we present a new beam splitter approach that exploits modal engineering in slotted waveguides to overcome these limitations, enabling ultra-broadband polarization-insensitive optical power splitting. The proposed splitter relies on a single-mode slot waveguide that is gradually transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate insertion loss and power imbalance lower than 1 dB for both, transverse-electric (TE) and transverse-magnetic (TM) polarizations in an unprecedented bandwidth of 390 nm (1260 – 1650 nm).
Keywords: beam splitter, silicon-on-insulator, ultra-wideband, dual-polarization.

Dual-polarization Ultra-wideband Nanophotonic Beam Splitter

Simulation and Experimental Characterization of Compact Out-of-Plane
Focusing Grating Couplers on 220 nm-SOI platform
(Student paper)
Hanna Becker 1, Clemens J. Krückel 2, Dries Van Thourhout 2, Martijn J.R. Heck 1
1Department of Engineering, Aarhus University, Denmark
2Photonics Research Group, Department of Information Technology, Ghent University – imec
e-mail: hanna.becker@eng.au.dk

We present the design and characterization of compact out-of-plane focusing grating couplers on a silicon photonic platform, based on the fabrication restrictions for standard 193 nm UV lithography.
The characterization by spatially sweeping a lensed fibre across the grating couplers clearly reveals the focusing behaviour and validates the design based on phase matching conditions for the one- and two-dimensional case. To our knowledge, this makes these grating couplers the first experimentally
demonstrated 2D out-of-plane focusing grating couplers on a standard 220 nm-SOI platform. These grating couplers can find application as optical photonic layer couplers in optical sensing, as vertical interconnects, or to address spintronic memory elements.
Keywords: out-of-plane focusing grating couplers, photonic-electronic integration

Simulation and Experimental Characterization of Compact Out-of-Plane Focusing Grating Couplers on 220 nm-SOI platform

Processing free space optical beams with a silicon photonic mesh (Student Paper)
Maziyar Milanizadeh1, Piero Borga1, Francesco Morichetti1, D.A.B. Miller2, Andrea Melloni1
1Dipartimento di Elettronica, Informazione e Bioingegneria – Politecnico di Milano, Milano, 20133 Italy.
2Ginzton Laboratory, Stanford University, Spilker Building, Stanford, CA 94305, USA
mail: maziyar.milanizadeh@polimi.it

Photonic integrated meshes made of tuneable interferometers enable us to implement functions programmable on demand and are being envisioned as the optical counterpart of electronic field programmable gate arrays. Several examples of photonics processors capable of performing arbitrary linear operations have been recently proposed, and are expected to find applications in different areas, from the on-chip processing of telecom signals to microwave photonics, and from quantum optics to neural networks. In this work, we use a reconfigurable mesh of silicon photonic Mach-Zehnder Interferometers (MZIs) to manipulate free-space optical beams. Among the variety of functionalities that can be implemented, we demonstrate beam steering, beam coupling from a free space optical source to a single mode waveguide and automatic identification of the direction of arrival of a beam from a free space source.
Keywords: silicon photonics, reconfigurable photonic integrated circuits, free space optics

Processing free space optical beams with a silicon photonic mesh

Exploring titanium dioxide as a new photonic platform
Manon Lamy, Marie-Maxime Mennemanteuil, Jean-Claude Weeber, Christophe Finot, Kamal Hammani
Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS – Université Bourgogne Franche-Comté, 9 avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France
e-mail: Kamal.Hammani@u-bourgogne.fr

We report the development of titanium dioxide-based waveguides for applications in the near- and mid- infrared. Thanks to embedded metal grating couplers, we demonstrate error free 10 Gbit/s optical transmissions at 1.55 and 2 μm. We also demonstrate octave-spanning supercontinuum in cm-long waveguides. We explore the way to improve such waveguides through optimized fabrication process.
Keywords: Titanium Dioxide waveguides, Integrated optical materials, Optical Communications, Supercontinuum generation, Nonlinear integrated optics

Exploring titanium dioxide as a new photonic platform