Nonlinear applications in the mid-infrared regime based on germanium on silicon platform

This abstract reviews our progress in characterizing nonlinear properties of low loss germanium-on-silicon waveguides in the mid-infrared wavelength. All-optical modulation is demonstrated in these waveguides and indicates the suitability of this platform for nonlinear applications in this long wavelength regime

Suspended silicon integrated platform for the long-wavelength mid-infrared band

The atmospheric-transmission window and the fingerprint region of many substances overlaps with the long-wave infrared band. This has enabled the emergence of a new path for photonic integrated circuits, which could exploit the potential applications of this wavelength range, including chemical and bio sensing. In this work we review our latest advances in the suspended silicon platform with subwavelength grating lateral cladding at 7.7-µm wavelength. Suspended waveguides only require one lithographic etch step and can be specifically designed to maximize sensitivity when used as sensors. Waveguides with propagation loss of 3.1±0.3 dB/cm are demonstrated, as well as bends with less than 0.1 dB/bend. Suspended waveguides based on shifted Bragg grating lateral cladding are also reported, with propagation loss of 5.1±0.6 dB/cm. These results prepare the ground for the development of a platform capable of covering the entire mid-infrared band. Keywords: suspended silicon, mid-infrared, long-wave infrared, subwavelength grating, Bragg.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

High performance silicon photonic devices based on practical metamaterials

Robert Halir, et al., "High performance silicon photonic devices based on practical metamaterials," OECC/PSC, 7-12 July 2019, Fukuoka (Japan)Subwavelength grating metamaterials are enabling a new generation of high-performance silicon photonic devices. Here we discuss the fundamental physics along with some of the latest advances in this rapidly expanding field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Ministerio de Economía y Competitividad, Programa Estatal de Investigación Orientada a los Retos de la Sociedad (cofinanciado FEDER) – TEC2016-80718-R, TEC2015-71127-C2-1-R (FPI BES-2016-077798) and IJCI-2016-30484; Community of Madrid – S2018/NMT-4326, Marie Sklodowska-Curie –734331, Czech Science Foundation – 1900062

Silicon high performance devices using subwavelength structures

Ministerio de Economía y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad (cofinanciado FEDER), Proyecto TEC2016-80718-R Universidad de MälagaSilicon 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.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Subwavelength-grating metamaterial integrated devices for the near- and mid-infrared wavelengths

The subwavelength patterning of planar structures is now widely used in silicon photonics, enabling the synthesis of metamaterials with engineered optical properties, including refractive index, dispersion, and anisotropy. A wide range of integrated devices based on subwavelength grating (SWG) metamaterials have been demonstrated at telecom wavelengths, some with unprecedented performance. The benefits of SWG metamaterials can be leveraged not only in the typical telecom near-infrared bands, but also at the longer mid-infrared wavelengths. In this invited presentation, we will review our latest developments in SWG-based silicon and germanium photonic devices for the near- and the mid-infrared.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Subwavelength-engineered metamaterial devices for integrated photonics

The engineering of subwavelength grating metamaterials has become an essential design strategy in silicon photonics. The lithographic segmentation of integrated waveguides at the subwavelength scale enables the synthesis of on-chip metamaterials and provides control over optical properties such as mode delocalization, wavelength dispersion, and anisotropy. At the near-infrared wavelengths of the 1.55-μm telecom band, a range of subwavelength-based devices with unprecedented performance has been demonstrated, including couplers, filters, and polarization-handling structures. In this invited paper, we review the foundations of anisotropic subwavelength grating metamaterials and discuss our latest advances in five new subwavelength-enhanced devices: a millimeter-long optical antenna that is evanescently coupled to diffractive lateral segments, thereby achieving a record far-field beam width of 0.1º in silicon; a multi-line integrated Bragg filter also using lateral loading segments, which produces 20 non-uniformly spaced spectral notches with a 3-dB linewidth as low as 210 pm; a low-loss curved wavelength demultiplexer; a segmented multi-mode interference coupler based on novel bricked subwavelength gratings, yielding a 1-dB bandwidth exceeding 140 nm; and a suspended waveguide platform with low propagation loss at mid-infrared wavelengths.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Building high-performance integrated optical devices using subwavelength grating metamaterials

Ministerio de Ciencia, Innovación y Universidades (MCIU) (PID2019-106747RB-I00), Consejería de Economía, Conocimiento, Empresas y Universidad (CECEU) (UMA18-FEDERJA-219, P18-RT-1453, P18-RT-793) and National Research Council of Canada (NRC) Collaborative Science, Technology and Innovation Program (CSTIP) (HTSN 209).The use of subwavelength grating structures in silicon waveguides have fuelled the development of integrated optical components with superior performance. By a judicious lithographic pattern 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.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Group IV mid-infrared devices for sensing

Group IV photonics is a topical research field, with potential applications in diverse areas such as bio-chemical and environmental sensing, security, communications, healthcare and astronomy. Many of these applications require accessing longer wavelengths in what is called the mid-infrared (MIR) region and specifically in the "fingerprint" region, as it contains strong fundamental vibrational transitions of most molecules. The transparency range of the traditional material platform used for years in near-infrared (NIR) silicon photonics (silicon-on-insulator) is not suitable due to its limited wavelength transparency range, therefore new materials need to be explored.In this project SOI has been used to produce a slot waveguide at 3.8m, a wavelength range in which SiO2 absorption begins to be significant, but with a careful design and a proper selection of a suitable platform (i.e. thicker Si and SiO2 layers), low loss devices can still be produced, as it has been demonstrated extensively. A slot was chosen since it is a waveguide design highly suitable for sensing. The slot waveguide had a propagation loss of 1.4dB/cm and high field confinement in the slot gap. A new platform of suspended silicon with sub-wavelength lateral cladding has also been demonstrated, allowing the use of SOI for the full transparency range of Si. This platform has significant advantages compared to other, suspended solutions, in that a single etch step is required to fabricate the suspended waveguides and the resulting devices are more robust since the suspended region for a comparable device is much thinner, allowing the design of wider devices. This has been demonstrated with the design, fabrication and characterization of waveguides, bends, multimode interferomenters (MMI) and a Mach-Zehnder interferometer (MZI). The waveguides fabricated with this technique achieved a loss as low as 0.82dB/cm.The Ge-on-Si platform has also been developed with the demonstration of waveguides and MMIs with propagation loss as low as 0.58dB/cm at 3.8m for the former and 0.21dB insertion loss for the latter. Waveguides and MMIs have also been fabricated and characterized in the wavelength range between 7.5m and 9.5m with a minimum loss of 2.5dB/cm, extending the range at which this material has been characterized. Unforeseen losses in Ge have been discovered in this wavelength range, a discussion of the possible sources is included in this thesis. Evanescent field sensing of Thiodiglycol has also been demonstrated, showing a good agreement with a commercial FTIR in the aforementioned range

Germanium for photonic applications

Localized GOI wires have been grown using a LPE process resulting in single crystal layers up to 400 µm in length and 5 µm in width. We have reported on the design, fabrication and characterisation of a 4-channel AMMI structure integrated with germanium p-i-n photodetectors to form a silicon photonics receiver. Light detection at 50 Gb/s has been demonstrated with a low dark current of < 20 nA at -1 V bias. The AMMI structure exhibits a low insertion loss of < -0.5 dB and cross-talk of < -15 dB across the 4 channels

Low-loss mid-infrared SOI slot waveguides

Mid-infrared sensing is a field that has recently attracted attention due to the potential to reach the fingerprint region for several chemical compounds, allowing enhanced sensitivity. To further enhance the sensitivity of photonic sensors slot waveguides can be used as waveguides as the electric field amplitude can be greatly increased in the gap region. In this letter, we present silicon on insulator slot waveguides with a 1.4 ± 0.2 dB/cm propagation loss at 3.8 µm wavelength, as well as strip to slot transitions with a loss of 0.09 ± 0.01 dB/transition and slot bends with a loss of 0.18 dB/bend