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Integration of nanomaterials within optical nanocavities provides a unique potential for flexible control of light emitters properties by photonic band gap engineering and cavity Purcell effects. Here, we propose a one-dimensional heterostructure nanocavity exhibiting both non-coupled and coupled cavity modes, i.e. simultaneously acting as a single cavity and as a photonic molecule. The main cavity resonances are engineered to yield a wide spectral separation and for the first time to match the emission wavelengths of two different kinds of semiconducting single wall carbon nanotubes (s-SWNTs). By probing the photoluminescence (PL) from s-SWNTs coupled with the nano cavity modes, coupling of the s-SWNTs PL simultaneously into the several cavity modes is demonstrated. For modes governed by the photonic molecule behavior, the wavelength splitting of the two coupled modes is dominated by the cavity barrier width. The excitation of the bonding (B) and anti-bonding (AB) cavity modes then yields PL resonant enhancement that can be tuned by the pumping position and polarization filter. These results demonstrate the potential of the proposed multimode photonic molecule to tailor light-nanomaterial interactions on chip, paving the way for the development of tunable hybrid photonic circuits relying on nanoemitters in cavities for light generation purposes.

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

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.

A 1342nm EML with an external SOA has enabled the 20km, 50Gb/s downstream link for ITU-T, 50G-PON to be demonstrated for the first time. Using a 25G-class receiver and real-time equalisation, an OMA sensitivity of −24dBm and a link budget of 35.6dB were measured.

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).

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 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.

A novel silicon beam splitter based on modal and symmetry engineering in slot waveguides is reported. We experimentally demonstrate insertion loss and imbalance below 1 dB over a broad bandwidth of 390 nm, for both TE and TM polarizations., 2019 IEEE 16th International Conference on Group IV Photonics (GFP), August 28-30, 2019, Singapore, Singapore

New optical materials for hybrid photonic integration on silicon platform have become a hot research topic aiming at providing additional functionalities. In this regard, functional oxides are a very interesting class of materials due to their singular properties. Material engineering is commonly employed to tune and manipulate such properties at will, thus being functional oxides often used to build active reconfigurable elements in complex systems. Transparent oxides with moderate refractive indexes are targeted for hybrid integration due to the rewarding benefits envisioned. Yttria-Stabilized Zirconia (YSZ) is a chemically stable oxide1 with a transparency range that spans from the visible to the mid-IR2, with a refractive index around 2.1, which makes this functional oxide interesting for the development of low-loss waveguides when grown over a low contrast substrate. While these optical properties are very interesting for various applications, including on-chip optical communications and sensing, YSZ has remained almost unexplored in photonics up to now. Nevertheless, this complex functional oxide shows interesting optical properties such as low-moderate propagation losses of 2 dB/cm at telecom wavelengths3. In our work, we explore the deposition of erbium doped YSZ by pulsed layer deposition (PLD) on a multilayer approach providing outstanding luminescence in correspondence with C-band of telecommunication window (λ=1530 nm) and in the visible range by means of up-conversion processes. The optical properties of active layers of Er-doped YSZ grown on waveguides in different platforms and under resonant pumping will be discussed in this paper, as well as their propagation losses. Based on the preliminary study of these active hybrid systems, we envision light amplification functionalities based on rare-earth doped functional oxides.

9 pags., 6 figs., 1 tab., High-performance optical beam splitters are of fundamental importance for the development of advanced silicon photonics integrated circuits. However, due to the high refractive index contrast of silicon-on-insulator platforms, state-of-the-art nanophotonic splitters are hampered by trade-offs in bandwidth, polarization dependence and sensitivity to fabrication errors. Here, we present a new strategy that exploits modal engineering in slotted waveguides to overcome these limitations, enabling ultra-broadband polarization-insensitive optical power splitters with relaxed fabrication tolerances. The proposed splitter design relies on a single-mode slot waveguide that is gradually transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate −3 ± 0.5 dB polarization-independent transmission for an unprecedented 390 nm bandwidth (1260–1650 nm), even in the presence of waveguide width deviations as large as ±25 nm., This work has been funded in part by the Spanish Ministry of Science, Innovation and Universities under grants TEC2015-71127-C2-1-R (FPI scholarship BES-2016-077798) and IJCI-2016-30484; and the Community of Madrid (S2013/MIT-2790). This project has received funding from the EMPIR program (JRP-i22 14IND13 Photind), co-financed by the participating countries and the European Union’s Horizon 2020 research and innovation program; and from the Horizon 2020 research and innovation program under the Marie Sklodowska- Curie Grant No. 734331. This work has been partially funded by the Agence National pour la Recherche, Project MIRSPEC (ANR-17-CE09-0041) and the H2020 European Research Council (ERC) (ERC POPSTAR 647342). The sample fabrication has been performed at the Plateforme de Micro-Nano-Technologie/C2N, which is partially funded by the “Conseil Général de l’Éssonne”. This work was partly supported by the French RENATECH network.

Bragg filters stand as a key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we present a new generation of high-performance Bragg filters that exploit subwavelength and corrugation symmetry engineering to overcome bandwidth-rejection trade-off in state-of-the-art implementations. We experimentally show flexible control over the width and depth of the Bragg resonance, unlocking new tools for the implementation of notch filters with arbitrary bandwidth and rejection level. These results pave the way for the implementation of high-performance on-chip wavelength filters with a great potential for nonlinear-based applications, e.g. next generation Si-based photon-pair sources for quantum photonic circuits.

Semiconducting single walled carbon nanotubes (s-SWNT) have an immense potential for the development of active optoelectronic functionalities in ultra-compact hybrid photonic circuits. Specifically, s-SWNT have been identified as a very promising solution to implement light sources and detectors in the silicon photonics platform. Here we present our most recent results on the hybrid integration of s-SWNT with silicon resonators, including micro-rings, micro-disks and photonic crystal cavities. We show chirality-wise resonant enhancement of s-SWNT emission, allowing on-chip selection of (8,6) or (8,7) SWNT chiralities present in a high-purity polymer-sorted solution. We also demonstrate that, opposite to the common knowledge, the longitudinal component in transverse-magnetic optical modes can efficiently interact with drop-casted s-SWNTs arranged along the chip surface. The proposed hybrid integration approach unlocks new tools to optimize light-SWNT interaction in silicon photonic circuits and open a new route towards single-chirality selection in hybrid Si-SWNT devices, even if the SWNT solution contains various chiralities. Hence, these results stand as an important step towards the implementation of s-SWNT-based devices for the silicon photonics platform.

International audience; Wideband and polarization-independent wavelength filters with low sensitivity to temperature variations have great potential for wavelength division multiplexing applications. However, simultaneously achieving these metrics is challenging for silicon-on-insulator photonics technology. Here, we harness the reduced index contrast and the low thermo-optic coefficient of silicon nitride to demonstrate waveguide Bragg grating filters with wideband apolar rejection and low thermal sensitivity. Filter birefringence is reduced by judicious design of a triangularly shaped lateral corrugation. Based on this approach, we demonstrate silicon nitride Bragg filters with a measured polarization-independent 40 dB optical rejection with negligible off-band excess loss, and a sensitivity to thermal variations below 20 pm/°C.

Silicon photonics has emerged as a very promising technology platform for the implementation of high-performance, low-cost, ultra-compact circuits that can monolithically cointegrate electronic, opto-electronic and optic functionalities. However, Si neither has efficient light emission or detection in the telecom wavelength range, nor exhibits efficient electro-optic Pockels effect, hindering the implementation of integrated active devices like sources, detectors, or modulators. Current approaches relay on different materials to provide active functionalities in Si photonics, resulting in highly complex integration schemes that compromise cost-effectiveness. Semiconducting single-wall carbon nanotubes (SWNTs) are capable of emitting and detecting near-infrared light at room temperature and exhibit intrinsically fast electro-optic effects. They have also proven promising uses in micro-electronic devices, making them an ideal material to provide active functionalities in the Si photonic platform. In this work, we propose and experimentally validate the possible use of slot photonic waveguides to improve interaction between SWNTs and Si waveguide modes. Fabricated Si slot micro-ring shown an experimental similar to 60% photo-luminescence improvement compared to previous demonstration based on Si strip waveguide resonators. These results prove the potential of Si slot waveguides for the implementation of efficient SWNT-based Si photonic devices.

openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOP Recently, erbium-doped integrated waveguide devices have been extensively studied as a CMOS-compatible and stable solution for optical amplification and lasing on the silicon photonic platform. However, erbium-doped waveguide technology still remains relatively immature when it comes to the production of competitive building blocks for the silicon photonics industry. Therefore, further progress is critical in this field to answer the industry's demand for infrared active materials that are not only CMOS-compatible and efficient, but also inexpensive and scalable in terms of large volume production. In this work, we present a novel and simple fabrication method to form cost-effective erbium-doped waveguide amplifiers on silicon. With a single and straightforward active layer deposition, we convert passive silicon nitride strip waveguide channels on a fully industrial 300 mm photonic platform into active waveguide amplifiers. We show net optical gain over sub-cm long waveguide channels that also include gratingcouplers and mode transition tapers, ultimately demonstrating tremendous progress in developing cost-effective active building blocks on the silicon photonic platform. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Silicon photonics is considered an enabling technology for next generation datacom applications, providing ultra-compact and high-bandwidth transceivers that are cost-effectively fabricated at the existing CMOS facilities. Among photonic devices developed in silicon, Bragg gratings are routinely used for the realization of key functionalities including wavelength filtering, dispersion engineering and sensing. However, the realization of Bragg filters that simultaneously provides narrowband operation and high rejection remains a challenge in the Si platform. Indeed, the small core size of Si wires, together with the high index contrast between the silicon and the oxide cladding results in a strong interaction of the optical mode with the Bragg structure. Several approaches have been proposed to implement narrowband Bragg filters in Si wires including ultra-small corrugations (a few nanometres), periodic claddings, sub-wavelength engineering or inter-mode coupling. Nevertheless, these filters typically have comparatively weak light rejection performance due to fabrication errors limiting the accurate control of the grating geometry over few millimeter-long waveguide structures. In this work, we present a novel waveguide Bragg grating geometry that leverages the large index contrast between Si and air in membrane waveguides to overcome these limitations, yielding both narrow bandwidth and high rejection ratio. We use a novel waveguide corrugation geometry that radiates out the higher order modes, allowing effective single-mode operation for micrometric fully etched membrane waveguides. The high mode confinement of these waveguides results in weak interaction with the sidewall corrugation, thus narrowband operation is achieved. On the other hand, the high rejection ratio is achieved by combining reflection and radiation effects within the Bragg resonance. Based on this concept, we designed and experimentally demonstrated notch filters in single-etch suspended Si waveguides with cross-sections as large as 0.5 µm (height) by 1.1 µm (width). We show a narrow bandwidth of 4 nm for a 500 nm wide corrugation, with a high rejection ratio exceeding 50 dB for a filter length of only 700 µm

Research of integrated light sources into the silicon platform has been extremely active for the past decades. Solutions such as the integration of III / V materials and components on silicon have been developed in a context of pre-industrial research, devices and systems intending very close to the market applications. The germanium(-tin) route has also demonstrated remarkable breakthroughs. The rationales of this research are the realization of optical interconnects. In parallel with these approaches, another interesting research field is the integration of nano-emitters, with the perspective of the realization of classical light sources but also of single photon and photon pair sources, in particular for quantum-on-chip communications. In this context, we propose the use of carbon nanotubes (CNTs) for the integration into silicon photonics towards novel optoelectronic devices. Indeed, CNTs are nanomaterials of particular interest in photonics thanks to their fundamental optical properties including near-IR luminescence, Stark effect, Kerr effect and absorption. Here, we report on the study of the light emission coupling from CNTs into optical nanobeam cavities implemented on the SOI platform. A wide range of situations have been studied by varying the deposition conditions of CNT-doped PFO polymer layers but also by considering different possible geometries of nanobeam cavities. Under optical pumping, we observe a very efficient coupling of the photoluminescence of the nanotubes with the modes of the nanocavities as well as a spectral narrowing of the photoluminescence spectra as a function of the optical power of the pump. These results contribute to the future realization of CNTs lasers, single photon and photon pair sources integrated on silicon. The authors thank the support of the European Commission's FP7-Cartoon project.

International audience; Wideband polarization beam splitters (PBS) are a key building block in polarization management circuits for wavelength division multiplexing applications. A broadband PBS on a 300-mm silicon nitride (SiN) photonic platform is reported based on phase-controlled directional coupler (DC). Unlike classical DC-based PBS made on silicon, the proposed configuration leverages the comparatively lower birefringence in SiN to yield wideband and efficient splitting. A semi-analytical approach, based on transfer matrix modeling and 3-D finite difference time domain, has been used to design and optimize the structure for O-band operation. The proposed PBS has been experimentally demonstrated showing insertion loss (IL) lower than 0.6 dB and extinction ratio (ER) as high as 10 dB over 95-nm bandwidth for both polarizations. Furthermore, this simplified architecture eases cascading, allowing the demonstration of IL below 1.1 dB and ER larger than 24 dB over 85-nm wavelength range in a dual-stage configuration.

Semiconducting single wall carbon nanotubes (s-SWCNTs) are promising room-temperature telecom-band nano-emitters that could be integrated in silicon photonic circuits for the realization of on-chip optical sources. We report here the integration of a large quantity of s-SWCNTs as an active cladding layer on top of silicon micro/nano cavities. The gathered results show that the luminescence of the SCNTs can be efficiently coupled into the considered photonic crystal cavity modes, which exhibits a clear spectral narrowing as a function of the pump power. These results constitute an important step towards the realization of a carbon nanotube optical source integrated into the silicon platform.

International audience; Functional and easy-to-integrate nanodevices operating in the telecom wavelength ranges are highly desirable. Indeed, the pursuit for faster, cheaper, and smaller transceivers for datacom applications is fueling the interest in alternative materials to develop the next generation of photonic devices. In this context, single wall carbon nanotubes (SWNTs) have demonstrated outstanding electrical and optical properties that make them an ideal material for the realization of ultracompact optoelectronic devices. Still, the mixture in chirality of as-synthesized SWNTs and the necessity of precise positioning of SWNT-based devices hinder the development of practical devices. Here, the realization of operational devices obtained using liquid solution-based techniques is reported, which allow high-purity sorting and localized deposition of aligned semiconducting SWNTs (s-SWNTs). More specifically, devices are demonstrated by combining a polymer assisted extraction method, which enables a very effective selection of s-SWNTs with a diameter of about 1–1.2 nm, with dielectrophoresis, which localizes the deposition onto silicon wafers in aligned arrays in-between prepat-terned electrodes. Thus, long semiconducting nanotubes directly contact the electrodes and, when asymmetric contacts (i.e., source and drain made of different metals) are used, each device can operate both as photoemitter and as photodetector in the telecom band around 1.55 µm in air at room temperature.

We present a novel suspended Si waveguide approach for hybrid near-infrared and mid-infrared operation. Large waveguide cross-sections allow mid-infrared propagation, while an original corrugation yields effective single-mode near-infrared operation. Exploiting this concept, we demonstrated Bragg filters with 4 nm bandwidth and 40 dB rejection.

We report on the integration of carbon nanotubes in silicon micro-cavities to develop cost-effective light sources. Strong light coupling from carbon nanotubes was demonstrated into silicon photonics resonators, nanobeam cavities and photonic crystals.

International audience; This conference talk will sum up our recent contributions related to the integration of semiconductor carbon nanotubes (s-SWNTs) as an active material in silicon photonics. This work is motivated by the possible use of s-SWNTs for light emission, detection, and modulation relying on the same hybrid on-silicon integration platform. We will first describe experimental results carried out to prepare high quality thin polymer layers doped with purified s-SWNTs. Our efforts to integrate this effective active material in silicon photonic resonators and nanocavities will be then described. We report cavity enhanced near infrared emission from nanotubes accompanied with a spectral narrowing effect when increasing pumping power levels and a threshold-like behavior regarding device light emission.

The large transparency window of silicon (1.1 - 8 μm wavelength range) makes it a promising material for the implementation of on-chip sensors operating over an ultra-wide wavelength range. However, the implementation of the silicon-on-insulator platform is restricted by the absorption of buried oxide layer for wavelengths above 4 μm. Here, we report our advances in development of silicon waveguides for broadband operation extending from near- to mid-infrared wavelengths. We present suspended silicon waveguides that exploit a novel periodic corrugation approach to circumvent the buried oxide absorption problem and provide effective single mode operation simultaneously for near- and mid-infrared wavelengths.

We report our advances in development of subwavelength engineered silicon photonic devices for near- and mid-infrared applications. By periodically patterning Si with a pitch small enough to suppress diffraction, we synthesize an effective photonic medium with refractive index between those of Si and the cladding material. This technique releases new degrees of freedom in engineering of light-matter interaction, chromatic dispersion and light propagation in Si photonic waveguides. We present an overview of our recent results in the realization of novel devices including filters and waveguides for near- and mid-infrared wavelength range.

A six-port-based frequency discriminator for phase noise measurement is proposed. This circuit makes use of a delay line discriminator configuration, thus not requiring reference oscillator. Furthermore, the use of a six-port network allows an extremely simple and completely passive solution well suited for low power oscillator measurement. A detailed study of the architecture is performed including the system noise sources. Besides, a prototype of the proposed six-port based delay line frequency discriminator is evaluated. Phase noise measurements of a commercial RF VCO are performed and compared with the results obtained with commercial metrology equipment with good agreement.

A frequency locked loop (FLL) for phase noise reduction of wideband voltage controlled oscillators is proposed. The key building block of the system is a low noise (−160 dBV/Hz) and high sensitivity (22 V/GHz) delay line frequency discriminator with 5–8 GHz coverage, which makes use of a high performance multilayer hybrid. The authors derive closed-form, universal design equations for the maximum noise reduction and stability of the FLL circuitry. Application of the proposed technique to a state-of-the-art voltage controlled oscillator operating in the 5–8 GHz band yields a phase noise reduction of 8–10 dB at 100 kHz and 5 dB at 1 MHz off the carrier, which shows the results are in good agreement with the simulated results; so phase noise better than −107 dBc/Hz at 100 kHz and better than −123.5 dBc/Hz at 1 MHz is obtained.

International audience; Optical interconnects are expected to overcome the copper link bottlenecks. Amongthe different developed technologies, silicon photonics becomes one of the preferred solutions. Indeed,due to its compatibility with the CMOS platform, silicon photonics is considered as aviable solution for the development of the future generation photonic interconnects. However,the on-chip integration of all photonic and optoelectronic building blocks (sources, modulatorsand detectors. . . ) on the silicon platform is very complex and is not cost-effective due to thevarious materials used: Ge for detection, Si for waveguiding and modulators and III-V for lasing.We propose here to use carbon nanotubes (CNTs) integrated into silicon photonics for the developmentof all optoelectronic devices. Indeed, CNTs are nanomaterials of particular interest inphotonics thanks to their fundamental optical properties including near-IR luminescence, Starkeffect, Kerr effect and absorption. In consequence, CNTs have the ability to emit, modulateand detect light in the wavelength range of the silicon transparency. Furthermore, they are alsoconsidered as an electronic compatible material thanks to the recent advances in nanoelectronicsbased on CNTs.Here, we report on the study of the light emission coupling from CNTs into optical resonatorsimplemented on the silicon-on-insulator (SOI) platform including ring resonators, nano-beamcavities, micro-disks. . . . A theoretical and experimental analysis of the light interaction of CNTswith micro-ring resonators based on slot waveguides and slot photonic crystal heterostructurecavities will be presented.

Polarization management is a key functionality in many photonic applications including telecommunications, polarization diversity circuits and sensing, to name a few. Developing integrated circuits capable of reliably controlling polarization state would result in compact and low cost circuits with improved stability, compared with fiber or bulk optics solutions. Polarization rotators are a key building block of these circuits. Unfortunately, stringent fabrication tolerances make the integration of polarization rotators highly challenging. The main limitation arises from the need to tightly control the profile of the hybrid modes in the rotator waveguide as well as their relative phase shift during propagation. Both values are very sensitive to waveguide geometry variations, seriously hindering their practical application. We have developed a technology independent scheme that enables fabrication error compensation, substantially relaxing device tolerances. In our scheme, three polarization rotation waveguides are interconnected with two tunable phase shifters to correct geometry deviations. Interestingly, these phase shifters also enable dynamic wavelength tuning and output polarization extinction ratio selection. We also showed that, by adding an output phase shifter, we can control the relative phase. Hence, we can yield any desired output state of polarization. We have implemented this scheme in the silicon-on-insulator platform using simple waveguide heaters as tunable phase shifters. We experimentally demonstrated an unprecedented polarization extinction range of 40 dB (±20 dB). Furthermore, the device showed a 98% coverage of the Poincaré sphere with a tunability range covering the complete C-band. These results prove the potential of our scheme to alleviate the, otherwise, very stringent fabrication tolerances, overcoming the major limitation of current integrated polarization managing devices., 2016 Progress in Electromagnetic Research Symposium (PIERS), August 8-11, 2016, Shanghai, China

Subwavelength gratings (SWG) are photonic structures with a period small enough to suppress diffraction, thereby acting as artificial dielectric materials, also called all-dielectric metamaterials. This property has been exploited in many high-performance photonic integrated devices in the silicon-on-insulator (SOI) platform. While SWG waveguides are theoretically lossless, they may exhibit leakage penalty to the substrate due to a combination of reduced modal confinement and finite thickness of the buried oxide (BOX) layer. In this Letter, for the first time, to the best of our knowledge, we analyze substrate leakage losses in SWG waveguides. We establish a direct relation between the effective index of the waveguide mode and the leakage losses which, remarkably, is independent of the geometric parameters of the SWG waveguide. This universal relation is demonstrated both numerically and experimentally, and it provides practical design guidelines to mitigate leakage losses. For BOX thicknesses of 2 and 3 μm, we find negligible leakage losses when the mode effective index is higher than 1.65 and 1.55, respectively.

Demanding applications such as video streaming, social networking, or web search relay on a large network of data centres, interconnected through optical links. The ever-growing data rates and power consumption inside these data centres are pushing copper links close to their fundamental limits. Optical interconnects are being extensively studied with the purpose of solving these limitations. Among the different possible technology platforms, silicon photonics, due to its compatibility with the CMOS platform, has become one of the preferred solutions for the development of the future generation photonic interconnects. However, the on-chip integration of all photonic and optoelectronic building blocks (sources, modulators and detectors…) is very complex and is not cost-effective due to the various materials involved (Ge for detection, doped Si for modulators and III-V for lasing). Carbon nanotubes (CNTs) are nanomaterials of great interest in photonics thanks to their fundamental optical properties, including near-IR room-temperature foto- and electro- luminescence, Stark effect, Kerr effect and absorption. In consequence, CNTs have the ability to emit, modulate and detect light in the telecommunications wavelength range. Furthermore, they are being extensively developed for new nano-electronics applications. In this work, we propose to use CNTs as active material integrated into silicon photonics for the development of all optoelectronic devices. Here, we report on the development of new integration schemes to couple the light emission from CNTs into optical resonators implemented on the silicon-on-insulator and silicon-nitride-on-insulator platforms. A theoretical and experimental analysis of the light interaction of CNTs with micro-ring resonators based on strip and slot waveguides and slot photonic crystal heterostructure cavities were carried out.

Polarization management is a key functionality in many photonic applications, including optical communications, imaging or quantum information. Developing integrated devices capable of reliably controlling polarization state would result in compact and low cost circuits with improved stability compared with fiber or bulk optics solutions. However, stringent fabrication tolerances make the integration of polarization managing elements highly challenging. The main challenge in polarization controllers, composed by polarization rotators and polarization phase shifters, is to precisely control rotation angle in integrated polarization rotators. Proposed solutions typically require sophisticated fabrication processes or extremely tight fabrication tolerances, seriously hindering their practical application. Here we present a technology independent polarization controller scheme that relies on phase shifters to largely relax fabrication tolerances of polarization rotators. In addition, these phase shifters enable dynamic wavelength tuning. In our scheme, three polarization rotation elements are interconnected with two tunable phase shifters to adjust the polarization extinction ratio, while an output polarization phase shifter is used to select the relative phase. This way we can achieve any desired output state of polarization. We have implemented this scheme in the silicon-on-insulator platform, experimentally demonstrating a record polarization extinction range of 40 dB (± 20 dB) with a 98% coverage of the Poincare sphere. Furthermore, the device is tunable in the complete C-band. These results constitute, to the best of our knowledge, the highest polarization extinction range achieved in a fully integrated device.

International audience; Hybrid structures are needed to fully exploit the great advantages of Si photonics and several approaches have been addressed where Si devices are bonded to different materials and nanostructures. Here we study the use of semiconductor carbon nanotubes for emission in the 1300 nm wavelength range to functionalize Si photonic structures in view of optoelectronic applications. The Si micro-rings are fully characterized by near field forward resonant scattering with 100 nm resolution. We show that both TE and TM modes can be addressed on the top of the micro-rings in a vectorial imaging of the in-plane polarization components. We coupled the Si micro-resonators with selected carbon nanotubes for high photoluminescence emission. Coupling nanotubes with the evanescent tails in air of the electric field localized in the photonic modes of the micro-resonators is demonstrated by sharp resonances over imposed to the nanotube emission bands. By mapping the Si and the nanotube emission we demonstrate that strong enhancement of the nanotube photoluminescence can be achieved both in the photonic modes of micro-disks and slot micro-rings, whenever the spatial overlap between nano-emitters and photonic modes is fulfilled.

International audience; Hybrid systems based on carbon nanotubes emitting in the telecom wavelength range and Si-photonic platforms are promising candidates for developing integrated photonic circuits. Here, we consider semiconducting single walled carbon nanotubes (s-SWNTs) emitting around 1300 nm or 1550 nm wavelength. The nanotubes are deposited on quartz substrate for mapping their photoluminescence in hyperspectral near-field microscopy. This method allows for a sub-wavelength resolution in detecting the spatial distribution of the emission of single s-SWNTs at room temperature. Optical signature delocalized over several micrometers is observed, thus denoting the high quality of the produced carbon nanotubes on a wide range of tube diameters. Noteworthy, the presence of both nanotube bundles and distinct s-SWNT chiralities is uncovered.

Polarization controllers are key elements in many fields of optics, including coherent communications, optical imaging, and quantum applications. Here we present a technology-independent polarization controller scheme based on electrically tunable phase shifters and polarization rotators with largely relaxed fabrication tolerances. Using this scheme, we experimentally demonstrate a fully integrated polarization controller in the silicon-on-insulator platform that is tunable over the complete C-band and achieves a polarization extinction range of 40 dB (±20 dB ). These results constitute, to the best of our knowledge, the highest polarization extinction range achieved in a fully integrated device, and overcome the existing limitation in the trade-off between integration and performance in polarization management circuits.

International audience; Polymer-sorted semiconducting single-walled carbon nano-tubes (SWNTs) provide room-temperature emission at near-infrared wavelengths, with potential for large volume production of high-quality solutions and wafer-scale depo-sition. These features make SWNTs a very attractive material for the realization of on-chip light sources. Coupling SWNT into optical microcavities could enhance and guide their emission, while enabling spectral selection by cavity resonance engineering. This could allow the realization of bright, narrowband sources. Here, we report the first demonstration of coupling SWNTs into the resonant modes of Si hollow-core photonic crystal cavities. We exploit the strong evanescent field in these resonators to interact with SWNT emission, coupling it into an integrated access wave-guide. Based on this concept, we demonstrate narrowband SWNT emission resonantly coupled into a Si bus wave-guide with a full width at half-maximum of 0.34 nm and an off-resonance rejection exceeding 5 dB. Single-walled carbon nanotubes (SWNTs) are a versatile material with outstanding electrical [1,2] and optical properties [3,4]. Indeed, the same SWNT-based device can be reconfigured to perform as a light emitter, detector, or transistor, just by changing the applied voltage [5]. Hence, they have an immense potential to serve as an efficient connection bridge between the electrical and optical planes in future silicon optoelectronic circuits. In the optical domain, semiconducting SWNTs are a direct bandgap material exhibiting room-temperature electro-and photolumi-nescence in the visible and near-infrared [6,7]. Recent advances in solution processing [8] and wafer-scale selective deposition [9] have opened a new path toward the realization of on-chip light sources for the Si photonic platform, based on the use of SWNTs. These could become a cost-effective alternative to current solutions relying on III-V materials. However, the emission from SWNTs has a low quantum efficiency [10] and a wide spectrum that hinder their use as narrowband sources [11]. These two drawbacks could be circumvented by integrating the SWNTs into Si photonic microcavities. The resonant light confinement in small volumes in those cavities could be used to enhance light emission through the Purcell effect [12], while their high quality factors could be exploited to spectrally narrow the wideband SWNT emission. Spectral narrowing has been demonstrated for the emission of individual SWNTs coupled to suspended 1D photonic crystal microcavities [11,13]. This configuration has shown very promising results for quantum photonic applications relying on single-photon sources [14]. However, the intensity of a single emitter could not suffice for datacom or sensing applications. One possible solution to increase the emission intensity is to use a network of SWNTs [7,15–18]. Networks of high-purity polymer-sorted semiconducting SWNTs have shown room-temperature photoluminescence [7] and intrinsic gain [15]. It is worth noting that this sorting technique results in polymer wrapped semiconducting SWNTs. This precludes photo-luminescence quenching when the SWNTs are in contact with a silicon substrate, obviating the need to suspend them in air. Hence, polymer-sorted SWNTs allow cost-effective and large volume on-chip deposition based on drop casting or spin coating techniques. In this context, remarkably narrowband emission with quality factors of Q ˆ 3800 has been demonstrated for networks of polymer-sorted SWNTs in 2D silicon photonic crystal microcavities [16]. Still, no coupling between cavity-enhanced SWNT emission and on-chip waveguides has been reported for this kind of structure. Resonant enhancement of the emission from SWNT networks and coupling to Si pho-tonic waveguides has been shown for Si micro-ring resonators [19]. Nevertheless, these traveling wave resonators have comparatively large mode volumes that limit their potential for Purcell emission enhancement.

In this work we propose the utilization of the Butler matrix as a six-port I/Q demodulator. The inherent symmetry of its topology allows to overcome the intrinsic amplitude and phase imbalances of the traditional approaches making it more suitable for the design of high performance six-port networks. To demonstrate the validity of the proposal a Butler matrix has been designed covering the complete UWB band and its results are compared with the traditional approaches.

Hybrid integration of unconventional optical materials is arguably a promising way to substantially extend a range of chip functionalities on traditional silicon-based platforms. Especially, functional oxides are very promising because they exhibit many attractive properties, including superconductivity, piezoelectricity, ferroelectricity, and optical effects. In this article, we demonstrate hybrid photonic platform with an Erbium-doped (Er-doped) Yttria-Stabilized Zirconia (YSZ) thin film used as an active luminescent cladding on top of low-loss Silicon Nitride (SiN) waveguides. This active layer has been grown by a pulsed laser deposition (PLD) technique. Optical characterizations via photoluminescence (PL) measurements were performed in both normal and in-plane light incidence to demonstrate strong near-infrared (near-IR) emission of Er ions in the Er:YSZ thin film. Moreover, we also observed an intense in-plane guided PL emission in visible and near-IR wavelengths from hybrid Er:YSZ-on-SiNx waveguides. These results pave the way towards rare-earth-doped YSZ structures on silicon-based platforms, thereby affording required function versatility for future photonic integrated circuits.