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Subwavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the material properties and the propagation of light, allowing the realization of devices with unprecedented performance. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size, that restrict the available design space or compromise compatibility with high-volume fabrication technologies. Indeed, most successful SWG realizations so far relied on electron-beam lithographic techniques, compromising the scalability of the approach. Here, we report the experimental demonstration of an SWG metamaterial engineered beam splitter fabricated with deep-ultraviolet immersion lithography in a 300-mm silicon-on-insulator technology. The metamaterial beam splitter exhibits high performance over a measured bandwidth exceeding 186 nm centered at 1550 nm. These results open a new route for the development of scalable silicon photonic circuits exploiting flexible metamaterial engineering.

This Special Issue is associated with the European Conference on Integrated Optics (ECIO). The ECIO 2020 conference was held on June 23–24, 2020, and was initially scheduled in Paris, France. Due to the health and safety concerns related to the Covid-19 pandemic, the conference organizing committee has decided to adopt a digital conference format. The particularity of ECIO 2020 was to only have live talks in order to favor at maximum the interactions between speakers and attendees. This conference, organized by the Center for Nanoscience and Nanotechnology, Paris-Saclay University—CNRS, was the 22nd in a series that started in London in 1981. It attracted 640 participants from all over the world, with 103 oral presentations, including 2 plenary talks, 5 keynotes, 14 invited, 45 regular, and 57 poster speakers. The conference covered a diverse range of subjects in integrated optics and optoelectronics.

4 pags., 5 figs., Integrated microspectrometers implemented in silicon photonic chips have gathered a great interest for diverse applications such as biological analysis, environmental monitoring, and remote sensing. These applications often demand high spectral resolution, broad operational bandwidth, and large optical throughput. Spatial heterodyne Fourier-transform (SHFT) spectrometers have been proposed to overcome the limited optical throughput of dispersive and speckle-based on-chip spectrometers. However, state-of-the-art SHFT spectrometers in near-infrared achieve large optical throughput only within a narrow operational bandwidth. Here we demonstrate for the first time, to the best of our knowledge, a broadband silicon nitride SHFT spectrometer with the largest light collecting multiaperture input (320 × 410 µm) ever implemented in an SHFT on-chip spectrometer. The device was fabricated using 248 nm deep-ultraviolet lithography, exhibiting over 13 dB of optical throughput improvement compared to a single-aperture device. The measured resolution varies between 29 and 49 pm within the 1260-1600 nm wavelength range., Spanish Ministry of Science and Innovation (MICINN) (RED2018-102768-T, RTI2018-097957-B-C33, TEC2015-71127-C2-1-R (FPI Scholarship BES-2016-077798)); Community of Madrid-FEDER funds (S2018/NMT-4326); Horizon 2020 Research and Innovation Program (Marie Sklodowska-Curie 734331); H2020 European Research Council (ERC POPSTAR 647342); European Commission (H2020- ICT-26127-2017 COSMICC 688516); French Industry Ministry (Nano2022 project under IPCEI program); Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041

The high scale manufacturing capability and low cost brought by the Si platform due to its CMOS compatibility makes it now a well-established standard. However, the design of nonlinear structures with Si compatible materials is hindered by strong two photon absorption at telecom optical wavelengths in silicon [1] . Alternatives such as silicon nitride (SiN) do not show as strong nonlinearities and can be limited in terms of performances. In order to boost SiN waveguides, one can turn to the emerging field of nonlinear two-dimensional (2D) materials [2] . The idea is to integrate to the structure a highly nonlinear material. Due to the overlap between the transverse propagating mode and the thin layer crystal, the electromagnetic wave can take advantage of the high nonlinear response of the 2D material. Thus, it increases the effective nonlinearities of the waveguide structure.

On-chip avalanche photodetectors (APDs) are attractive for a sensitive detection of high-speed data light signals with low intensities. Silicon-germanium (Si-Ge) APDs are leading candidates to build reliable short-reach optical links. Appeal for Si-Ge APDs stems from larger (lower) gain-bandwidth (excess noise) at reduced voltages, CMOS-compliant production, and monolithic integration compared to their III-V alternatives [1] - [5] . Typically, Si-Ge APDs are metal-semiconductor-metal (MSM) [3] , separate absorption charge multiplication (SACM) [4] , or p-i-n [5] devices - each of them having their own advantages and drawbacks [1] . Although many Si-Ge APDs have appealing performances on their own, they are usually operated with other electronic components such as amplification stages, impeding low power consumption and low-cost detection on Si chips.

Recently, two-dimensional materials have attracted significant interests for nonlinear optics [1] . Here, we report on the experimental investigation and the numerical modelling of nonlinear pulse propagation in a heterogeneous silicon nitride channel waveguide with the integration of a few-layer WS 2 flake significantly increasing the effective nonlinearity.

International audience; Sub-wavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the propagation of light. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size. Here, we present a new nanophotonic waveguide grating concept that exploits phase-matching engineering to suppress diffraction effects for a period three times larger than those with SWG approaches. This long-period grating not only facilitates fabrication, but also enables a new diffraction-less regime with additional degrees of freedom to control light propagation. More specifically, the proposed phase-matching engineering enables selective diffraction suppression, providing new tools to shape propagation in the grating. We harness this flexible diffraction control to yield single-mode propagation in, otherwise, highly multimode waveguides, and to implement Bragg filters that combine highly-diffractive and diffraction-less regions to dramatically increase light rejection. Capitalizing on this new concept, we experimentally demonstrate a Si membrane Bragg filter with record rejection value exceeding 60 dB. These results demonstrate the potential of the proposed long-period grating for the engineering of diffraction in nanophotonic waveguides and pave the way for the development of a new generation of high-performance Si photonics devices. Silicon photonics is widely recognized as an enabling technology for next generation optical interconnects, holding the promise of providing ultra-compact and low power consumption opto-electronic transceivers, fabricated at large volumes leveraging existing CMOS facilities 1. Driven by the impressive technological development over the recent years, silicon photonics is expanding its frontiers towards new applications beyond datacom 2. These include, among others, chemical and biological sensing 3 , radio-over-fiber 4 , spectroscopy 5 , and quantum cryptography 6. In this very diverse ecosystem, combining demanding optical interconnects with disruptive new applications , sub-wavelength grating (SWG) engineering has gained momentum due to its unmatched flexibility in controlling the propagation of light in nanophotonic devices 7,8. SWG metamaterial waveguides rely on periodic silicon patterning, with a structural period shorter than half the wavelength, to synthesize refractive index and chromatic dispersion that can, in principle, be engineered at will 9,10. Unlike photonic crystals that rely on resonant light confinement 11 , SWG waveguides operate well below the bandgap, guiding light by (synthetic) refractive index difference. This way, they provide flexible control over modal confinement, birefringence and dispersion, non-achievable in conventional waveguide arrangements, alongside with low propagation loss and remarkably wide spectral bandwidth 9,10,12,13. These key advantages allowed the demonstration of several SWG-based devices

We present our latest advances in the development of compact photodetectors based on p-i-n silicon-germanium-silicon hetero-structures. We demonstrate credible high-speed performances, showing that those devices are likely to become key building blocks in next-generation photonic interconnects.

Silicon photonics has been largely developed as a platform to address the future challenges in several applications including datacom, sensing or optical communications, among others. However, the properties of silicon itself is not enough to overcome all limitations in terms of speed, power consumption and scalability. New strategies have then been encouraged based on the hybrid integration of new materials in the silicon photonics platform. In this paper, we will introduce the recent advances in the hybrid integration of doped crystalline-oxides on silicon and silicon nitride waveguides. Especially, Yttria-stabilized zirconia (YSZ) with a lattice parameter compatible with the silicon lattice has been considered because it exhibits promising linear and nonlinear optical properties: low propagation loss, no two photon absorption (TPA) due to its large bandgap energy, a large transparency window from the ultraviolet to the mid-infrared and a good Kerr effect. Furthermore, YSZ can be doped with many dopants to develop active photonic devices with strong second- and third-order nonlinearities and light emission. We have recently demonstrated propagation loss in YSZ waveguides as low as 2dB/cm at a wavelength of 1380 nm, a nonlinear refractive index (Kerr effect) comparable with the SiN coefficient and light amplification in Er3+ doped YSZ on SiN waveguides. The recent results are very promising to pave the way for the development of low cost and low power consumption devices.

The large mode size mismatch between standard single-mode optical fibers and silicon-on-insulator (SOI) waveguides poses a significant challenge to efficiently couple light from the optical fiber to the chip, and vice versa. Surface grating couplers are often used for this purpose, however, their operational bandwidth is limited to a few tens of nanometers, as a consequence of the wavelength-dependent radiation angle. This constraint seriously hampers the use of surface grating couplers for next-generation passive optical networks (PONs), in which the wavelengths used for the upstream and downstream channels are separated more than 150 nm. In this work, we present a dual-band grating coupler for 10 Gbit symmetric PONs. Our device operates as a wavelength multiplexer/demultiplexer, simultaneously coupling and combining/splitting two optical signals at the wavelengths of λ_1=1270 nm and λ_2=1577 nm. The coupler is based on engineering a surface grating coupler to obtain opposite radiation angles for the two respective wavelengths. To achieve a higher coupling efficiency, the material platform thicknesses were optimized as a tradeoff between the waveguide propagation loss and the substrate reflectivity. By judiciously choosing the period (Λ=500 nm) and the duty cycle (DC=55%) of the grating section, an efficient dual-band grating coupler is designed with a minimum feature size of 225 nm. The coupler was fabricated in ST Crolles using their 300 mm SOI platform and 193-nm deep-ultraviolet lithography, demonstrating that large-scale fabrication is feasible. Measured fiber-chip coupling efficiencies were -4.9 dB and -5.2 dB with a 3-dB bandwidth of >27 nm and 56 nm at λ_1=1270 nm and λ_2=1577 nm, respectively.

Integrated silicon nanophotonics has progressed a lot over past decades with great promises for many surging applications in optoelectronics, information and communication technologies, sensing or health monitoring. Enabling low-cost, dense integration, and compatibility with modern semiconductor nanofabrication processes, silicon nanophotonics deliver compact and high-performance devices on single chips. A variety of nanophotonic functionalities, both passive and active, are nowadays available on semiconductor substrates, leveraging the maturity of open-access silicon foundries and epitaxial germanium integration. It encompasses essential functions such as light generation and amplification, fast electro-optical modulation, and reliable conversion of optical into electrical signals. Germaniumbased optical photodetectors are main building blocks within the library of integrated silicon nanophotonics, with performances that are nowadays on par with their III-V-based counterparts. Germanium photodetectors integrated at the end of waveguides are attractive for next-generation on-chip interconnections, because of their compactness, bandwidth and speed, energy consumption and cost. In this work, we present our latest advances on silicon-germanium p-i-n waveguide-integrated photodetectors based on lateral silicon-germanium-silicon heterojunctions. Our hetero-structured photodetectors were fabricated on top of 200-mm silicon-on-insulator substrates using industrial-scale fabrication processes compatible with complementary metal-oxide-semiconductor technology. Silicon-germanium p-i-n photodetectors operated under low bias voltages exhibited low dark-currents (~100 nA), cut-off frequencies beyond 50 GHz, and photo-responsivities of about 1.2 A/W. Photodetector sensitivities of -14 dBm and -11 dBm were achieved for communication data rates of 10 Gbps and 25 Gbps, respectively. P-i-n photodetectors with lateral heterojunction operated in an avalanche regime offered an additional degree of freedom to improve device performances. High-speed and low-noise characteristics were obtained in our p-i-n photodetectors upon avalanche operation, with a gain-bandwidth product of 210 GHz and a low carrier impact ionization ratio of about 0.25. The measured sensitivity of avalancheoperated devices was -11 dBm for 40 Gbps signal detection. As demonstrated in the reported achievements, heterostructured p-i-n photodetectors are thus suitable communication devices in future intra-data center links or high-speed optical interconnects.

4 pags., 5 figs., Silicon photonics on-chip spectrometers are finding important applications in medical diagnostics, pollution monitoring, and astrophysics. Spatial heterodyne Fourier transform spectrometers (SHFTSs) provide a particularly interesting architecture with a powerful passive error correction capability and high spectral resolution. Despite having an intrinsically large optical throughput (étendue, also referred to as Jacquinot’s advantage), state-of-the-art silicon SHFTSs have not exploited this advantage yet. Here, we propose and experimentally demonstrate for the first time, to the best of our knowledge, an SHFTS implementing a wide-area light collection system simultaneously feeding an array of 16 interferometers, with an input aperture as large as 90 µm × 60 µm formed by a two-way-fed grating coupler. We experimentally demonstrate 85 pm spectral resolution, 600 pm bandwidth, and 13 dB étendue increase, compared with a device with a conventional grating coupler input. The SHFTS was fabricated using 193 nm deep-UV optical lithography and integrates a large-size input aperture with an interferometer array and monolithic Ge photodetectors, in a 4.5 mm footprint., French Industry Ministry (Nano2022) Project under IPCEI Program; Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09- 0041); Spanish Ministry of Science, Innovation and Universities (MICINN) (RTI2018-097957-B-C33, TEC2015-71127-C2-1-R FPI scholarship BES2016-077798, RED2018-102768-T); Comunidad de Madrid - FEDER funds (S2018/NMT-4326); Horizon 2020 Framework Programme for Research and Innovation under Marie Sklodowska-Curie (734331).

Efficient and reliable on-chip optical amplifiers and light sources can enable versatile integration of various active functionalities on the silicon platform. Here, we discuss our recent results of ultra-high on-chip optical gain in erbium-based hybrid waveguides with a monolithic, CMOS-compatible and scalable atomic-layer deposition process. The unique layer-by-layer nature of atomic-layer deposition enables atomic scale engineering of the gain layer properties and straightforward integration with silicon integrated waveguides. We have demonstrated up to >20 dB/cm net modal gain per unit length, the highest performance achieved from erbium-based planar waveguides integrated on silicon. Our results show significant advances towards efficient on-chip amplification, opening a route to large-scale integration of various active functionalities on silicon.

4 pags., 5 figs., 1 tab., Surface grating couplers are fundamental building blocks for coupling the light between optical fibers and integrated photonic devices. However, the operational bandwidth of conventional grating couplers is intrinsically limited by their wavelength-dependent radiation angle. The few dual-band grating couplers that have been experimentally demonstrated exhibit low coupling efficiencies and rely on complex fabrication processes. Here we demonstrate for the first time, to the best of our knowledge, the realization of an efficient dual-band grating coupler fabricated using 193 nm deep-ultraviolet lithography for 10 Gbit symmetric passive optical networks. The footprint of the device is 17 × 10 µm. We measured coupling efficiencies of −4.9 and −5.2 dB with a 3-dB bandwidth of 27 and 56 nm at the wavelengths of 1270 and 1577 nm, corresponding to the upstream and downstream channels, respectively., Spanish Ministry of Science, Innovation and Universities (MICINN) (RTI2018-097957-B-C33, TEC2015-71127-C2-1-R with FPI Scholarship BES-2016-077798); Community of Madrid - FEDER funds (S2018/NMT-4326); Horizon 2020 Research and Innovation Program (Marie Sklodowska-Curie 734331); H2020 European Research Council (ERC POPSTAR 647342); European Commission (H2020- ICT-26127-2017 COSMICC 688516); French Industry Ministry (Nano2022 project under IPCEI program); Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041).

Optical photodetectors are at the forefront of photonic research since the rise of integrated optics. Photodetectors are fundamental building blocks for chip-scale optoelectronics, enabling conversion of light into an electrical signal. Such devices play a key role in many surging applications from communication and computation to sensing, biomedicine and health monitoring, to name a few. However, chip integration of optical photodetectors with improved performances is an on-going challenge for mainstream optical communications at near-infrared wavelengths. Here, we present recent advances in heterostructured silicon-germanium-silicon p-i-n photodetectors, enabling high-speed detection on a foundry-compatible monolithic platform.

Integrated silicon nanophotonics has rapidly established itself as intriguing research field, whose outlets impact numerous facets of daily life. Indeed, nanophotonics has propelled many advances in optoelectronics, information and communication technologies, sensing and energy, to name a few. Silicon nanophotonics aims to deliver compact and high-performance components based on semiconductor chips leveraging mature fabrication routines already developed within the modern microelectronics. However, the silicon indirect bandgap, the centrosymmetric nature of its lattice and its wide transparency window across optical telecommunication wavebands hamper the realization of essential functionalities, including efficient light generation/amplification, fast electro-optical modulation, and reliable photodetection. Germanium, a well-established complement material in silicon chip industry, has a quasi-direct energy band structure in this wavelength domain. Germanium and its alloys are thus the most suitable candidates for active functions, i.e. bringing them to close to the silicon family of nanophotonic devices. Along with recent advances in silicon–germanium-based lasers and modulators, short-wave-infrared receivers are also key photonic chip elements to tackle cost, speed and energy consumption challenges of exponentially growing data traffics within next-generation systems and networks. Herein, we provide a detailed overview on the latest development in nanophotonic receivers based on silicon and germanium, including material processing, integration and diversity of device designs and arrangements. Our Review also emphasizes surging applications in optoelectronics and communications and concludes with challenges and perspectives potentially encountered in the foreseeable future.

Nonlinear optics has not stopped evolving, offering opportunities to develop novel functionalities in photonics. Supercontinuum generation, a nonlinear optical phenomenon responsible for extreme spectral broadening, attracts the interest of researchers due to its high potential in many applications, including sensing, imaging, or optical communications. In particular, with the emergence of silicon photonics, integrated supercontinuum sources in silicon platforms have seen tremendous progress during the past decades. This article aims at giving an overview of supercontinuum generation in three main silicon-compatible photonics platforms, namely, silicon, silicon germanium, and silicon nitride, as well as the essential theoretical elements to understand this fascinating phenomenon.

A two-octave spanning supercontinuum generation in the O-band communication window on an integrated silicon nitride platform is reported. The nitrogen-rich silicon nitride waveguides were fabricated through low temperature processes on an industrial platform (

openaire: EC/H2020/820423/EU// | openaire: EC/H2020/834742/EU//ATOP Compact silicon integrated lasers are of significant interest for various applications. We present a detailed investigation for realizing sub-mm long on-chip laser structures operating at λ = 1.533 µm on the silicon-on-insulator photonic platform by combining a multi-segment silicon waveguide structure and a recently demonstrated erbium-doped thin film deposition technology. Quarter-wave shifted distributed feedback structures (QWS-DFB) are designed and a detailed calculation of the lasing threshold conditions is quantitatively estimated and discussed. The results indicate that the requirements for efficient lasing can be obtained in various combinations of the designed waveguide DFB structures. Overall, the study proposes a path to the realization of compact (< 500 µm) on-chip lasers operating in the C-band through the hybrid integration of erbium-doped aluminum oxide processed by atomic layer deposition in the silicon photonic platform and operating under optical pumping powers of few mW at 1,470 nm.

Brillouin optomechanics has recently emerged as a promising tool to implement new functionalities in silicon photonics, including high-performance opto-RF processing and nonreciprocal light propagation. One key challenge in this field is to maximize the photon–phonon interaction and the phonon lifetime, simultaneously. Here, we propose a new, to the best of our knowledge, strategy that exploits subwavelength engineering of the photonic and phononic modes in silicon membrane waveguides to maximize the Brillouin gain. By properly designing the dimensions of the subwavelength periodic structuration, we tightly confine near-infrared photons and GHz phonons, minimizing leakage losses and maximizing the Brillouin coupling. Our theoretical analysis predicts a high mechanical quality factor of up to 700 and a remarkable Brillouin gain yielding 3500 ( W ⋅ m ) − 1 for minimum feature size of 50 nm, compatible with electron-beam lithography. We believe that the proposed waveguide with subwavelength nanostructure holds great potential for the engineering of Brillouin optomechanical interactions in silicon.

Point-defect nanocavities based on silicon planar photonic crystal (PhC) have been optimized and studied for sensing the refractive index of gases in the mid-infrared wavelength region. The point-defect has been introduced at the center of the triangular lattice of the photonic crystal that is made up of circular air holes, making it suitable for probing the properties of the gas found within the cavity. By optimizing the radius and position of the air holes closest to the defect region precisely, on the order of a few nanometers, the ratio of the quality factor to mode volume (Q/V) for the point-defect PhC nanocavities can be increased considerably. Moreover, a perturbation method has been implemented in order to study the resonant wavelength shift of the optimized point-defect nanocavity modes caused by a small change in the refractive index of the gas. The results obtained show that sensitivity of 270 nm/RIU (Refractive Index Unit) and a detection limit of $$10^{-4}$$ RIU can be achieved for the optimized point-defect PhC nanocavities. These nanocavities have been designed to oscillate at a single mode with a high Q/V thus enabling to sense the refractive index of gases with high sensitivity.

The Si transparency (1.1 μm – 8 μm wavelength) contains the strongest absorption features of a wide range of chemical and biological substances. However, the use of SOI in the mid-IR is hampered by the large absorption of the buried oxide (BOX) for wavelengths above 4 μm. Silicon membranes have garnered great interest for their unique capability to overcome the BOX limitation while leveraging the advantages of Si photonics. On the other hand, silicon is uniquely poised for the implementation of wideband mid-IR sources based on nonlinear frequency generation. Promising supercontinuum and frequency comb generation have already been demonstrated in Si. Still, current implementations have a limited flexibility in the engineering of phase-matching conditions and dispersion, which complicates the shaping of the nonlinear spectrum. Patterning Si with features smaller than half of the wavelength (well within the capabilities of standard large-volume fabrication processes) has proven to be a simple and powerful tool to implement metamaterials with optimally engineered properties. Here, we present the design of nanostructured silicon membrane waveguides with ultra-wideband flat anomalous dispersion in a wavelength span exceeding 5 µm. Our three-dimensional finite difference time domain (FDTD) calculations predict flat anomalous dispersion near 50 ps/km⋅nm between 2.5 µm and 8 µm wavelength. These results illustrate the potential of subwavelength metamaterial engineering to control chromatic dispersion in Si membrane waveguides. This is a promising step towards the implementation of wideband nonlinear sources in the mid-IR for silicon photonics.

The impact of Pt or Co as alloying elements for Ni-based metallization of GeSn layers has been investigated. As far as the solid-state reaction is concerned, the overall phase sequence is the same for all metallizations: at low temperature, a Ni-rich phase is obtained; it is then consumed to form the low resistivity mono-stanogermanide phase. Nevertheless, the addition of an alloying element has an impact on Ni consumption, Ni-rich and mono-stanogermanide phases’ formation temperatures. Moreover, the addition of Co or Pt positively impacts Sn segregation by delaying this phenomenon. Co has a weak influence on morphological and electrical properties. On the other hand, Pt improves the surface morphology by delaying the Ni(GeSn) phase agglomeration and enhancing the process window in which the sheet resistance remains low.

International audience; The strong evolution of silicon photonics towards very low power consumption circuits leads to the development of new strategies for photonic devices, especially for power-hungry components such as optical modulators. One strategy is to use Pockels effect in Si waveguides. However, bulk Si is a centrosymmetric semiconductor, which cannot exhibit any second order optical nonlinearities. Nonetheless, under a strain gradient, generated by depositing a stressed layer on Si waveguides, this restriction vanishes. In our work, we experimentally demonstrated a Pockels effect based electro-optic modulation at high frequency (> 5GHz) using a strained silicon Mach-Zehnder modulator.

Silicon nanophotonics represents a scalable route to deploy complex optical integrated circuits for multifold applications, markets, and end-users. Most recently, applications such as optical communications and interconnects, sensing, as well as quantum-based technologies, among others, present additional opportunities for integrated silicon nanophotonics to expand its frontiers from laboratories to industrial product development. Within a wide set of functionalities that silicon nanophotonic chips can afford, the availability of low-loss optical input/output interfaces has been regarded as a major practical obstacle that hampers long-term success of integrated photonic platforms. Indeed, fiber-chip interfaces based on diffraction gratings are an attractive solution to resonantly couple the light between planar waveguide circuits and standard single-mode optical fibers. Surface grating couplers provide much more alignment tolerance in fiber attach compared with most conventional edge-coupled alternatives, while retaining the much-needed control of the fiber placement on the chip surface and wafer-level-test capability that the in-plane convertors lack. Here, we report on our recent advances in the development of high-performance fiber-chip grating couplers that exploit the blazing effect. This is achieved with well-established dual-etch processing in interleaved teeth-trench arrangements or using L-shaped grating-teeth-profile geometries. The first demonstration of the L-shaped-based grating coupler yielded a coupling loss of -2.7 dB, seamlessly fabricated into a 300-mm foundry manufacturing process using 193-nm deep-ultraviolet stepper lithography. Moreover, silicon metamaterial L-shaped fiber couplers may promote robust sub-decibel coupling of light, reaching a simulated coupling loss of -0.25 dB, while featuring device layouts (>120 nm) compatible with lithographic technologies in silicon semiconductor foundries., SPIE OPTO 2020 - Smart Photonic and Optoelectronic Integrated Circuits XXII, February 3-6, 2020, San Francisco, California, Series: Proceedings of SPIE

Nonlinear all-optical technology is an ultimate route for the next-generation ultrafast signal processing of optical communication systems. New nonlinear functionalities need to be implemented in photonics, and complex oxides are considered as promising candidates due to their wide panel of attributes. In this context, yttria-stabilized zirconia (YSZ) stands out, thanks to its ability to be epitaxially grown on silicon, adapting the lattice for the crystalline oxide family of materials. We report, for the first time to the best of our knowledge, a detailed theoretical and experimental study about the third-order nonlinear susceptibility in crystalline YSZ. Via self-phase modulation-induced broadening and considering the in-plane orientation of YSZ, we experimentally obtained an effective Kerr coefficient of n ^ 2 YSZ = 4.0 ± 2 × 10 − 19 m 2 · W − 1 in an 8% (mole fraction) YSZ waveguide. In agreement with the theoretically predicted n ^ 2 YSZ = 1.3 × 10 − 19 m 2 · W − 1 , the third-order nonlinear coefficient of YSZ is comparable with the one of silicon nitride, which is already being used in nonlinear optics. These promising results are a new step toward the implementation of functional oxides for nonlinear optical applications.

We report on the first demonstration of high-speed optical modulation exploiting Pockels effect in strained silicon waveguides. Bandwidths larger than 20 GHz and low insertion loss have been achieved at a wavelength of 1550 nm.

On-chip optical amplifiers operating at telecom wavelengths are crucial elements for signal recovering and routing in photonic integrated circuits. In this work, we present the optical and structural properties of Er-doped yttria-stabilized zirconia (YSZ) thin films for the implementation of on-chip optical amplifiers in hybrid multifunctional photonic platforms. Photoluminescence excitation measurements have revealed strong luminescence at 1530 nm under 960 nm wavelength pumping, with lifetime values around 2 ms and a strong Er3++–Er3+ interaction for Er3+ doping concentrations beyond 1.5 atomic percentage (at%). This work contributes to establish the solid foundations for a class of Er-doped on-chip amplifiers using the robust and stable YSZ host matrix.

4 pags., 4 figs., 1 tab., Silicon nitride (SiN) waveguides provide a substantially lower index contrast, thermo-optic coefficient, and reduced birefringence compared to silicon-on-insulator waveguides. These properties make SiN a prominent candidate for implementation of ultra-wideband dual-polarization photonics circuits with a great potential for datacom applications. State-of-the-art SiN power splitters are still hampered in terms of either bandwidth or single-polarization operation. Here, we propose to overcome these limitations by exploiting modal and waveguide symmetry engineering in a single-mode slot waveguide. This topology prevents mode-beating, while granting symmetric power splitting for both polarizations. Experimental characterization of the fabricated device shows low loss (, Spanish Ministry of Science, Innovation and Universities (MICINN) (IJCI-2016-30484, RTI2018- 097957-B-C33, TEC2015-71127-C2-1-R with FPI scholarship BES-2016-077798); Comunidad de Madrid - FEDER funds (S2018/NMT-4326); Horizon 2020 Framework Programme (Marie Sklodowska-Curie 734331); H2020 European Research Council (ERC POPSTAR 647342); European Commission (H2020-ICT-26127-2017 COSMICC 688516); French Industry Ministry (Nano2022 project under IPCEI program); Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041).

International audience; We report supercontinuum generation in nitrogen-rich (N-rich) silicon nitride waveguides fabricated through back-end complementary-metal-oxide-semiconductor (CMOS)-compatible processes on a 300 mm platform. By pumping in the anomalous dispersion regime at a wavelength of 1200 nm, two-octave spanning spectra covering the visible and near-infrared ranges, including the O band, were obtained. Numerical calculations showed that the nonlinear index of N-rich silicon nitride is within the same order of magnitude as that of stoichiometric silicon nitride, despite the lower silicon content. N-rich silicon nitride then appears to be a promising candidate for nonlinear devices compatible with back-end CMOS processes.

Integrated wavelength filters with high optical rejection are key components in several silicon photonics circuits, including quantum photon-pair sources and spectrometers. Non-coherent cascading of modal-engineered Bragg filters allows for remarkable optical rejections in structures that only support transverse-electric (TE) polarized modes such as uncladded 220-nm-thick silicon. However, the restriction to TE-only platforms limits the versatility of the non-coherent cascading approach. Here, we propose and experimentally demonstrate a new, to the best of our knowledge, approach for high-rejection filters in polarization-diverse platforms by combining non-coherent cascading of modal-engineered Bragg filters and anisotropy-engineered metamaterial bends. Bragg filters provide a high rejection of the TE mode, while the metamaterial bends remove any residual power propagating in the transverse-magnetic (TM) mode, without any penalty in terms of insertion loss or device footprint. Based on this strategy, we demonstrate optical rejection exceeding 60 dB in 300-nm-thick, cladded silicon waveguides.

A method for generating Fano resonance in a standalone silicon nanobeam cavity is reported and investigated thoroughly. The proposed approach eliminates the inconvenience from the unexpected side-c...

Silicon photonics, considered as a major photonic platform for optical communications in data centers, is today also developed for others applications including quantum photonics and sensing. Advanced silicon functionalities based on optical nonlinearities are then required. As the presence of inversion symmetry in the Si crystal structure prevents the exploitation of second-order optical nonlinearities, the generation of strain gradients in Si by a stressed material can be considered. However, due to the semiconductor nature of silicon with the presence of carriers, no clear evidence of second-order nonlinearities have been reported yet. Here we report an experimental demonstration of high-speed Pockels effect in silicon waveguides at 1550 nm. Additionally, a theoretical model is developed to describe its frequency behavior. A second-order nonlinear susceptibility $$\chi _{xxy}^{(2)}$$ χ x x y ( 2 ) of −1.8 ± 0.2 pm V−1 is then experimentally determined. These results pave the way for the development of fast linear electro-optic effect for advanced silicon photonics devices.

International audience; Photoniques 93 L e silicium (Si) est l'un des ma-tériaux qui ont radicalement changé le monde scientifique, technologique et sociétal à partir de l'invention du transistor en 1947. L'extraordinaire évolution vers la miniaturisation des transistors et l'augmentation de leur nombre pour la réalisation de circuits intégrés et fonctions complexes ont conduit au développement de l'industrie de la mi-croélectronique et de ses multiples applications résultantes. Cette évolution a principalement suivi la « loi de Moore », énoncée par Gordon Moore en 1965, prévoyant une augmentation exponen-tielle du nombre de transistors par puce tous les 18 mois. Depuis cette époque, le silicium est le matériau le plus utilisé de l'industrie des semi-conducteurs pour des raisons physiques et technologiques (qualité de son oxyde, la silice, et de l'in-terface avec son oxyde, propriétés méca-niques et thermiques) et économiques (large accès à la matière première, le si-licium ; retour sur investissement des infrastructures rapidement atteint). Cependant, depuis quelques années, les progrès fulgurants de l'électro-nique silicium atteignent des limites, en particulier en termes de puissance consommée bien trop élevée dans une ère où l'impact énergétique est une prio-rité majeure, et de bande passante pour laquelle les débits visés pour répondre à la demande croissante devient trop faible. En effet, les nombreuses inter-connexions électriques nécessaires aux transferts de données au sein des puces électroniques sont une source majeure de dissipation de puissance. Pour pallier ces limitations, les interconnexions optiques, consistant à miniaturiser des liens optiques complets en vue de vé-hiculer des signaux rapides sur puce, sont considérées depuis une vingtaine d'années comme une solution alternative intéressante au tout-électronique. Afin de conserver la compatibilité avec les technologies de la microélec-tronique (essentiellement CMOS), l'utilisation du silicium pour la pho-tonique a rapidement été considérée comme la voie principale à explorer, laissant de côté des solutions telles que l'intégration totalement hybride de composants optoélectroniques à base de semiconducteurs III/V déjà dé-veloppées pour le domaine des télécoms par fibres optiques. L'évolution vers la photonique Si a été notamment per-mise grâce à l'émergence de substrats polyvalents en silicium sur isolant (SOI) et aux propriétés optiques intéressantes du silicium offrant une large fenêtre de transparence pour des longueurs d'onde allant de 1,1 μm à 7 μm [2]. En outre, les substrats SOI donnent accès à un fort contraste d'indice de réfraction entre celui du silicium Si (n Si ≈ 3,47 vers λ = 1,55 μm) et celui de la silice SiO 2 (n SiO2 ≈ 1,45), permettant le développe-ment de composants compacts adap-tés à une forte densité d'intégration des composants optiques. En dépit de ces atouts, le silicium présente plusieurs inconvénients in-trinsèques pour la photonique, à sa-voir principalement une structure de bandes électroniques indirecte et une maille cristalline centrosymétrique. Ces propriétés conduisent à une très faible efficacité du processus d'émission de photons (pour la réalisation de sources), et à l'absence d'effet électro-optique li-néaire (Pockels) couramment exploité dans les systèmes de communications modernes avec le niobate de lithium ou les matériaux semiconducteurs III/V pour la réalisation de modulateurs élec-tro-optiques rapides. Si l'on y ajoute sa transparence dans le proche infrarouge, empêchant la réalisation de photodé-tecteurs dans cette gamme de lon-gueurs d'onde, il est ainsi notable que le silicium en lui-même ne présente que peu de propriétés favorables à la réali-sation des trois fonctions essentielles : source/modulation/détection d'un lien optique intégré. Malgré tout, les efforts de recherche des centres académiques et industriels déployés pour étendre CIRCUITS INTÉGRÉS photoniques silicium La photonique silicium suit la devise : « plus petit, moins cher, plus rapide », comme la microélectronique plusieurs années auparavant, en exploitant une intégration à très grande échelle des composants et circuits intégrés de plus en plus complexes. L'incroyable évolution des systèmes communicants avec en particulier le déploiement des réseaux Internet et mobiles, des objets connectés et des capteurs a fait émerger la photonique silicium pour répondre à ces nouveaux enjeux majeurs. article publié sous les conditions définies par la licence Creative Commons attribution License CC-BY (http://creativecommons.org/licenses/by/4.0), qui autorise sans restrictions l'utilisation, la diffusion, et la reproduction sur quelque support que ce soit, sous réserve de citation correcte de la publication originale.

Slotted photonic crystal waveguides (SPCWs) were designed to act as refractive index sensing devices at mid-infrared (IR) wavelengths around λ = 3.6 μm. In particular, effort was made to engineer the input and output slot waveguide interfaces in order to increase the effective sensitivity through resonant tapering. A slotted PhC waveguide immersed in air and liquid cladding layers was considered. To determine the performance of the sensor, the sensitivity of the device was estimated by calculating the shift in the upper band edge of the output transmission spectrum. The results showed that the sensitivity of a conventionally designed SPCW followed by modifications in the structure parameter yielded a 510 nm shift in the wavelength position of the upper band edge, indicating a sensitivity of more than 1150 nm per refractive index unit (RIU) with an insertion loss level of −0.3 dB. This work demonstrates the viability of photonic crystal waveguide high sensitivity devices in the Mid-IR, following a transposition of the concepts inherited from the telecom band and an optimization of the design, in particular a minimization of photonic device insertion losses.

We present the design and analysis of a high efficiency slotted photonic crystal waveguide for gas sensing applications in the mid-infrared wavelength range. We designed the slotted photonic crysta...

We propose the realization of an on-chip dual identical narrowband Bragg filter at ∼ 1310 and ∼ 1950 n m wavelengths simultaneously based on the silicon-on-insulator (SOI) platform. By taking advantage of subwavelength corrugation behavior at large wavelengths and the difference in the mode areas of the involved modes at the two widely separated wavelengths, undesired diffraction losses are circumvented while achieving Bragg resonances at the two wavelengths simultaneously. A double-corrugation Bragg grating rib waveguide filter is proposed, with two sets of gratings, the inner one close to the rib operating near 1310 nm wavelength, with the outer grating being designed to achieve a transmission dip around 1950 nm. Introducing a proper lateral misalignment to the set of inner grating indents, a dual identical narrowband Bragg filter with ∼ 0.47 n m 3 dB bandwidth at ∼ 1310 n m and ∼ 1950 n m is achieved. The proposed design strategy based on the SOI platform relies on a single-etching fabrication process and presents potential applications in situations where equal-bandwidth filtering is needed in on-chip communications and sensing.

Slotted photonic crystal (SPC) cavities provide strong evanescent fields, high quality factors, and small mode volumes. Hence, SPC cavities have been identified as promising candidates for the implementation of high-performance sensors and the development of hybrid devices combining silicon with other active materials. Nevertheless, most state-of-the-art demonstrations rely on electron beam lithography and operate in the telecommunications band near the 1550 nm wavelength. Here, we report the experimental demonstration of SPC cavities operating in the datacom O-band, near 1340 nm wavelength, fabricated using deep-ultraviolet (DUV) lithography. The O-band provides very interesting properties for sensing, communications, and hybrid integration: namely, lower optical absorption of water, lower dispersion in standard optical fibers, and the emission of active materials like carbon nanotubes. On the other hand, DUV fabrication opens interesting opportunities for large volume production. The proposed cavities exhibit a high quality factor exceeding 20,000 and a small mode volume of 0.023 ( λ / n ) 3 . These results open interesting perspectives to exploit enhanced light–matter interaction in SPC cavities harnessing industrial-like fabrication processes.

A double corrugation quarterly wavelength shifted (QWS) distributed feedback (DFB) Bragg grating cavity which includes two sets of Bragg gratings located at different positions away from a waveguide center is proposed. It can support two wavelength-far-separated resonances, for instance 735 nm and 1310 nm as an illustrative example of the proposed flexible approach applied to a silicon nitride rib waveguide. Based on the proposed design principle, the two sets of Bragg distributed corrugations operate nearly independently, diffraction losses being minimized by design principle even though these two resonances are widely separated. The proposed approach of a double corrugation cavity that relies on a single-etching fabrication process, fits with the need of situations where two simultaneous widely spaced resonances are required, with potential for applications to on-chip amplification, lasing, second harmonic generation, and nonlinear optical process in hybrid integrated waveguides.

Silicon photonic devices need to be complemented with other materials for the realization of optically active devices. The unique emission properties of single-walled carbon nanotubes are especially promising for efficient light emitters realization in the telecommunication wavelength ranges and for their integration in silicon photonic devices. However one of the problem of carbon nanotubes is their low quantum efficiency. One of the approach to address this problem is to couple the carbon nanotube emission with micro-resonators in order to the enhance their radiative emission. Here we report on the fabrication and optical characterization of a silicon micro-slot-ring resonator coupled with selected single walled semiconducting carbon nanotubes for high photoluminescence emission in the O band telecommunication wavelength. Hyperspectral photoluminescence maps show spectra with sharp resonances superimposed to the nanotube emission bands which demonstrate the coupling of the nanotubes with the evanescent tails in air of the electric field localized in the photonic modes of the micro-resonator. The enhancement of the photoluminescence is achieved over three different CNTs chirality for more than 30 sharp resonances in a single microring resonator. This work paves the way for the development of integrated light sources based on carbon nanotubes in silicon photonic devices.