arXiv subjects

Laurent Vivien

Publications and source records attributed to Laurent Vivien.

At least 37 records · Page 2Linked to original sources

arXiv2022

Spatial and polarization division multiplexing harnessing on-chip optical beam forming

On-chip spatial and polarization multiplexing have emerged as a powerful strategy to boost the bandwidth of integrated optical transceivers. State-of-the-art multiplexers require accurate control of the relative phase or the spatial distribution among different guided optical modes, seriously compromising the bandwidth and performance of the devices. To overcome this limitation, we propose a new approach based on the coupling between guided modes in integrated waveguides and optical beams free-propagating on the chip plane. The engineering of the evanescent coupling between the guided modes and free-propagating beams allows spatial and polarization multiplexing with state-of-the-art performance. To demonstrate the potential and versatility of this approach, we have developed a two-polarization multiplexed link and a three-mode multiplexed link using standard 220-nm-thick silicon-on-insulator technology. The two-polarization link shows a measured -35 dB crosstalk bandwidth of 180 nm, while the three-mode link exhibits a -20 dB crosstalk bandwidth of 195 nm. These bandwidths cover the S, C, L, and U communication bands. We used these links to demonstrate error-free transmission (bit-error-rate < 10-9) of two and three non-return-to-zero signals at 40 Gbps each, with power penalties below 0.08 dB and 1.5 dB for the two-polarization and three-mode links respectively. The approach demonstrated here for two polarizations and three modes is also applicable to future implementation of more complex multiplexing schemes.

physics.optics↗

arXiv2022

Electro-optic properties of ZrO2, HfO2 and LiNbO3 ferroelectric phases: A comprehensive and comparative study with density functional theory

We report the Pockels electro-optic properties of ZrO2 and HfO2 orthorhombic Pbc21 and rhombohedral R3m ferroelectric phases, and we compare them to the well-known LiNbO3 Pockels material from density functional theory calculations using the CRYSTAL suite of programs. Specifically, three essential processes are explicitly investigated: The electronic, the ionic (or vibrational), and the piezoelectric contributions. Our calculations reveal that the ionic part coming from the low frequency phonon modes contributes the most to the electro-optic coefficients of rhombohedral LiNbO3 and of orthorhombic ZrO2 and HfO2. While these low-frequency modes show zero contribution to Pockels coefficients for the rhombohedral phase of the latter compounds.

cond-mat.mtrl-sci↗

arXiv2022

Low-Power consumption Franz-Keldysh effect plasmonic modulator

In this paper we report on a low energy consumption CMOS-compatible plasmonic modulator based on Franz-Keldysh effect in germanium on silicon. We performed integrated electro-optical simulations in order to optimize the main characteristics of the modulator. A 3.3 $dB$ extinction ratio for a 30 $μm$ long modulator is demonstrated under 3 $V$ bias voltage at an operation wavelength of 1647 $nm$. The estimated energy consumption is as low as 20 $fJ/bit$.

physics.optics↗

arXiv2022

Broadband behavior of quadratic metalenses with a wide field of view

Metalenses are attracting a large interest for the implementation of complex optical functionalities in planar and compact devices. However, chromatic and off-axis aberrations remain standing challenges. Here, we experimentally investigate the broadband behavior of metalenses based on quadratic phase profiles. We show that these metalenses do not only guarantee an arbitrarily large field of view but are also inherently tolerant to longitudinal and transverse chromatic aberrations. As such, we demonstrate a single-layer, silicon metalens with a field of view of 86° and a bandwidth up to 140 nm operating at both 1300 nm and 1550 nm telecommunication wavelength bands.

physics.optics↗

arXiv2021

Mid-infrared Fourier-transform spectrometer based on metamaterial lateral cladding suspended silicon waveguides

Integrated mid-infrared micro-spectrometers have a great potential for applications in environmental monitoring and space exploration. Silicon-on-insulator (SOI) is a promising platform to tackle this integration challenge, due to its unique capability for large volume and low-cost production of ultra-compact photonic circuits. However, the use of SOI in the mid-infrared is restricted by the strong absorption of the buried oxide layer for wavelengths beyond 4 μm. Here, we overcome this limitation by utilizing metamaterial-cladded suspended silicon waveguides to implement a spatial heterodyne Fourier-transform (SHFT) spectrometer operating near 5.5μm wavelength. The metamaterial-cladded geometry allows removal of the buried oxide layer, yielding measured propagation loss below 2 dB/cm between 5.3μm and 5.7μm wavelengths. The SHFT spectrometer comprises 19 Mach-Zehnder interferometers with a maximum arm length imbalance of 200 μm, achieving a measured spectral resolution of 13cm-1 and a free-spectral range of 100 cm-1 near 5.5μm wavelength.

physics.optics↗

arXiv2021

Boosting the SiN nonlinear photonic platform with transition metal dichalcogenide monolayers

In the past few years, we have witnessed an increased interest in the use of 2D materials for the realization of hybrid photonic nonlinear waveguides. Although graphene has attracted most of the attention, other families of 2D materials such as transition metal dichalcogenides have also shown promising nonlinear performances. In this work, we propose a strategy for designing silicon nitride waveguide structures embedded with molybdenum disulfide for nonlinear applications. The transverse geometry of the hybrid waveguides structure is optimized for high third order nonlinear effects using optogeometrical engineering and multiple layers of molybdenum disulfide. Stacking multiple monolayers, results in an improvement of 2 orders of magnitude in comparison with standard silicon nitride waveguides. The performance of the hybrid waveguides is then investigated in terms of four wave mixing enhancement in micro ring resonator configurations. A 6,3 dB signal idler conversion efficiency is reached around 1550 nm wavelength for a 5 mW pumping level.

physics.optics↗

arXiv2021

Generating 10-GHz phonons in nanostructured silicon membrane optomechanical cavity

Flexible control of photons and phonons in silicon nanophotonic waveguides is a key feature for emerging applications in communications, sensing and quantum technologies. Strong phonon leakage towards the silica under-cladding hampers optomechanical interactions in silicon-on-insulator. This limitation has been circumvented by totally or partially removing the silica under-cladding to form pedestal or silicon membrane waveguides. Remarkable optomechanical interactions have been demonstrated in silicon using pedestal strips, membrane ribs, and photonic/phononic crystal membrane waveguides. Still, the mechanical frequencies are limited to the 1-5 GHz range. Here, we exploit the periodic nanostructuration in Si membrane gratings to shape GHz phononic modes and near-infrared photonic modes, achieving ultrahigh mechanical frequency (10 GHz) and strong photon-phonon overlap (61.5%) simultaneously. Based on this concept, we experimentally demonstrate a one-dimension optomechanical micro-resonator with a high mechanical frequency of 10 GHz and a quality factor of 1000. These results were obtained at room temperature and ambient conditions with an intracavity optical power below 1 mW, illustrating the efficient optical driving of the mechanical mode enabled by the proposed approach.

physics.optics↗

arXiv2021

Silicon-on-insulator optomechanical microresonator with tight photon and phonon confinement

The implementation of optomechanical devices in silicon-on-insulator (SOI), the canonical silicon photonics technology is seriously hampered by the strong phonon leakage into the silica under-cladding. This limitation has been partially circumvented by total or partial removal of the silica under-cladding to form Si membranes or pedestal waveguides. However, this approach complicates integration with standard silicon optoelectronics circuitry, limiting the versatility and application of the strategy. Here, we propose and demonstrate a new strategy to confine photons and phonons in SOI without removing the silica under-cladding. Inspired by end-fire antenna arrays, we implement a periodic nanostructuration of silicon that simultaneously enables cancelling phonon leakage by destructive interference and guiding of photons by metamaterial index confinement. Based on this concept, we implement SOI optomechanical micro-resonators yielding remarkable optomechanical coupling (go=49 kHz) between 0.66 GHz mechanical modes and near-infrared optical modes. The mechanical mode exhibits a measured quality factor of Qm = 730, the largest reported for SOI optomechanical resonators, without silica removal. This value compares favorably with state-of-the-art Si membrane waveguides recently used to demonstrate remarkable Brillouin interactions in silicon (Qm ~ 700). These results open a new path for developing optomechanics in SOI without the need for silica removal, allowing seamless co-integration with current Si optoelectronics circuits, with a great potential for applications in communications, sensing, metrology, and quantum technologies.

physics.optics↗

arXiv2020

Stress measurements in silicon photonics by integrated Raman spectroscopy

Complex 3D integration of photonic and electronic integrated circuits is of particular interest to carry the photonics roadmap and to address challenges but involves mechanical stress, often detrimental for the behavior of optical components. Existing experiments failed to carefully analyze the stress in such integrated optical devices due to the requirement in terms of feature sizes, few hundreds of nanometers, and 3D-stacked integration. We present for the first time the characterization of the stress tensor of a silicon waveguide using Integrated Raman Spectroscopy (IRS). This experimental technique is directly sensitive to the effective stress, which involves changes in optical properties of the guided mode, at the working wavelength and polarization state of the photonic component. The experimental stress tensor is in good agreement with simulations.

physics.app-ph↗

arXiv2020

High-quality photonic entanglement based on a silicon chip

The fruitful association of quantum and integrated photonics holds the promise to produce, manipulate, and detect quantum states of light using compact and scalable systems. Integrating all the building-blocks necessary to produce high-quality photonic entanglement in the telecom wavelength range out of a single chip remains a major challenge, mainly due to the limited performance of on-chip light rejection filters. We report a stand-alone, telecom-compliant, device that integrates, on a single substrate, a nonlinear photon-pair generator and a passive pump rejection filter. Using standard channel-grid fiber demultiplexers, we demonstrate the first entanglement quantification of such a integrated circuit, showing the highest raw quantum interference visibility for energy-time entangled photons over two telecom-wavelength bands. Genuinely pure maximally entangled states can therefore be generated thanks to the high-level of noise suppression obtained with the pump filter. These results will certainly further promote the development of more advanced and scalable photonic-integrated quantum systems compliant with telecommunication standards.

quant-ph↗

arXiv2019

Optical modulation in Ge-rich SiGe waveguides in the mid-IR wavelength range up to 11 um

Waveguide integrated optical modulators in the mid-infrared (mid-IR) wavelength range are of significant interest for molecular spectroscopy in one hand, as on-chip synchronous detection can improve the performance of detection systems, and for free-space communications on the other hand, where optical modulators working in the atmospheric transparency windows are crucially missing. Here we report for the first time the demonstration of optical modulation in mid-IR photonic circuit reaching wavelengths larger than 8 um. Moreover, optical modulation in an unprecedented wavelength range, from 5.5 to 11 um wavelength is shown, relying on a broadband Ge-rich graded-SiGe platform. This first demonstration is used as a proof of concept, to experimentally confirm the free-carrier absorption effect modeling. These results pave the way towards efficient high-performance electrically-driven integrated optical modulators in the mid-IR wavelength range.

physics.optics↗

arXiv2019

Trimming and ultra-wide bandwidth expansion of silicon frequency comb spectra with self-adaptive boundary waveguides

Dispersion engineering is among the most important steps towards a promising optical frequency comb. We propose a new and general approach to trim frequency combs using a self-adaptive boundary of the optical mode at different wavelengths in a sub-wavelength structured waveguide. The feasibility of ultra-wide bandwidth dispersion engineering comes from the fact that light at different wavelengths automatically self-adapts to slightly different effective spatial spans determined by the effective indices of the mode. Using this self-adaptive variation on the confinement, we open up the window of low-anomalous dispersion in a large wavelength range, and theoretically demonstrate frequency combs with improved bandwidths with respect to the state-of-art in several different waveguide configurations considered, for a matter of illustration, in the silicon photonic platform. This strategy opens up a new design space for trimming the spectrum of frequency combs using high-index-contrast platforms and provides benefit to various versatile nonlinear applications in which the manipulation of energy spacing and phase matching are pivotal.

physics.optics↗

arXiv2019

Self-adaptive waveguide boundary for wideband multi-mode four-wave mixing

We propose a new approach to provide wideband multi-mode four-wave mixing, independent of the intrinsic waveguide dispersion. We adopt concepts from quantum mechanics and sub-wavelength engineering to design an effective photon well, with a graded potential along the waveguide cross section, that provides flexible control over the mode confinement. The self-adaptive nature of the waveguide boundary allows different spatial modes with equi-spaced frequencies and shared propagation wavevector, automatically fulfilling both, energy conservation and wavevector phase matching conditions. Capitalizing on this concept, we show phase-matching among modes separated by 400 nm (bridging from telecom wavelengths to almost 2μm), with less than 5% deviation in a remarkably large bandwidth exceeding 300 nm. Furthermore, we also show the flexibility of the proposed approach that can be seamlessly adapted to different technology platforms with the same or different waveguide thicknesses. This strategy opens a new design space for versatile nonlinear applications in which the manipulation of energy spacing and phase matching is pivotal, e.g. all-optical signal processing with four-wave mixing, mid-infrared light generation, Brillouin scattering with selectable phonon energy, etc.

physics.optics↗

arXiv2018

Generating Fano Resonances in a single-waveguide nanobeam cavity for efficient electro-optical modulation

We propose a method for generating Fano resonance in a standalone silicon nanobeam cavity which eliminates the inconvenience from the unexpected side-coupled bus waveguide and unlocks new opportunities to develop ultra-compact and ultra-fast electro-optical modulators.. Taking advantage from a spatial-division multiplexing principle of operation between transverse electric modes, a sharp resonant mode and an efficient flat background mode are simultaneously generated in the same silicon channel for the realization of efficient Fano resonances. Unambiguous asymmetric spectrum lineshapes are thoroughly investigated using numerical and analytical methods and experimentally demonstrated in the near infra-red around lambda=1.55μm, presenting an extinction ratio of about 17dB for a delta lambda =56 pm wavelength detuning for the 1st cavity mode (Q-factor Q=34000), and higher than 23 dB extinction ratio for a delta lambda=366 pm detuning for the 2nd cavity mode (Q=5600). These extinction ratios are 10~15 dB larger than their Lorentzian counterparts exhibiting similar Q factors. Silicon Fano modulation based on plasma dispersion effect is proposed, for which an energy consumption as low as few fJ/bit is estimated. Fano cavity scheme addressed in this paper presents a great potential for low power consumption silicon optical modulators and provides anew insight to the advantages of Fano resonances for optical modulation schemes.

physics.optics↗

arXiv2018

Polarization and wavelength agnostic nanophotonic beam splitter

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 the silicon-on-insulator platform, state of the art Si 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-wideband polarization-insensitive optical power splitters, with relaxed fabrication tolerances. The proposed splitter relies on a single-mode slot waveguide which is transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate -3$\pm$0.5 dB polarization-independent transmission in an unprecedented 390 nm bandwidth (1260 - 1650 nm), even in the presence of waveguide width deviations as large as $\pm$25 nm.

physics.app-ph↗

arXiv2017

Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures

The high index contrast of the silicon-on-insulator (SOI) platform allows the realization of ultra-compact photonic circuits. However, this high contrast hinders the implementation of narrow-band Bragg filters. These typically require corrugations widths of a few nanometers or double-etch geometries, hampering device fabrication. Here we report, for the first time, on the realization of SOI Bragg filters based on sub-wavelength index engineering in a differential corrugation width configuration. The proposed double periodicity structure allows narrow-band rejection with a single etch step and relaxed width constraints. Based on this concept, we experimentally demonstrate a single-etch, $\mathbf{220\,nm}$ thick, Si Bragg filter featuring a corrugation width of $\mathbf{150\,nm}$, a rejection bandwidth of $\mathbf{1.1\,nm}$ and an extinction ratio exceeding $\mathbf{40\,dB}$. This represents a ten-fold width increase compared to conventional single-periodicity, single-etch counterparts with similar bandwidths.

physics.optics↗

arXiv2017

High-quality photonic entanglement for wavelength-multiplexed quantum communication based on a silicon chip

We report an efficient energy-time entangled photon-pair source based on four-wave mixing in a CMOS-compatible silicon photonics ring resonator. Thanks to suitable optimization, the source shows a large spectral brightness of 400\,pairs of entangled photons /s/MHz for $\rm 500\,μW$ pump power. Additionally, the resonator has been engineered so as to generate a frequency comb structure compatible with standard telecom dense wavelength division multiplexers. We demonstrate high-purity energy-time entanglement, i.e., free of photonic noise, with near perfect raw visibilities ($>$~98\%) between various channel pairs in the telecom C-band. Such a compact source stands as a path towards more complex quantum photonic circuits dedicated to quantum communication systems.

quant-ph↗

arXiv2016

Long-period suspended silicon Bragg grating filter for hybrid near- and mid-infrared operation

The large transparency window of silicon, covering the 1.1 um 8 um wavelength range, makes it a promising platform for the implementation of photothermal-based absorption spectrometers. These devices indirectly sense absorption in the mid-infrared (MIR) by using near-infrared (NIR) wavelengths, thereby enabling the realization of MIR absorption spectrometers without the need for MIR photodetectors. Nevertheless, due to their comparatively large index contrast and cross-sections, MIR Si strip waveguides are multi-mode at NIR wavelengths, hindering device implementation. Here we present, for the first time, an integrated Bragg grating waveguide filter for hybrid near- and mid-infrared operation. Specifically, the filter is implemented in a single-etch suspended silicon corrugated waveguide with an effectively single-mode operation in NIR region for a waveguide cross-section as large as 0.5 um x 1.1 um. At the same time, the waveguide supports single-mode propagation in MIR region. We demonstrate a long-period waveguide Bragg grating yielding a sharp third-order Bragg resonance for the fundamental waveguide mode and radiating the higher order modes. We experimentally demonstrate a notch filter with a 4nm bandwidth and 40 dB extinction ratio with a temperature-dependent Bragg wavelength shift of 70pm/K.

physics.optics↗