publications | Abdelfettah Hadij-ElHouati

This list is updated automatically every week from my ORCID record.

2024

Opt. Express
Ultra-efficient surface grating couplers for chip-to-fiber and chip-to-free-space coupling based on single-beam radiation

Alejandro Sánchez-Postigo, Pablo Ginel-Moreno, Jens H. Schmid, and 6 more authors

Optics Express, Nov 2024

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Surface grating couplers, such as fiber-chip grating couplers and optical antennas, are fundamental devices in photonic integrated circuits, as they enable the coupling of light between the chip and an external medium. An important metric of surface grating couplers is the coupling efficiency, and high values, greater than -1 dB, are required for applications in quantum technology, light detection and ranging, and optical interconnects. Surface grating couplers typically suffer from radiation loss to the substrate, which significantly limits their coupling efficiency. Here we propose a novel grating-coupling concept that utilizes a high-refractive-index upper cladding to frustrate radiation orders to the substrate by operating in a single-beam diffraction regime. To illustrate this concept, we report the design of an easily fabricable silicon surface grating coupler with an unprecedented coupling efficiency of -0.2 dB to a single-mode optical fiber. Furthermore, the proposed strategy allows us to design an evanescently coupled millimeter-long optical antenna with a coupling efficiency of -0.1 dB to free space. Additionally, an ultra-fast wavelength-tunable beam steering of 0.37°/nm is achieved, which corresponds to more than a 2.5-fold enhancement over comparable silicon antennas. These results represent a pathway for a new set of photonic integrated interfaces for applications in which high-efficiency chip-to-fiber and chip-to-free-space coupling is critical.
@article{sanchezpostigo2024ultra, title = {Ultra-efficient surface grating couplers for chip-to-fiber and chip-to-free-space coupling based on single-beam radiation}, author = {Sánchez-Postigo, Alejandro and Ginel-Moreno, Pablo and Schmid, Jens H. and Hadij-ElHouati, Abdelfettah and Ortega-Moñux, Alejandro and Gonzalo Wangüemert-Pérez, J. and Halir, Robert and Cheben, Pavel and Molina-Fernández, Íñigo}, journal = {Optics Express}, publisher = {Optica Publishing Group}, volume = {32}, number = {23}, pages = {41156}, year = {2024}, month = nov, doi = {10.1364/oe.537342}, }

2023

Opt. Express
Thermally induced sideband generation in silicon-on-insulator cladding modulated Bragg notch filters

Carlos Pérez-Armenta, Kevan K. MacKay, Abdelfettah Hadij-ElHouati, and 6 more authors

Optics Express, Jun 2023

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We investigate and experimentally demonstrate a cladding modulated Bragg grating superstructure as a dynamically tunable and reconfigurable multi-wavelength notch filter. A non-uniform heater element was implemented to periodically modulate the effective index of the grating. The Bragg grating bandwidth is controlled by judiciously positioning loading segments away from the waveguide core, resulting in a formation of periodically spaced reflection sidebands. The thermal modulation of a periodically configured heater elements modifies the waveguide effective index, where an applied current controls the number and intensity of the secondary peaks. The device was designed to operate in TM polarization near the central wavelength of 1550 nm and was fabricated on a 220-nm silicon-on-insulator platform, using titanium-tungsten heating elements and aluminum interconnects. We experimentally demonstrate that the Bragg grating self-coupling coefficient can be effectively controlled in a range from 7 mm -1 to 110 mm -1 by thermal tuning, with a measured bandgap and sideband separation of 1 nm and 3 nm, respectively. The experimental results are in excellent agreement with simulations.
@article{perezarmenta2023thermally, title = {Thermally induced sideband generation in silicon-on-insulator cladding modulated Bragg notch filters}, author = {Pérez-Armenta, Carlos and MacKay, Kevan K. and Hadij-ElHouati, Abdelfettah and Ortega-Moñux, A. and Molina-Fernández, I. and Wangüemert-Pérez, J. Gonzalo and Schmid, Jens H. and Cheben, Pavel and Ye, Winnie N.}, journal = {Optics Express}, publisher = {Optica Publishing Group}, volume = {31}, number = {13}, pages = {22225}, year = {2023}, month = jun, doi = {10.1364/oe.488108}, }

2022

PhD Thesis
Highly efficient distributed Bragg deflectors for silicon photonic waveguide devices

Abdelfettah Hadij-ElHouati

Universidad de Málaga, 2022

Abs Bib

This thesis focuses on the comprehensive study of integrated photonic couplers pertaining to the category of distributed Bragg deflectors (DBDs) and their implementation in the silicon-on-insulator (SOI) platform. This device converts a channel waveguide mode into a slab confined beam by using a grating formed in the waveguide core. The DBD was first proposed by Stoll in 1978. Stoll foresaw a multitude of applications of DBDs including beam expansion, polarization filtering, beam splitting and modulation. However, DBDs have typically suffered from high insertion losses that hindered their use in practical applications. In this thesis, we develop strategies to dramatically reduce the excess loss and demonstrate various low-loss DBD-based devices in the SOI platform. First, we developed various tools and methodologies for efficient analysis and design of DBD-based devices. Then, by using these new tools, we found out that off-chip radiation was the primary factor responsible for the excess loss observed in previous works. Subsequently, we propose and develop an original design method based on the single-beam condition, which efficiently suppresses off-chip radiation thus yielding low-loss DBD devices. Based on these original approaches, a low-loss wavelength demultiplexer was designed and experimentally demonstrated. Demultiplexer thermal tunability and flattop response have also been investigated. Finally, we explored the use of DBD devices as feeding elements for grating-based surface-emitting antennas, an application that allows efficient generation of large-area and highly-directional free space beams generated on-chip.
@phdthesis{hadijelhouati2023thesis, title = {Highly efficient distributed Bragg deflectors for silicon photonic waveguide devices}, author = {Hadij-ElHouati, Abdelfettah}, school = {Universidad de Málaga}, publisher = {UMA Editorial}, year = {2022}, url = {https://hdl.handle.net/10630/25858}, }

2021

Conference

Integrated metamaterial surface-emitting antenna for beam steering applications

Pablo Ginel-Moreno, Alejandro Sanchez-Postigo, Jose de-Oliva-Rubio, and 7 more authors

In 2021 IEEE 17th International Conference on Group IV Photonics (GFP), Dec 2021

Abs DOI Bib

Integrated optical antennas are relevant devices for the development of next-generation LIDAR systems. Here we experimentally demonstrate a new topology to implement long antennas in silicon-on-insulator platform. The designed 2-millimeter-long antenna presents a measured far-field beam divergence of 0.1° and a wavelength sensitivity of 0.13°/nm.

@inproceedings{ginelmoreno2021integrated,
  title = {Integrated metamaterial surface-emitting antenna for beam steering applications},
  author = {Ginel-Moreno, Pablo and Sanchez-Postigo, Alejandro and de-Oliva-Rubio, Jose and Hadij-ElHouati, Abdelfettah and Ye, Winnie N. and Wanguemert-Perez, J. Gonzalo and Molina-Fernandez, Inigo and Schmid, Jens H. and Cheben, Pavel and Ortega-Monux, Alejandro},
  booktitle = {2021 IEEE 17th International Conference on Group IV Photonics (GFP)},
  publisher = {IEEE},
  pages = {1-2},
  year = {2021},
  month = dec,
  doi = {10.1109/gfp51802.2021.9673881},
}

Opt. Lett.
Low-loss off-axis curved waveguide grating demultiplexer

Abdelfettah Hadij-ElHouati, Alejandro Ortega-Moñux, J. Gonzalo Wangüemert-Pérez, and 5 more authors

Optics Letters, Oct 2021

Abs DOI Bib

Current optical communication systems rely on the use of wavelength division multiplexing (WDM) to keep up with the increasing data rate requirements. The wavelength demultiplexer is the key component to implement WDM systems. In this Letter, we design and experimentally demonstrate a demultiplexer based on a curved grating waveguide geometry that separates eight channels with a spacing of 10 nm (1249 GHz) around the central wavelength of 1550 nm. The fabricated device shows very low insertion loss ( ∼ 1 d B ) and a crosstalk (XT) below − 25 d B . This device leverages metamaterial index engineering to implement the lateral cladding on one side of the waveguide. This makes it possible to design a waveguide grating with highly directional lateral emission by operating in a regime where diffraction into the silica upper cladding is frustrated, thus suppressing losses due to off-chip radiation.
@article{hadijelhouati2021loss, title = {Low-loss off-axis curved waveguide grating demultiplexer}, author = {Hadij-ElHouati, Abdelfettah and Ortega-Moñux, Alejandro and Wangüemert-Pérez, J. Gonzalo and Halir, Robert and Wang, Shurui and Schmid, Jens H. and Cheben, Pavel and Molina-Fernández, I.}, journal = {Optics Letters}, publisher = {Optica Publishing Group}, volume = {46}, number = {19}, pages = {4821}, year = {2021}, month = oct, doi = {10.1364/ol.434294}, }
Nanophotonics
A review of silicon subwavelength gratings: building break‐through devices with anisotropic metamaterials

José Manuel Luque‐González, Alejandro Sánchez‐Postigo, Abdelfettah Hadij‐ElHouati, and 6 more authors

Nanophotonics, Sep 2021

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Silicon photonics is playing a key role in areas as diverse as high‐speed optical communications, neural networks, supercomputing, quantum photonics, and sensing, which demand the development of highly efficient and compact light‐processing devices. The lithographic segmentation of silicon waveguides at the subwavelength scale enables the synthesis of artificial materials that significantly expand the design space in silicon photonics. The optical properties of these metamaterials can be controlled by a judicious design of the subwavelength grating geometry, enhancing the performance of nanostructured devices without jeopardizing ease of fabrication and dense integration. Recently, the anisotropic nature of subwavelength gratings has begun to be exploited, yielding unprecedented capabilities and performance such as ultrabroadband behavior, engineered modal confinement, and sophisticated polarization management. Here we provide a comprehensive review of the field of subwavelength metamaterials and their applications in silicon photonics. We first provide an in‐depth analysis of how the subwavelength geometry synthesizes the metamaterial and give insight into how properties like refractive index or anisotropy can be tailored. The latest applications are then reviewed in detail, with a clear focus on how subwavelength structures improve device performance. Finally, we illustrate the design of two ground‐breaking devices in more detail and discuss the prospects of subwavelength gratings as a tool for the advancement of silicon photonics.
@article{luquegonzalez2021review, title = {A review of silicon subwavelength gratings: building break‐through devices with anisotropic metamaterials}, author = {Luque‐González, José Manuel and Sánchez‐Postigo, Alejandro and Hadij‐ElHouati, Abdelfettah and Ortega‐Moñux, Alejandro and Wangüemert‐Pérez, J. Gonzalo and Schmid, Jens H. and Cheben, Pavel and Molina‐Fernández, Íñigo and Halir, Robert}, journal = {Nanophotonics}, publisher = {Wiley}, volume = {10}, number = {11}, pages = {2765-2797}, year = {2021}, month = sep, doi = {10.1515/nanoph-2021-0110}, }
Opt. Lett.
Millimeter-long metamaterial surface-emitting antenna in the silicon photonics platform

Pablo Ginel-Moreno, Alejandro Sánchez-Postigo, José de-Oliva-Rubio, and 7 more authors

Optics Letters, Aug 2021

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Integrated optical antennas are key components for on-chip light detection and ranging technology (LIDAR). In order to achieve a highly collimated far field with reduced beam divergence, antenna lengths on the order of several millimeters are required. In the high-index contrast silicon photonics platform, achieving such long antennas typically demands weakly modulated gratings with lithographic minimum feature sizes below 10 nm. Here, we experimentally demonstrate a new, to the best of our knowledge, strategy to make long antennas in silicon waveguides using a metamaterial subwavelength grating (SWG) waveguide core loaded with a lateral periodic array of radiative elements. The mode field confinement is controlled by the SWG duty cycle, and the delocalized propagating mode overlaps with the periodic perturbations. With this arrangement, weak antenna radiation strength can be achieved while maintaining a minimum feature size as large as 80 nm. Using this strategy, we experimentally demonstrate a 2-millimeter-long, single-etched subwavelength-engineered optical antenna on a conventional 220 nm SOI platform, presenting a measured far-field beam divergence of 0.1° and a wavelength scanning sensitivity of 0.13°/nm.
@article{ginelmoreno2021millimeter, title = {Millimeter-long metamaterial surface-emitting antenna in the silicon photonics platform}, author = {Ginel-Moreno, Pablo and Sánchez-Postigo, Alejandro and de-Oliva-Rubio, José and Hadij-ElHouati, Abdelfettah and Ye, Winnie N. and Wangüemert-Pérez, J. Gonzalo and Molina-Fernández, Íñigo and Schmid, Jens H. and Cheben, Pavel and Ortega-Moñux, Alejandro}, journal = {Optics Letters}, publisher = {Optica Publishing Group}, volume = {46}, number = {15}, pages = {3733}, year = {2021}, month = aug, doi = {10.1364/ol.431983}, }
Opt. Lett.
High-efficiency conversion from waveguide mode to an on-chip beam using a metamaterial engineered Bragg deflector

Abdelfettah Hadij-ElHouati, Pavel Cheben, Alejandro Ortega-Moñux, and 5 more authors

Optics Letters, May 2021

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Diffraction gratings that redirect light propagating in a channel waveguide to an on-chip slab are emerging as important building blocks in integrated photonics. Such distributed Bragg deflectors enable precise shaping of slab confined beams for a variety of applications, including wavelength multiplexing, optical phased array feeding, and coupling interfaces for on-chip point-to-point communications. However, these deflectors suffer from significant losses caused by off-chip radiation. In this Letter, we show, for the first time, to the best of our knowledge, that off-chip radiation can be dramatically reduced by using the single-beam phase matching condition and subwavelength metamaterial refractive index engineering. We present a deflector design with losses below 0.3 dB, opening a path toward new applications of distributed Bragg deflectors in integrated photonics.
@article{hadijelhouati2021high, title = {High-efficiency conversion from waveguide mode to an on-chip beam using a metamaterial engineered Bragg deflector}, author = {Hadij-ElHouati, Abdelfettah and Cheben, Pavel and Ortega-Moñux, Alejandro and Wangüemert-Pérez, J. Gonzalo and Halir, Robert and de-Oliva-Rubio, José and Schmid, Jens H. and Molina-Fernández, Iñigo}, journal = {Optics Letters}, publisher = {Optica Publishing Group}, volume = {46}, number = {10}, pages = {2409}, year = {2021}, month = may, doi = {10.1364/ol.420993}, }
Opt. Express
Complex spectral filters in silicon waveguides based on cladding-modulated Bragg gratings

Daniel Pereira-Martín, José Manuel Luque-González, J. Gonzalo Wangüemert-Pérez, and 8 more authors

Optics Express, May 2021

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Spectral filters are important building blocks for many applications in integrated photonics, including datacom and telecom, optical signal processing and astrophotonics. Sidewall-corrugated waveguide grating is typically the preferred option to implement spectral filters in integrated photonic devices. However, in the high-index contrast silicon-on-insulator (SOI) platform, designs with corrugation sizes of only a few tens of nanometers are often required, which hinders their fabrication. In this work, we propose a novel geometry to design complex Bragg filters with an arbitrary spectral response in silicon waveguides with laterally coupled Bragg loading segments. The waveguide core is designed to operate with a delocalized mode field, which helps reduce sensitivity to fabrication errors and increase accuracy on synthesized coupling coefficients and the corresponding spectral shape control. We present an efficient design strategy, based on the layer-peeling and layer-adding algorithms, that allows to readily synthesize an arbitrary target spectrum for our cladding-modulated Bragg gratings. The proposed filter concept and design methodology are validated by designing and experimentally demonstrating a complex spectral filter in an SOI platform, with 20 non-uniformly spaced spectral notches with a 3-dB linewidth as small as 210 pm.
@article{pereiramartin2021complex, title = {Complex spectral filters in silicon waveguides based on cladding-modulated Bragg gratings}, author = {Pereira-Martín, Daniel and Luque-González, José Manuel and Gonzalo Wangüemert-Pérez, J. and Hadij-ElHouati, Abdelfettah and Molina-Fernández, Íñigo and Cheben, Pavel and Schmid, Jens H. and Wang, Shurui and Ye, Winnie N. and Čtyroký, Jiří and Ortega-Moñux, Alejandro}, journal = {Optics Express}, publisher = {Optica Publishing Group}, volume = {29}, number = {11}, pages = {15867}, year = {2021}, month = may, doi = {10.1364/oe.420696}, }
Conference
Subwavelength metamaterials: the path towards next-generation silicon photonic devices.

Robert Halir, Jose Manuel Luque-González, Alejandro Sánchez-Postigo, and 19 more authors

In Integrated Optics: Design, Devices, Systems and Applications VI, Apr 2021

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Silicon photonic waveguides patterned at the subwavelength level behave as metamaterials whose optical properties, including refractive index, dispersion and anisotropy can be tuned by judiciously designing the subwavelength geometry. Over the past years, the added design freedom afforded by these structures has enabled a wide variety of novel high performance devices, ranging from high efficiency fibre-to-chip couplers, to on-chip polarization and mode management, and ultra-broadband waveguide couplers covering several optical communication bands. In this invited keynote talk we will revisit the physical foundations of these structures, explore some of the latest advances in the field with applications in both telecommunications and sensing, and discuss some of the outstanding challenges to move these structures from research labs to large-scale commercialisation.
@inproceedings{halir2021subwavelength, title = {Subwavelength metamaterials: the path towards next-generation silicon photonic devices.}, author = {Halir, Robert and Luque-González, Jose Manuel and Sánchez-Postigo, Alejandro and Pérez-Armenta, Carlos and Ginel-Moreno, Pablo and Hadij-ElHouati, Abdelfettah and Pereira-Martin, Daniel and Torres-Cubillo, Antonia and Leuermann, Jonas and de Oliva Rubio, Jose and Wangüemert-Pérez, Juan Gonzalo and Ortega-Moñux, Alejandro and Molina-Fernández, Íñigo and Schmid, Jens and Cheben, Pavel and Ctyroky, Jiri and Villafranca Velasco, Aitor and Herrero-Bermello, Alaine and González-Andrade, David and Dias-Ponte, Antonio and Nedeljkovic, Milos and Mashanovich, Goran}, booktitle = {Integrated Optics: Design, Devices, Systems and Applications VI}, publisher = {SPIE}, pages = {6}, year = {2021}, month = apr, doi = {10.1117/12.2589054}, }
Conference
Subwavelength grating silicon photonic devices

Iñigo Molina-Fernández, Abdelfettah Hadij-Elhouati, José Manuel Luque-González, and 9 more authors

In Silicon Photonics XVI, Mar 2021

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Periodic silicon waveguides with a pitch that is below half the effective wavelength of light support diffraction-less Bloch modes. These modes propagate as through a homogeneous, artificial-core metamaterial waveguide whose optical characteristics can be engineered by lithographic patterning. Subwavelength gratings (SWGs) provide designers with unique tools to control the refractive index, dispersion and birefringence of the equivalent metamaterial, yielding improved device performance. Based on this approach many high-performance optical devices have been designed and experimentally demonstrated in the last years. In this paper we will review the fundamentals of SWG engineering and present some of our latest findings.
@inproceedings{molinafernandez2021subwavelength, title = {Subwavelength grating silicon photonic devices}, author = {Molina-Fernández, Iñigo and Hadij-Elhouati, Abdelfettah and Luque-González, José Manuel and Pereira, Daniel and Sánchez Postigo, Alejandro and Wangüenmert-Perez, Gonzalo and Ortega-Moñux, Alejandro and Halir, Robert and de Oliva Rubio, Jose and Schmid, Jens H. and Cheben, Pavel and Ctyroký, Jiri}, booktitle = {Silicon Photonics XVI}, publisher = {SPIE}, pages = {6}, year = {2021}, month = mar, doi = {10.1117/12.2577455}, }

EPJ Web Conf.

Building high-performance integrated optical devices using subwavelength grating metamaterials -INVITED

Alejandro Sánchez-Postigo, Pablo Ginel-Moreno, Alejandro Ortega-Moñux, and 14 more authors

EPJ Web of Conferences, 2021

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The use of subwavelength grating structures in silicon waveguides have fuelled the development of integrated optical components with superior performance. By a judicious lithographic patterning of the grating, the optical properties of the synthesized metamaterial can be accurately tailored. In this work, we review our latest advances in subwavelength-grating-engineered silicon and germanium planar devices.

@article{sanchezpostigo2021building,
  title = {Building high-performance integrated optical devices using subwavelength grating metamaterials -INVITED},
  author = {Sánchez-Postigo, Alejandro and Ginel-Moreno, Pablo and Ortega-Moñux, Alejandro and Wangüemert-Pérez, J. Gonzalo and Halir, Robert and Pereira-Martín, Daniel and Hadij-ElHouati, Abdelfettah and Schmid, Jens H. and Wang, Shurui and Vachon, Martin and Xu, Dan-Xia and Ye, Winnie N. and Soler Penadés, Jordi and Nedeljkovic, Milos and Mashanovich, Goran Z. and Cheben, Pavel and Molina-Fernández, Íñigo},
  journal = {EPJ Web of Conferences},
  publisher = {EDP Sciences},
  volume = {255},
  pages = {01001},
  year = {2021},
  doi = {10.1051/epjconf/202125501001},
}

2020

Opt. Lett.
Highly efficient optical antenna with small beam divergence in silicon waveguides

Pablo Ginel-Moreno, Daniel Pereira-Martín, Abdelfettah Hadij-ElHouati, and 10 more authors

Optics Letters, Oct 2020

Abs DOI Bib

Optical antennas are key components in optical phased arrays for light detection and ranging technology requiring long sensing range and high scanning resolution. To achieve a narrow beam width in the far-field region, antenna lengths of several millimeters or more are required. To date, such long antennas have been impossible to achieve in silicon waveguides because currently demonstrated technologies do not allow accurate control of grating strength. Here, we report on a new type of surface-emitting silicon waveguide with a dramatically increased antenna length of L = 3.65 m m . This is achieved by using a subwavelength metamaterial waveguide core evanescently coupled with radiative segments laterally separated from the core. This results in a far-field diffracted beam width of 0.025°, which is a record small beam divergence for a silicon photonics surface-emitting device. We also demonstrate that by using a design with L -shaped surface-emitting segments, the radiation efficiency of the antenna can be substantially increased compared to a conventional design, with an efficiency of 72% at the wavelength of 1550 nm.
@article{ginelmoreno2020highly, title = {Highly efficient optical antenna with small beam divergence in silicon waveguides}, author = {Ginel-Moreno, Pablo and Pereira-Martín, Daniel and Hadij-ElHouati, Abdelfettah and Ye, Winnie N. and Melati, Daniele and Xu, Dan-Xia and Janz, Siegfried and Ortega-Moñux, Alejandro and Wangüemert-Pérez, J. Gonzalo and Halir, Robert and Molina-Fernández, Íñigo and Schmid, Jens H. and Cheben, Pavel}, journal = {Optics Letters}, publisher = {Optica Publishing Group}, volume = {45}, number = {20}, pages = {5668}, year = {2020}, month = oct, doi = {10.1364/ol.404012}, }
Conference
Metamaterial engineered C+L band 90° hybrid with 150 nm feature size

Abdelfettah Hadij-ElHouati, Robert Halir, Alejandro Ortega-Monux, and 5 more authors

In 2020 IEEE Photonics Conference (IPC), Sep 2020

Abs DOI Bib

90° hybrids are important components for coherent optical communications. Conventional implementations only cover the C band, while broadband, metamaterial-based devices require sub-100nm feature sizes. We propose a design based on dual-etch silicon subwavelength structures that achieves a 170 nm bandwidth with deep-UV compatible feature sizes.
@inproceedings{hadijelhouati2020metamaterial, title = {Metamaterial engineered C+L band 90° hybrid with 150 nm feature size}, author = {Hadij-ElHouati, Abdelfettah and Halir, Robert and Ortega-Monux, Alejandro and Wanguemert-Perez, J. Gonzalo and Podmore, Hugh and Schmid, Jens H. and Cheben, Pavel and Molina-Fernandez, Inigo}, booktitle = {2020 IEEE Photonics Conference (IPC)}, publisher = {IEEE}, pages = {1-2}, year = {2020}, month = sep, doi = {10.1109/ipc47351.2020.9252391}, }

Conference

Subwavelength silicon photonics : Keynote presentation

R. Halir, J. M. Luque-Gonzalez, A. Sanchez-Postigo, and 14 more authors

In 2020 Photonics North (PN), May 2020

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Subwavelength structures are enabling a host of high-performances devices in the silicon photonic platform. Here we review our progress in the field, with an emphasis on the auspicious anisotropic properties of these structures for applications ranging from broadband on-chip GRIN-lenses, to zero-birefringence waveguides and polarization splitters.

@inproceedings{halir2020subwavelength,
  title = {Subwavelength silicon photonics : Keynote presentation},
  author = {Halir, R. and Luque-Gonzalez, J. M. and Sanchez-Postigo, A. and Leuermann, J. and Hadij-ElHouati, A. and Pereira-Martin, D. and de-Oliva-Rubio, J. and Wanguemert-Perez, J. G. and Ortega-Monux, A. and Molina-Fernandez, I. and Schmid, Jens H. and Cheben, Pavel and Andrade, D. Gonzalez and Velasco, A. V. and Herrero-Bermello, A. and Dias-Ponte, A. and Ctyroky, J.},
  booktitle = {2020 Photonics North (PN)},
  publisher = {IEEE},
  pages = {1-1},
  year = {2020},
  month = may,
  doi = {10.1109/pn50013.2020.9166943},
}

Conference
Subwavelength grating metamaterial structures for integrated photonics

Iñigo Molina-Fernández, Gonzalo Wangüemert-Perez, Alejandro Ortega-Moñux, and 12 more authors

In Smart Photonic and Optoelectronic Integrated Circuits XXII, Feb 2020

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Integrated photonics devices, based in subwavelength grating (SWG) metamaterials, have shown unprecedented performance in a wide variety of situations. Since their proposal and first experimental demonstration in 2010 designers have made use of the new degrees of freedom provided by these structures to design advanced devices with improved capabilities. The extended design space provided by SWG structures has been successfully used to engineer the refractive index, the dispersion and, more recently, the waveguide birefringence, thus allowing novel advanced device design. In this invited talk we will review some of the advances made by our group in the field
@inproceedings{molinafernandez2020subwavelength, title = {Subwavelength grating metamaterial structures for integrated photonics}, author = {Molina-Fernández, Iñigo and Wangüemert-Perez, Gonzalo and Ortega-Moñux, Alejandro and Halir, Robert and de Oliva Rubio, Jose and Sánchez Postigo, Alejandro and Luque-González, José Manuel and Hadif-ElHouati, Abdelfettah and Pereira-Martín, Daniel and González-Andrade, David and Villafranca-Velasco, Aitor and Herrero-Bermello, Alaine and Schmid, Jens H. and Cheben, Pavel and Ctyroký, Jirí}, booktitle = {Smart Photonic and Optoelectronic Integrated Circuits XXII}, publisher = {SPIE}, pages = {18}, year = {2020}, month = feb, doi = {10.1117/12.2545061}, }
Conference
Silicon subwavelength waveguiding devices

Iñigo Molina-Fernández, Juan G. Wangüemert-Perez, Alejandro Ortega-Moñuz, and 12 more authors

In High Contrast Metastructures IX, Feb 2020

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Silicon photonics has emerged as an intense field of research due to its unique capabilities to integrate photonics and electronics into the same platform using standard semiconductor fabrication facilities. Subwavelength grating (SWG) structures, i.e. periodic nanostructured waveguides with a pitch below half the wavelength of light, allow the lossless propagation of Bloch-Floquet modes which closely resemble propagation through a homogenous waveguide with optical properties (refractive index, dispersion, birefringence) that can be tailored to fulfill specific design goals. SWG engineering is now routinely used for novel and advanced device design. Fiber-chip couplers, polarization and mode multiplexers, multimode interference couplers (MMIs), lenses, and bragg filters have been successfully designed in our group based in these concepts. In this invited talk we will review some of our last advances in the field.
@inproceedings{molinafernandez2020silicon, title = {Silicon subwavelength waveguiding devices}, author = {Molina-Fernández, Iñigo and Wangüemert-Perez, Juan G. and Ortega-Moñuz, Alejandro and Halir, Robert and de Oliva Rubio, Jose and Sánchez-Postigo, Alejandro and Luque-González, José M. and Hadij-Elhouati, Abdelfettah and Pereira-Martín, Daniel and Gonzalez-Andrade, David and Velasco, Aitor V. and Herrero-Bermello, Alaine and Schmid, Jens H. and Cheben, Pavel and Čtyroký, Jiry}, booktitle = {High Contrast Metastructures IX}, publisher = {SPIE}, pages = {54}, year = {2020}, month = feb, doi = {10.1117/12.2545455}, }

Conference

Silicon subwavelength structures: practical metamaterials for communications and sensing

R. Halir, A. Herrero-Bermello, J.M. Luque-González, and 16 more authors

In Optics InfoBase Conference Papers, 2020

Bib

@inproceedings{halir2020silicon,
  title = {Silicon subwavelength structures: practical metamaterials for communications and sensing},
  author = {Halir, R. and Herrero-Bermello, A. and Luque-González, J.M. and González-Andrade, D. and Leuermann, J. and Sánchez-Postigo, A. and Hadij-ElHouati, A. and Pereira-Martín, D. and de-Oliva-Rubio, J. and Wangüemert-Pérez, J.G. and Ortega-Moñux, A. and Schmid, J.H. and Velasco, A.V. and Dias-Ponte, A. and Ctyroký, J. and Nedeljkovic, M. and Mashanovich, G.Z. and Cheben, P. and Molina-Fernández, Í.},
  booktitle = {Optics InfoBase Conference Papers},
  year = {2020},
  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-85095416760&partnerID=MN8TOARS},
}

2019

Opt. Express
Distributed Bragg deflector coupler for on-chip shaping of optical beams

Abdelfettah Hadij-ElHouati, Pavel Cheben, Alejandro Ortega-Moñux, and 4 more authors

Optics Express, Nov 2019

Abs DOI Bib

In integrated optical circuits light typically travels in waveguides which provide both vertical and horizontal confinement, enabling efficient routing between different parts of the chip. However, for a variety of applications, including on-chip wireless communications, steerable phased arrays or free-space inspired integrated optics, optical beams that can freely propagate in the horizontal plane of a 2D slab waveguide are advantageous. Here we present a distributed Bragg deflector that enables well controlled coupling from a waveguide mode to such a 2D on-chip beam. The device consists of a channel waveguide and a slab waveguide region separated by a subwavelength metamaterial spacer to prevent uncontrolled leakage of the guided mode. A blazed grating in the waveguide sidewall is used to gradually diffract light into the slab region. We develop a computationally efficient strategy for designing gratings that generate arbitrarily shaped beams. As a proof-of-concept we design, in the silicon-on-insulator platform, a compact ×75 Gaussian beam expander and a partial beam deflector. For the latter, we also demonstrate a prototype device with experimental results showing good agreement with our theoretical predictions. We also demonstrate via a rigorous simulation that two such couplers in a back-to-back configuration efficiently couple light, suggesting that these devices can be used as highly directive antennas in the chip plane.
@article{hadijelhouati2019distributed, title = {Distributed Bragg deflector coupler for on-chip shaping of optical beams}, author = {Hadij-ElHouati, Abdelfettah and Cheben, Pavel and Ortega-Moñux, Alejandro and Wangüemert-Pérez, J. Gonzalo and Halir, Robert and Schmid, Jens H. and Molina-Fernández, Íñigo}, journal = {Optics Express}, publisher = {Optica Publishing Group}, volume = {27}, number = {23}, pages = {33180}, year = {2019}, month = nov, doi = {10.1364/oe.27.033180}, }

Conference

Efficient Floquet-Bloch analysis of electrically long quasi-periodic devices

A. Hadij-ElHouati, P. Cheben, A. Ortega-Moñux, and 4 more authors

In XXVII International Workshop on Optical Waveguide Theory and Numerical Modelling (OWTNM), May 2019

Bib

@inproceedings{hadijelhouati2019efficient,
  title = {Efficient Floquet-Bloch analysis of electrically long quasi-periodic devices},
  author = {Hadij-ElHouati, A. and Cheben, P. and Ortega-Moñux, A. and Wangüemert-Pérez, J. G. and Halir, R. and Schmid, J. H. and Molina-Fernández, Í.},
  booktitle = {XXVII International Workshop on Optical Waveguide Theory and Numerical Modelling (OWTNM)},
  year = {2019},
  month = may,
}

Conference
Diffractive sidewall grating coupler: towards 2D free-space optics on chip

Abdelfettah Hadij-ElHouati, Pavel Cheben, Alejandro Ortega-Moñux, and 4 more authors

In Integrated Optics: Design, Devices, Systems, and Applications V, Apr 2019

Abs DOI Bib

Silicon photonics has been the subject of intense research efforts. In order to implement complex integrated silicon photonic devices and systems, a wide range of robust building blocks is needed. Waveguide couplers are fundamental devices in integrated optics, enabling different functionalities such as power dividers, spot-size converters, coherent hybrids and fiber-chip coupling interfaces, to name a few. In this work we propose a new type of nanophotonic coupler based on sidewall grating (SIGRA) concept. SIGRAs have been used in the Bragg regime, for filtering applications, as well as in the sub-wavelength regime in multimode interference (MMI) couplers. However, the use of SIGRAs in the radiation regime has been very limited. Specifically, a coarse wavelength division multiplexer was proposed and experimentally validated. In this work we study the use of SIGRAs in the diffractive regime as a mean to couple the light between a silicon wire waveguide mode and a continuum of slab waveguide modes. We also propose an original technique for designing SIGRA based couplers, enabling the synthesis of arbitrary radiation field profile by Floquet- Bloch analysis of individual diffracting elements while substantially alleviating computational load. Results are further validated by 3D FDTD simulations which confirm that the radiated field profile closely matches the target design field.
@inproceedings{hadijelhouati2019diffractive, title = {Diffractive sidewall grating coupler: towards 2D free-space optics on chip}, author = {Hadij-ElHouati, Abdelfettah and Cheben, Pavel and Ortega-Moñux, Alejandro and Wangüemert-Pérez, Juan Gonzalo and Halir, Robert and Schmid, Jens H. and Molina-Fernández, Íñigo}, booktitle = {Integrated Optics: Design, Devices, Systems, and Applications V}, publisher = {SPIE}, pages = {26}, year = {2019}, month = apr, doi = {10.1117/12.2522471}, }
Conference
Engineering sub-wavelength silicon waveguides for sensing applications in the near-infrared and mid-infrared band (Conference Presentation)

Juan Gonzalo Wangüemert-Pérez, Alejandro Sánchez-Postigo, Abdelfettah Hadij-ElHouati, and 15 more authors

In Silicon Photonics XIV, Mar 2019

Abs DOI Bib

Silicon photonics is one of the most promising candidates to achieve lab-on-a-chip systems. Making use of the evanescent-field sensing principle, it is possible to determine the presence and concentration of substances by simply measuring the variation produced by the light-matter interaction in the real part of the mode effective index (in the near-infrared band), or in its imaginary part in a specific range of wavelengths (in the mid-infrared band). Regardless of which is the operating wavelength range, it is essential to select the proper sensing waveguide in order to maximize the device sensitivity. In this work we will review the potential of diffractionless subwavelength grating waveguides (SWG) for sensing applications by demonstrating their powerful capability to engineer the spatial distribution of the mode profile, and thereby to maximize the light-matter interaction. Among other things, we will demonstrate that the SWG waveguide dimensions used until now in the near-infrared are not optimal for sensing applications. In the mid-infrared band, due to the unacceptable losses of silicon dioxide for wavelengths longer than 4 μm, an additional effort is required to provide a more convenient platform for the development of future applications. In this regard, we will also show our recent progress in the development of a new platform, the suspended silicon waveguide with subwavelength metamaterial cladding. A complete set of elemental building blocks capable of covering the full transparency window of silicon (λ < ∼8.5 μm) will be discussed.
@inproceedings{wanguemertperez2019engineering, title = {Engineering sub-wavelength silicon waveguides for sensing applications in the near-infrared and mid-infrared band (Conference Presentation)}, author = {Wangüemert-Pérez, Juan Gonzalo and Sánchez-Postigo, Alejandro and Hadij-ElHouati, Abdelfettah and Leuermann, Jonas and Pérez-Armenta, Carlos and El Mokhtari Mimun, Faysal and Pereira-Martín, Daniel and Luque-González, José Manuel and Ortega-Moñux, Alejandro and Halir, Robert and Molina-Fernández, Iñigo and Cheben, Pavel and Schmid, Jens H. and Xu, Dan-Xia and Ctyroký, Jirí and Soler-Penades, Jordi and Nedeljkovic, Milos and Mashanovich, Goran Z.}, booktitle = {Silicon Photonics XIV}, publisher = {SPIE}, pages = {6}, year = {2019}, month = mar, doi = {10.1117/12.2508749}, }
[INVITED] Subwavelength structures for silicon photonics biosensing

J. Gonzalo Wangüemert-Pérez, Abdelfettah Hadij-ElHouati, Alejandro Sánchez-Postigo, and 6 more authors

Optics & Laser Technology, Jan 2019

Abs DOI Bib

Silicon photonic biosensors hold the potential for highly accurate, yet low cost point-of-care devices. Maximizing the sensitivity of the sensing chips while reducing the complexity and cost of the read-out system is pivotal to realize this potential. Here we present an extensive analysis, both from a practical and a theoretical perspective, of current biosensors, and analyze how subwavelength structures can be exploited to enhance their sensitivity. This study is not restricted just to the near-infrared band as we also determine the sensing capabilities of the suspended silicon waveguides with subwavelength metamaterial cladding working in the mid-infrared range. These waveguides have been recently proposed to cover the full transparency window of silicon (λ<∼8.5 μm), where the fingerprint spectral region of many molecules takes place and so a plethora of evanescent field absorption-based applications will be developed in the near future.
@article{wanguemertperez2019invited, title = {[INVITED] Subwavelength structures for silicon photonics biosensing}, author = {Wangüemert-Pérez, J. Gonzalo and Hadij-ElHouati, Abdelfettah and Sánchez-Postigo, Alejandro and Leuermann, Jonas and Xu, Dan-Xia and Cheben, Pavel and Ortega-Moñux, Alejandro and Halir, Robert and Molina-Fernández, Íñigo}, journal = {Optics \& Laser Technology}, publisher = {Elsevier BV}, volume = {109}, pages = {437-448}, year = {2019}, month = jan, doi = {10.1016/j.optlastec.2018.07.071}, }