arXiv subjects

Pascal Szriftgiser

Publications and source records attributed to Pascal Szriftgiser.

At least 19 recordsLinked to original sources

arXiv2026

Dispersion-Engineered Terahertz Silicon Interconnects Enabling Terabit-Scale Data Links

The rapid growth of artificial intelligence (AI) and data-centric computing is driving exabyte-scale data transfer, pushing conventional interconnect technologies toward fundamental bandwidth and energy limits. Although optical interconnects provide high-capacity and long-reach communication, their complexity and energy overhead limit scalability in short-reach chiplet-based and on-chip systems. Terahertz (THz) silicon interconnects offer a promising alternative by bridging electronics and photonics in compact, complementary metal-oxide-semiconductor (CMOS)-compatible platforms capable of high bandwidth and low latency. However, practical THz interconnects require simultaneous multi-band operation, dual-polarization support, low propagation loss, low group-velocity dispersion (GVD), and terabit-per-second throughput, while avoiding Bragg-induced stopbands and dispersion penalties at high frequencies. Here, we demonstrate a CMOS-compatible, centimetre-scale, multi-band on-chip THz data link achieving an aggregate throughput of 1.004 Tbps. The performance is enabled by suppressing Bragg-induced stopbands using dispersion-engineered, effective-medium-supported unclad silicon waveguides, resulting in flat transmission and low-ripple group delay across multiple THz bands. The waveguide platform operates from 220 to 500 GHz and supports both transverse-electric (TE) and transverse-magnetic (TM) polarizations with low path loss, low bending loss, and low GVD. Fourteen channels in a straight waveguide and twelve channels in a 90$^\circ$ bend achieve aggregate data rates of 1.004 Tbps and 0.895 Tbps, respectively, with GVD as low as 0.15 ps$^2$/mm over the full operating band. These results establish a scalable and energy-efficient THz interconnect platform for high-density on-chip and chip-to-chip communication fabrics targeting next-generation AI systems and emerging 6G technologies.

physics.optics↗

arXiv2026

Terahertz Communications Using Effective-Medium-Slot Waveguides

All-dielectric effective-medium-clad waveguides have been widely exploited in terahertz communications owing to their extremely low loss, low dispersion, and broad bandwidth. In this work, we propose a substrateless effective-medium-slot waveguide. Additionally, we introduce a taper-free interface that allows terahertz waves to directly couple from a metallic hollow waveguide without requiring dielectric insertion. By engineering slot couplers with an effectivemedium channel for impedance and modal matching, the waveguide achieves a fractional 3-dB bandwidth of 40% with a maximum coupling efficiency of 90% in the WR-2.2 band (330-500 GHz). By employing a broadband uni-traveling-carrier photodiode transmitter and sub-harmonic mixer receivers, we achieve an aggregated data rate of 0.8 Tbit/s with quadrature amplitude modulation schemes across 14 channels from 330-600 GHz. The effective-medium-slot waveguide platform yields robust broadband coupling with enhanced mechanical protection, offering reliable interconnects for ultra-high-speed terahertz integrated systems.

physics.optics↗

arXiv2024

Relation between interface symmetry and propagation robustness along domain walls based on valley topological photonic crystals

Valley photonic crystals provide efficient designs for the routing of light through channels in extremely compact geometries. The topological origin of the robust transport and the specific geometries under which it can take place have been questioned in recent works. In this article, we introduce a design for valley photonic crystals with richer arrangement possibilities than the standard valley photonic crystals based on two holes of different sizes in the unit cell. Our approach is based on the permutation of three sets of rhombi in an hexagonal lattice to investigate the interplay between Berry curvature, valley Chern number and chirality of interfaces to achieve robust edge-modes propagation along domain walls. We study three types of interfaces with different symmetries: the non-chiral interface with glide-mirror symmetry commonly used in honeycomb-type valley crystals, and two chiral interfaces with or without inversion symmetry of the adjacent bulk lattices. In the latter case, no valley topology is expected. We show that for the three families, edges preserving the shape of the interface through 120{\deg} sharp corners can sustain edge-modes with comparable robustness. Moreover, interfaces with glide-mirror symmetry offer promising performances in circuits with more exotic configurations, like 60{\deg} and 90{\deg} corners or arbitrary curves in which valley preservation is not guaranteed. Our work raises questions about the topological origin of the robustness of transport in valley photonic crystals, discusses the role of the chirality of the interfaces in the propagation around sharp corners, and provides a lattice scheme with broad design possibilities.

physics.optics↗

arXiv2024

Gain-controlled taming of recurrent modulation instability

We show how the recurrence phenomenon characteristic of the nonlinear stage of induced modulational instability in a passive fiber is affected by forcing. An additional linear amplification, even if extremely weak, induces separatrix crossing in correspondence of critical values of the gain around which the recurrence process considerably slows down, switching between dynamical orbits of different kind. We present evidence for such phenomenon in a fiber optics experiment where the gain is finely tuned by means of Raman amplification. A theoretical explanation is also provided that matches almost perfectly with our experimental results.

physics.optics↗

arXiv2024

Exploring quantum criticality in a 4D quantum disordered system

Phase transitions are prevalent throughout physics, spanning thermal phenomena like water boiling to magnetic transitions in solids. They encompass cosmological phase transitions in the early universe and the transition into a quark-gluon plasma in high-energy collisions. Quantum phase transitions, particularly intriguing, occur at temperatures near absolute zero and are driven by quantum fluctuations rather than thermal ones. The strength of the fluctuations is very sensitive to the dimensionality of the physical systems, which determines the existence and nature of phase transitions. Low-dimensional systems often exhibit suppression of phase transitions, while high-dimensional systems tend to exhibit mean-field-like behavior. The localization-delocalization Anderson transition stands out among quantum phase transitions, as it is thought to retain its non-mean-field character across all dimensions. This work marks the first observation and characterization of the Anderson transition in four dimensions using ultracold atoms as a quantum simulator with synthetic dimensions. We characterize the universal dynamics in the vicinity of the phase transition. We measure the critical exponents describing the scale-invariant properties of the critical dynamics, which are shown to obey Wegner's scaling law. Our work is the first experimental demonstration that the Anderson transition is not mean-field in dimension four.

cond-mat.dis-nn↗

arXiv2023

On-chip Amorphous THz Topological Photonic Interconnects

Valley Hall photonic crystals (VPCs) offer the potential to create topological waveguides capable of guiding light through sharp bends on a chip. They can seamlessly integrate with functional components while occupying minimal space, making them a promising technology for terahertz (THz) topological photonic integrated circuits. However, a significant limitation for THz-scale integrated VPC-based devices has been the absence of arbitrary bend interconnects. Due to the crystalline symmetry, the traditional VPC designs restrict waveguides to the principal lattice axes (i.e., only 0-, 60- or 120- degree orientations). Here, we present an on-chip, all silicon implementation of deformed VPCs enabling topological waveguides with a variety of shapes and bends. Although the lattice is amorphous and lacks long-range periodicity, the topological protection of the waveguides is sustained by short-range order. We experimentally demonstrate the robust on-chip transmission of THz waves through waveguides of complicated shapes and arbitrary bends. We implement an amorphous lattice that serves as a frequency-dependent router capable of splitting the input signal into two perpendicular output ports, which cannot be achieved with an undeformed VPC. In addition, we showcase on-chip THz communication through 90 degree and P-shaped VPC waveguides, achieving data rates of 72 Gbit/s and 32 Gbit/s, respectively. Our findings demonstrate that the amorphous topological photonic crystals significantly enhance the adaptability of on-chip interconnections while preserving the performance of the topological waveguides.

physics.optics↗

arXiv2023

Scattering-matrix approach for a quantitative evaluation of the topological protection in valley photonic crystals

In this work, we use valley-topological triangular resonators coupled to an input waveguide to evaluate the quality of the topological protection. To that purpose, we first analyze via numerical simulations the existence of backward scattering at cavity corners or transmission with pseudo-spin conversion at the splitter between the input waveguide and the cavity. We evidence that a breakdown of topological protection takes place, in particular at sharp corners, which results in transmission minima and split-resonances, otherwise non-existent. In order to evaluate the small coupling coefficients associated to this breakdown, a phenomenological model based on an exact parameterization of scattering matrices at splitters and corners of the resonators is then introduced. By comparison with the numerical simulations, we are able to quantify the loss of topological protection at sharp bends and splitters. Finally, we use the obtained set of phenomenological parameters to compare the predictions of the phenomenological model with full numerical simulations for fractal-inspired cavities based on the Sierpi\'nski triangle construction. We show that the agreement is overall good, but shows more differences for the cavity composed of the smallest triangles. Our results suggest that even in a system exempt of geometrical and structural defects, topological protection is not complete at corners, sharp bends and splitters. However, simpler but predictive calculations can be realized with a phenomenological approach, allowing simulations of very large devices beyond the reach of standard simulation methods, which is crucial to design photonic devices which gather compactness and low losses through topological conduction of electromagnetic waves.

physics.optics↗

arXiv2022

Multiple symmetry breaking induced by weak damping in the Fermi-Pasta-Ulam-Tsingou recurrence process

We show that even small dissipation can strongly affect the Fermi-Pasta-Ulam-Tsingou recurrence phenomenon. Taking the fully nonlinear stage of modulational instability as an experimentally accessible example, we show that the linear attenuation induces the symmetry of the recurrence to be broken through separatrix crossing occurring at multiple critical values of the attenuation. We provide experimental evidence for this phenomenon in a fiber optics experiment designed in such a way that the effective losses can be carefully tailored by techniques based on Raman amplification.

nlin.PS↗

arXiv2022

Observation of the noise-driven thermalization of the Fermi-Pasta-Ulam-Tsingou recurrence in optical fibers

We report the observation of the thermalization of the Fermi-Pasta-Ulam-Tsingou recurrence process in optical fibers. We show the transition from a reversible regime to an irreversible one, revealing a spectrally thermalized state. To do so, we actively compensate the fiber loss to make the observation of several recurrences possible. We inject into the fiber a combination of three coherent continuous waves, which we call Fourier modes, and a random noise. We enhance the noise-driven modulation instability process against the coherent one by boosting the input noise power level to speed up the evolution to the thermalization. The distributions of the Fourier modes power along the fiber length are recorded thanks to a multi-heterodyne time-domain reflectometer. At low input noise levels, we observe up to four recurrences. Whereas, at higher noise levels, the Fourier modes fade into the noise-driven modulation instability spectrum revealing that the process reached an irreversible thermalized state.

nlin.PS↗

arXiv2022

Localization properties of the asymptotic density distribution of a one-dimensional disordered system

Anderson localization is the ubiquitous phenomenon of inhibition of transport of classical and quantum waves in a disordered medium. In dimension one, it is well known that all states are localized, implying that the distribution of an initially narrow wave-packet released in a disordered potential will, at long time, decay exponentially on the scale of the localization length. However, the exact shape of the stationary localized distribution differs from a purely exponential profile and has been computed almost fifty years ago by Gogolin. Using the atomic quantum kicked rotor, a paradigmatic quantum simulator of Anderson localization physics, we study this asymptotic distribution by two complementary approaches. First, we discuss the connection of the statistical properties of the system's localized eigenfunctions and their exponential decay with the localization length of the Gogolin distribution. Next, we make use of our experimental platform, realizing an ideal Floquet disordered system, to measure the long-time probability distribution and highlight the very good agreement with the analytical prediction compared to the purely exponential one over 3 orders of magnitude.

cond-mat.dis-nn↗

arXiv2021

Multi-frequency telecom fibered laser system for potassium laser cooling

We describe a compact and versatile multi-frequency laser system for laser-cooling potassium atoms, by frequency doubling a fiber-optic telecom beam ($\simeq 1534$ or $1540$~nm). Low-power fiber-based telecom lasers and components generate a single beam containing the cooling and repumper half frequencies, subsequently amplified by high-power amplifier. A final free-space SHG stage generates a single beam with typically 2.5 W at quasi-resonant frequencies ($\simeq 767$ or $770$~nm) with high-quality mode and ready for laser cooling. This allowed to trap up to $4\times10^9$ $^{41}$K atoms with fast loading times (2.5 s) at sub-Doppler temperatures of 16~$μ$K. This opens promising perspectives towards versatile and transportable ultracold atom setups.

physics.atom-ph↗

arXiv2021

Computer Algebra in Physics: The hidden SO(4) symmetry of the hydrogen atom

Pauli first noticed the hidden SO(4) symmetry for the Hydrogen atom in the early stages of quantum mechanics [1]. Departing from that symmetry, one can recover the spectrum of a spinless hydrogen atom and the degeneracy of its states without explicitly solving Schrödinger's equation [2]. In this paper, we derive that SO(4) symmetry and spectrum using a computer algebra system (CAS). While this problem is well known [3, 4], its solution involves several steps of manipulating expressions with tensorial quantum operators, simplifying them by taking into account a combination of commutator rules and Einstein's sum rule for repeated indices. Therefore, it is an excellent model to test the current status of CAS concerning this kind of quantum-and-tensor-algebra computations. Generally speaking, when capable, CAS can significantly help with manipulations that, like non-commutative tensor calculus subject to algebra rules, are tedious, time-consuming and error-prone. The presentation also shows a pattern of computer algebra operations that can be useful for systematically tackling more complicated symbolic problems of this kind.

cs.SC↗

arXiv2020

"Extraordinary" modulation instability in optics and hydrodynamics

The classical theory of modulation instability (MI) attributed to Bespalov-Talanov in optics and Benjamin-Feir for water waves is just a linear approximation of nonlinear effects and has limitations that have been corrected using the exact weakly nonlinear theory of wave propagation. We report results of experiments in both, optics and hydrodynamics, which are in excellent agreement with nonlinear theory. These observations clearly demonstrate that MI has wider band of unstable frequencies than predicted by the linear stability analysis. The range of areas where the nonlinear theory of MI can be applied is actually much larger than considered here.

nlin.PS↗

arXiv2019

Acetylene-based frequency stabilization of a laser system for potassium laser cooling

We demonstrate a laser frequency stabilization technique for laser cooling of Potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrationel transitions of the acetylene molecule ($12$C$_2$H$_2$). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the $^{41}$K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.

physics.atom-ph↗

arXiv2018

Experimental realization of an ideal Floquet disordered system

The atomic Quantum Kicked Rotor is an outstanding "quantum simulator" for the exploration of transport in disordered quantum systems. Here we study experimentally the phase-shifted quantum kicked rotor, which we show to display properties close to an ideal disordered quantum system, opening new windows into the study of Anderson physics.

cond-mat.quant-gas↗

arXiv2018

Optoelectronic nibbling of laser linewidth using a Brillouin-assisted optical phase-locked loop

We demonstrate that the implementation of phase-locked loop forbidding multimode operation of a long Brillouin resonator also leads to a dramatic reduction of the optical phase noise of the pump itself. In the case of a continuous Er,Yb:glass laser, a reduction by more than 90 dB at 100 Hz of the carrier is observed. This yields an optical linewidth estimated narrower than 2 Hz for the pump laser. The method being independent of the laser wavelength, it can be applied to almost any laser.

physics.optics↗

arXiv2018

Ratchet Effect in the Quantum Kicked Rotor and its Destruction by Dynamical Localization

We study experimentally a quantum kicked rotor with broken parity symmetry, supporting a ratchet effect due to the presence of a classical accelerator mode. We show that the short-time dynamics is very well described by the classical dynamics, characterized by a strongly asymmetric momentum distribution with directed motion on one side, and an anomalous diffusion on the other. At longer times, quantum effects lead to dynamical localization, causing an asymptotic resymmetrization of the wave function.

quant-ph↗

arXiv2018

Experimental observation of time singularity in classical-to-quantum chaos transition

The emergence of chaotic phenomena in a quantum system has long been an elusive subject. Experimental progresses in this subject have become urgently needed in recent years, when considerable theoretical studies have unveiled the vital roles of chaos in a broad range of topics in quantum physics. Here, we report the first experimental observation of time singularity, that signals a classical-to-quantum chaos transition and finds its origin in the {\it sudden change} in system's memory behaviors. The time singularity observed is an analog of the "dynamical quantum phase transition" (DQPT) -- proposed very recently for regular systems -- in chaotic systems, but with totally different physical origin.

cond-mat.dis-nn↗