Roberto Morandotti

Institut National de la Recherche Scientifique | INRS · Energy, Materials and Telecommunications Research Centre

Photonic RF transversal signal processors, which are equivalent to reconfigurable electrical digital signal processors but implemented with photonic technologies, are attractive for high-speed information processing. Optical microcombs are extremely powerful as sources for RF photonics since they can generate many wavelength channels from compact m...

We report the observation of Brillouin backscattering in a 50-cm long spiral high-index doped silica chip waveguide and measured a Brillouin frequency shift of 16 GHz which is in very good agreement with theoretical predictions and numerical simulations based on the elastodynamics equation.

Nonlinear materials are cornerstones in modern optics and electronics. Strong dependence on the intrinsic properties of particular materials, however, inhibits at-will extensions of demanding nonlinear effects, especially those second-order ones, to widely-adopted centrosymmetric materials (for example, silicon) and technologically-important burgeo...

Synthetic dimensions (SDs) opened the door for exploring previously inaccessible phenomena in high-dimensional synthetic space. However, construction of synthetic lattices with desired coupling properties is a challenging and unintuitive task, largely limiting the exploration and current application of SD dynamics. Here, we overcome this challenge...

A hallmark of symmetry-protected topological phases are topological boundary states, which are immune to perturbations that respect the protecting symmetry. It is commonly believed that any perturbation that destroys such a topological phase simultaneously destroys the boundary states. However, by introducing and exploring a weaker sub-symmetry req...

Photonic-based implementation of advanced computing tasks is a potential alternative to mitigate the bandwidth limitations of electronics. Despite the inherent advantage of a large bandwidth, photonic systems are generally bulky and power-hungry. In this respect, all-pass spectral phase filters enable simultaneous ultrahigh speed operation and mini...

Plasmonic polymeric nanoassemblies offer valuable opportunities in photoconversion applications. Localized surface plasmon mechanisms behind such nanoassemblies govern their functionalities under light illumination. However, an in-depth investigation at the single nanoparticle (NP) level is still challenging, especially when the buried interface is...

Multidimensional imaging of transient events has proven pivotal in unveiling many fundamental mechanisms in physics, chemistry, and biology. In particular, real-time imaging modalities with ultrahigh temporal resolutions are required for capturing ultrashort events on picosecond timescales. Despite recent approaches witnessing a dramatic boost in h...

The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals. Despite tremendous efforts in engineering synthetic cold-atom, as well as electronic and photonic lattices to explore orbital physic...

Optical microcombs represent a new paradigm for generating laser frequency combs based on compact chip-scale devices, which have underpinned many modern technological advances for both fundamental science and industrial applications. Along with the surge in activity related to optical micro-combs in the past decade, their applications have also exp...

The simultaneous advances in artificial neural networks and photonic integration technologies have spurred extensive research in optical computing and optical neural networks (ONNs). The potential to simultaneously exploit multiple physical dimensions of time, wavelength and space give ONNs the ability to achieve computing operations with high para...

Communication links operating at terahertz frequencies are envisioned to provide a revolutionary enhancement of data transmission. As fundamental building blocks, waveguides play an indispensable role in future terahertz networks, not only transporting data streams with unprecedented data rates, but also serving as a versatile platform for signal p...

Towards meeting the strict demands of practical quantum networks, we leverage coherent energy redistribution for noise-tolerant quantum signal processing. We demonstrate the enhancement of noisy biphoton coincidence-to-accidental ratios by up to 3.8 times.

Terahertz (THz) on-chip communication with compact topological devices and high-rate data transmission could enable future artificial-intelligence and cloud-based technologies. A key challenge in reaching such goals is controlled THz generation, confinement and detection, preferably in a compact integrated device. Recently, we have developed THz fr...

Optical microcombs represent a new paradigm for generating laser frequency combs based on compact chip-scale devices, which have underpinned many modern technological advances for both fundamental science and industrial applications. Along with the surge in activity related to optical microcombs in the past decade, their applications have also expe...

We report the coherent generation and detection of terahertz (THz) pulses featuring a spectral bandwidth in the range of 0.1-9 THz achieved via the use of a high repetition rate (250 kHz), low pulse energy (6.2 µJ) laser system. More specifically, we test and evaluate a solid-state biased coherent detection device in combination with a spintronic e...

Laser cavity-soliton microcombs are robust optical pulsed sources, usually implemented with a microresonator-filtered fibre laser. In such a configuration, a nonlinear microcavity converts the narrowband pulse resulting from bandwidth-limited amplification to a background-free broadband microcomb. Here, we theoretically and experimentally study the...

Since its first demonstration in 1995, terahertz time-domain imaging has attracted an increasingly growing interest for its ability to reveal spectral fingerprints of materials, probe changes in refractive index and absorption, as well as detect the inner structure of complex objects via time-of-flight measurements. Practically, however, its widesp...

The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals. Despite tremendous efforts in engineering synthetic cold-atom, as well as electronic and photonic lattices to explore orbital physic...

Optical neural networks (ONNs), or optical neuromorphic hardware accelerators, have the potential to dramatically enhance the computing power and energy efficiency of mainstream electronic processors, due to their ultralarge bandwidths of up to 10s of terahertz together with their analog architecture that avoids the need for reading and writing dat...

In this Chapter we will illustrate the state-of-art in the generation of dissipative solitons in Kerr microresonator-based systems. After a brief introduction on the origin of this field of research, we will discuss the modeling of these microcavities using the generalized Lugiato-Lefever equation. Further, we will discuss the different techniques...

In many disciplines, states that emerge in open systems far from equilibrium are determined by a few global parameters 1,2 . These states can often mimic thermodynamic equilibrium, a classic example being the oscillation threshold of a laser ³ that resembles a phase transition in condensed matter. However, many classes of states cannot form spontan...

The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals. Despite tremendous efforts in engineering synthetic cold-atom, electronic and photonic lattices to explore orbital physics, thus far...

A simple, practical method based on electro‐optic gating is experimentally shown to improve the temporal resolution of single‐photon detection by more than 16 times. Delay times between ultrafast single photons and a reference clock are stretched by a desired programmable sampling gate factor, allowing reconstruction of delay histograms with ≈0.001...

Digital signal processing has become central to many fields, from coherent optical telecommunications where it is used to compensate signal impairments, to video image processing. Image processing in particular is important for observational astronomy, medical diagnosis, autonomous driving, big data and particularly artificial intelligence. Digital...

Compact terahertz (THz) functional devices are greatly sought after for high-speed wireless communication, biochemical sensing, and non-destructive inspection. However, controlled THz generation, along with transport and detection, has remained a challenge especially for chip-scale devices due to low-coupling efficiency and unavoidable absorption l...

A hallmark of symmetry-protected topological phases (SPTs) are topologically protected boundary states, which are immune to perturbations that respect the protecting symmetry. It is commonly believed that any perturbation that destroys an SPT phase simultaneously destroys the boundary states. However, by introducing and exploring a weaker sub-symme...

The need to measure high repetition rate ultrafast processes cuts across multiple areas of science. The last decade has seen tremendous advances in the development and application of new techniques in this field, as well as many breakthrough achievements analyzing non-repetitive optical phenomena. Several approaches now provide convenient access to...

Waveguides play a pivotal role in the full deployment of terahertz communication systems. Besides signal transporting, innovative terahertz waveguides are required to provide versatile signal-processing functionalities. Despite fundamental components, such as Bragg gratings, have been recently realized, they typically rely on complex hybridization,...

Our ability to generate new distributions of light has been remarkably enhanced in recent years. At the most fundamental level, these light patterns are obtained by ingeniously combining different electromagnetic modes. Interestingly, the modal superposition occurs in the spatial, temporal as well as spatio-temporal domain. This generalized concept...

We discuss our recent demonstrations of nonlinear control of topological states in cw-laser-written photonic lattices of different symmetries, including manipulation of edge and corner states in higher-order topological insulators and dynamically emerging nonlinear topological phenomena.

We theoretically and experimentally demonstrate the concept of sub-symmetry in symmetry-protected topological systems, wherein the original symmetry is partially broken so bulk topological invariant no longer exists, but some edge states are still topologically protected.

We experimentally demonstrate photonic higher-order topological orbital corner states in laser-written breathing Kagome lattices, unveiling their charaterisitic dipole-like mode distribution and dynamical rotation in presence of optical nonlinearity.

We demonstrate a new waveguide geometry, namely a four-wire waveguide, which acts as a terahertz polarization-division multiplexer and a novel platform to realize versatile signal-processing functionalities into independent channels over a broadband terahertz frequency range.

We demonstrate corner states in trivial and nontrivial 2D SSH lattices diagonally stretched to exhibit both HOTI and higher-order semimetal-like features and examine the underlying topological mechanisms from the calculated spectral phase density.

We demonstrate a scalable, autonomous on-chip pulse shaping system based on temporal coherence synthesis. The inclusion of smart optimization algorithms enables robust, and reconfigurable pulse-shaping over a wide range of input and target durations.

We report higher-order orbital corner states in two-dimensional Su-Schrieffer-Heeger (SSH) photonic lattices, representing an orbital HOTI model. With appropriately shaped input beams, we explore orbital corner excitations in topologically nontrivial and trivial regimes.

We report two types of distinct corner states in breathing Kagome lattices with bearded edge truncation. One type exists only in the topologically nontrivial regime, while the other preserves in both trivial and nontrivial regimes.

We use a low-loss, user-friendly on-chip interferometer cascade to exploit the concept of temporal coherence synthesis for the shaping of optical pulses and, first-time, of the joint spectral intensity of broadband correlated photon pairs.

Starting from 175-fs-long pulses at 1035 nm, we directly generate 20 μJ, 4.6 fs visible pulses through the nonlinear mixing between the spatial modes of a 3-m-long Ar-filled hollow-core fiber, without any pulse post-compression.

We demonstrate nonlinear generation and topologically tuned confinement of THz waves in a wedge-shaped Su-Schrieffer-Heeger lattice laser-written in a lithium-niobate chip, examining THz defect modes from band structure and analyzing their robustness to chiral perturbation.

We demonstrate a universal optical vector convolutional accelerator operating at 11 Tera-OPS, generating convolutions of images of 250,000 pixels with 8-bit resolution for 10 kernels simultaneously. We use the same hardware to form a deep optical CNN with ten output neurons, achieving successful recognition of full 10 digits with 88% accuracy. Our...

Optical neural networks (ONNs), or optical neuromorphic hardware accelerators, have the potential to dramatically enhance the computing power and energy efficiency of mainstream electronic processors, due to their ultra-large bandwidths of up to 10's of terahertz together with their analog architecture that avoids the need for reading and writing d...

Slow nonlinearities are critical in microresonator-based frequency combs, regulating essential phenomena, from stability to soliton starting and formation. We discuss their effect in a microresonator-filtered fiber laser.

We demonstrate Yb laser (170fs) propagation in large a core hollow-core fiber (HCF) with 97.4% transmission. It serves as a pre-compression stage to achieve 1.3 cycle pulses in a second step with 70% overall efficiency

we directly generate 20 µJ, 4.6 fs visible pulses (~2 cycles) without any post-compression by coupling 175-fs-long infrared pulses into a 3-m-long Ar-filled hollow-core fiber and exploiting the nonlinear mixing between its spatial modes.

We demonstrate orbital corner states in photonic higher-order topological insulators (HOTIs), comparing the p -band characteristics between two-dimensional Su-Schrieffer-Heeger (SSH) and breathing Kagome lattices. The orbital corner excitations are explored in topological nontrivial and trivial regimes.

We show the free-running frequency stability and the frequency control of a micro-comb system comprising a micro-ring nested into an amplifying fibre cavity.

We exploit standard silicon-based chips and fiber telecommunications components to generate and process complex entangled photon states in the discrete time and frequency domains (two-level time-entangled photons, d-level frequency-entangled photon pairs, and three-level cluster states).

We demonstrate an electro-optic sampling technique for high-resolution acquisition of few-photon signals. The temporal features of a biphoton distribution are observed with 98 ps resolution using slow detectors with a response extending >1 ns.

We demonstrate an RF photonic fractional Hilbert transformer based on an integrated Kerr micro-comb source featuring a record low free spectral range of 48.9 GHz, yielding 75 microcomb lines across the C-band. By programming and shaping the comb lines according to calculated tap weights, we demonstrate that the Hilbert transformer can achieve tunab...

Extremely short, high-energy pulses are essential in modern ultrafast science. In a seminal paper in 1996¹, Nisoli and co-workers demonstrated the first intense pulse compression employing a gas-filled hollow-core fibre. Despite the huge body of scientific work on this technology stemming from ultrafast and attosecond research, here we identify an...

Compact terahertz (THz) functional devices are greatly sought after for high-speed wireless communication, biochemical sensing, and non-destructive inspection. However, conventional devices to generate and guide THz waves are afflicted with diffraction loss and disorder due to inevitable fabrication defects. Here, based on the topological protectio...

Multi-level (qudit) entangled photon states are a key resource for both fundamental physics and advanced applied science, as they can significantly boost the capabilities of novel technologies such as quantum communications, cryptography, sensing, metrology, and computing. The benefits of using photons for advanced applications draw on their unique...

We demonstrate dynamical topological phase transitions in evolving Su-Schrieffer-Heeger lattices made of interacting soliton arrays, which are entirely driven by nonlinearity and thereby exemplify an emergent nonlinear topological phenomenon. The phase transitions occur from the topologically trivial-to-nontrivial phase in periodic succession with...

Soliton crystal micro-combs are powerful tools as sources of multiple wavelength channels for radio frequency (RF) signal processing. They offer a compact device footprint, a large number of wavelengths, very high versatility, and wide Nyquist bandwidths. Here, we demonstrate integral order RF signal processing functions based on a soliton crystal...

Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical nois...

High‐bandwidth metallic coaxial nanolasers are of high interest to investigate laser physics such as thresholdless coherence transitions, and have a large variety of promising applications enabled by their ultrasmall size and large spectral bandwidth. Optical coherence properties are commonly characterized in Hanbury‐Brown and Twiss experiments. Ho...

Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical nois...

The generation of user-defined optical temporal waveforms with picosecond resolution is an essential task for many applications, ranging from telecommunications to laser engineering. Realizing this functionality in an on-chip reconfigurable platform remains a significant challenge. Towards this goal, autonomous optimization methods are fundamental...