arXiv subjects

Marco Liscidini

Publications and source records attributed to Marco Liscidini.

At least 55 records · Page 3Linked to original sources

arXiv2022

Super spontaneous four-wave mixing in an array of silicon microresonators

Composite optical systems can show compelling collective dynamics. For instance, the cooperative decay of quantum emitters into a common radiation mode can lead to superradiance, where the emission rate of the ensemble is larger than the sum of the rates of the individual emitters. Here, we report experimental evidence of super spontaneous four-wave mixing (super SFWM), an analogous effect for the generation of photon pairs in a parametric nonlinear process on an integrated photonic device. We study this phenomenon in an array of microring resonators on a silicon photonic chip coupled to bus waveguides. We measured a cooperative pair generation rate that always exceeds the incoherent sum of the rates of the individual resonators. We investigate the physical mechanisms underlying this collective behaviour, clarify the impact of loss, and address the aspects of fundamental and technological relevance of our results.

quant-ph↗

arXiv2022

Single-photon nonlinearities and blockade from a strongly driven photonic molecule

Achieving the regime of single-photon nonlinearities in photonic devices just exploiting the intrinsic high-order susceptibilities of conventional materials would open the door to practical semiconductor-based quantum photonic technologies. Here we show that this regime can be achieved in a triply resonant integrated photonic device made of two coupled ring resonators, without necessarily requiring low volume confinement, in a material platform displaying an intrinsic third-order nonlinearity. By strongly driving one of the three resonances of the system, a weak coherent probe at one of the others results in a strongly suppressed two-photon probability at the output, evidenced by antibunched second-order correlation function at zero-time delay under continuous wave driving.

quant-ph↗

arXiv2022

Resonant and non-resonant integrated third order parametric down-conversion

Third order parametric down-conversion describes a class of nonlinear processes in which a pump photon can be down-converted into triplets of photons. It has been identified as a source of non-classical light, with capabilities beyond those offered by better-established processes such as spontaneous four-wave mixing. Here we discuss the implementation of TOPDC in integrated photonic systems. We derive equations for the rates of TOPDC in a non-resonant (waveguide) and resonant (microring) platform, such that the scaling with experimental parameters can be plainly seen. We find that generally non-resonant platforms should be pursued for spontaneous TOPDC (SpTOPDC), whereas resonant platforms are more suitable for stimulated TOPDC (StTOPDC). We present a sample calculation for TOPDC rates in sample systems with conservative and accessible parameters. We find that StTOPDC should be observable with the current fabrication technology, and that with some progress in the design of TOPDC platforms, integrated SpTOPDC too could be demonstrated in the near term.

quant-ph↗

arXiv2022

Generation of Photon Pairs by Stimulated Emission in Ring Resonators

Third-order parametric down-conversion (TOPDC) describes a class of nonlinear interactions in which a pump photon is converted into a photon triplet. This process can occur spontaneously, or it can be stimulated by seeding fields. In the former case, one typically has the generation of non-Gaussian states of light. In the latter, the situation is more variegated, for stimulated TOPDC (StTOPDC) can be implemented in many ways, depending on the number and properties of the seeding fields. Here we show that StTOPDC can be exploited for the generation of quantum correlated photon pairs. We examine the peculiar features of this approach when compared with second-order spontaneous parametric down-conversion and spontaneous four-wave mixing. We model StTOPDC in a microring resonator, predicting observable generation rates in a microring engineered for third-harmonic generation. We conclude that if the experimental difficulties associated with implementing StTOPDC can be overcome, it may soon be possible to demonstrate this process in resonant integrated devices.

quant-ph↗

arXiv2020

Characterization of photon pairs generated by a silicon ring resonator under electrical self-pumping

We report on the generation of nonclassical states of light in a silicon ring resonator in a selfpumping scheme. The ring is inserted in a lasing cavity, for which it acts as a filter, so that the lasing always occurs within a selected ring resonance, without active stabilization of the resonance frequency. We show the emission of coincident photon pairs and study their correlation properties through the reconstruction of the measurements via stimulated emission.

quant-ph↗

arXiv2020

Long-range Bloch Surface Waves in Photonic Crystal Ridges

We theoretically study light propagation in guided Bloch surface waves (BSWs) supported by photonic crystal ridges. We demonstrate that low propagation losses can be achieved just by a proper design of the multilayer to obtain photonic band gaps for both light polarizations. We present a design strategy based on a Fourier analysis that allows one to obtain intrinsic losses as low as 5 dB/km for a structure operating in the visible spectral range. These results clarify the limiting factors to light propagation in guided BSWs and represent a fundamental step towards the development of BSW-based integrated optical platforms.

physics.optics↗

arXiv2018

Strong Nonlinear Coupling due to Induced Photon Interaction on a Si$_{3}$N$_{4}$ Chip

Second-order optical processes lead to a host of applications in classical and quantum optics. With the enhancement of parametric interactions that arise due to light confinement, on-chip implementations promise very-large-scale photonic integration. But as yet there is no route to a device that acts at the single photon level. Here we exploit the $χ^{(3)}$ nonlinear response of a Si$_{3}$N$_{4}$ microring resonator to induce a large effective $χ^{(2)}$. Effective second-order upconversion (ESUP) of a seed to an idler can be achieved with 74,000 %/W efficiency, indicating that single photon nonlinearity is within reach of current technology. Moreover, we show a nonlinear coupling rate of seed and idler larger than the energy dissipation rate in the resonator, indicating a strong coupling regime. Consequently we observe a Rabi-like splitting, for which we provide a detailed theoretical description. This yields new insight into the dynamics of ultrastrong effective nonlinear interactions in microresonators, and access to novel phenomena and applications in classical and quantum nonlinear optics.

physics.optics↗

arXiv2018

Nonlinear characterisation of a silicon integrated Bragg waveguide filter

Bragg waveguides are promising optical filters for pump suppression in spontaneous Four-Wave Mixing (FWM) photon sources. In this work, we investigate the generation of unwanted photon pairs in the filter itself. We do this by taking advantage of the relation between spontaneous and classical FWM, which allows for the precise characterisation of the nonlinear response of the device. The pair generation rate estimated from the classical measurement is compared with the theoretical value calculated by means of a full quantum model of the filter, which also allows to investigate the spectral properties of the generated pairs. We find a good agreement between theory and experiment, confirming that stimulated FWM is a valuable approach to characterise the nonlinear response of an integrated filter, and that the pairs generated in a Bragg waveguide are not a serious issue for the operation of a fully integrated nonclassical source.

quant-ph↗

arXiv2017

A Green function method to study thin diffraction gratings

The anomalous features in diffraction patterns first observed by Wood over a century ago have been the subject of many investigations, both experimental and theoretical. The sharp, narrow structures - and the large resonances with which they are sometimes associated - arise in numerous studies in optics and photonics. In this paper we present an analytical method to study diffracted fields of optically thin gratings that highlights the nonanalyticities associated with the anomalies. Using this approach we can immediately derive diffracted fields for any polarization in a compact notation. While our equations are approximate, they fully respect energy conservation in the electromagnetic field, and describe the large exchanges of energy between incident and diffracted fields that can arise even for thin gratings.

physics.optics↗

arXiv2017

Electromagnetic Field Enhancement in Bloch Surface Waves

We present a systematic comparison between guided modes supported by slab waveguides and Bloch Surface Waves (BSWs) propagating at the surface of truncated periodic multilayers. We show that, contrary to common belief, the best surface field enhancement achievable for guided modes in a slab waveguide is comparable to that observed for BSWs. At the same time, we demonstrate that, if one is interested in maximizing the electromagnetic energy density at a generic point of a dielectric planar structure, BSWs are often preferable to modes in which light is confined uniquely by total internal reflection. Since these results are wavelength independent and have been obtained by considering a very wide range of refractive indices of the structure constituent materials, we believe they can prove helpful in the design of future structures for the control and the enhancement of the light-matter interaction.

physics.optics↗

arXiv2017

Chip-based photon quantum state sources using nonlinear optics

The ability to generate complex optical photon states involving entanglement between multiple optical modes is not only critical to advancing our understanding of quantum mechanics but will play a key role in generating many applications in quantum technologies. These include quantum communications, computation, imaging, microscopy and many other novel technologies that are constantly being proposed. However, approaches to generating parallel multiple, customisable bi- and multi-entangled quantum bits (qubits) on a chip are still in the early stages of development. Here, we review recent developments in the realisation of integrated sources of photonic quantum states, focusing on approaches based on nonlinear optics that are compatible with contemporary optical fibre telecommunications and quantum memory infrastructures as well as with chip-scale semiconductor technology. These new and exciting platforms hold the promise of compact, low-cost, scalable and practical implementations of sources for the generation and manipulation of complex quantum optical states on a chip, which will play a major role in bringing quantum technologies out of the laboratory and into the real world.

physics.optics↗

arXiv2017

Parasitic Photon-Pair Suppression via Photonic Stop-Band Engineering

We calculate that an appropriate modification of the field associated with only one of the photons of a photon pair can suppress generation of the pair entirely. From this general result, we develop a method for suppressing the generation of undesired photon pairs utilizing photonic stop bands. For a third-order nonlinear optical source of frequency-degenerate photons we calculate the modified frequency spectrum (joint spectral intensity) and show a significant increase in a standard metric, the coincidence to accidental ratio. These results open a new avenue for photon-pair frequency correlation engineering.

quant-ph↗

arXiv2016

Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.

quant-ph↗

arXiv2015

Coherence in parametric fluorescence

We investigate spontaneous four wave mixing (SFWM) in a single-channel side-coupled integrated spaced sequence of resonators (SCISSOR). Analytic expressions for the number of photon pairs generated, as well as the biphoton wave function (joint spectral amplitude) describing the pairs, are derived and numerically computed for different pump pulse durations and numbers of ring resonators. In the limit of a long input pump pulse, we show a strong analogy between super-linear scaling of generation efficiency with respect to the number of rings in the structure and Dicke superradiance. More generally, we discuss in detail the factors that influence the shape of the biphoton wave function, as well as the conditions for observing super-SFWM.

quant-ph↗

arXiv2015

Optical resonators based on Bloch surface waves

A few recent works suggest the possibility of controlling light propagation at the interface of periodic multilayers supporting Bloch surface waves (BSWs), but optical resonators based on BSWs are yet to demonstrate. Here we discuss the feasibility of exploiting guided BSWs in a ring resonator configuration. In particular, we investigate the main issues related to the design of these structures, and we discuss about their limitations in terms of quality factors and dimensions. We believe these results might be useful for the development of a complete BSW-based platform for application ranging from optical sensing to the study of the light-matter interaction in micro and nano structures.

physics.optics↗

arXiv2014

Characterizing an Entangled-Photon Source with Classical Detectors and Measurements

Quantum state tomography (QST) is a universal tool for the design and optimization of entangled-photon sources. It typically requires single-photon detectors and coincidence measurements. Recently, it was suggested that the information provided by the QST of photon pairs generated by spontaneous parametric down-conversion could be obtained by exploiting the stimulated version of this process, namely difference frequency generation. In this protocol, so-called "stimulated-emission tomography" (SET), a seed field is injected along with the pump pulse, and the resulting stimulated emission is measured. Since the intensity of the stimulated field can be several orders of magnitude larger than the intensity of the corresponding spontaneous emission, measurements can be made with simple classical detectors. Here, we experimentally demonstrate SET and compare it with QST. We show that one can accurately reconstruct the polarization density matrix, and predict the purity and concurrence of the polarization state of photon pairs without performing any single-photon measurements.

quant-ph↗

arXiv2014

Bi-photon spectral correlation measurements from a silicon nanowire in the quantum and classical regimes

The growing requirement for photon pairs with specific spectral correlations in quantum optics experiments has created a demand for fast, high resolution and accurate source characterization. A promising tool for such characterization uses the classical stimulated process, in which an additional seed laser stimulates photon generation yielding much higher count rates, as recently demonstrated for a $χ^{(2)}$ integrated source in A.~Eckstein \emph{et al.}, Laser Photon. Rev. \textbf{8}, L76 (2014). In this work we extend these results to $χ^{(3)}$ sources, demonstrating spectral correlation measurements via stimulated four-wave mixing for the first time in a integrated optical waveguide, namely a silicon nanowire. We directly confirm the speed-up due to higher count rates and demonstrate that additional resolution can be gained when compared to traditional coincidence measurements. As pump pulse duration can influence the degree of spectral entanglement, all of our measurements are taken for two different pump pulse widths. This allows us to confirm that the classical stimulated process correctly captures the degree of spectral entanglement regardless of pump pulse duration, and cements its place as an essential characterization method for the development of future quantum integrated devices.

physics.optics↗

arXiv2014

A micrometer-scale integrated silicon source of time-energy entangled photons

Entanglement is a fundamental resource in quantum information processing. Several studies have explored the integration of sources of entangled states on a silicon chip but the sources demonstrated so far require millimeter lengths and pump powers of the order of hundreds of mWs to produce an appreciable photon flux, hindering their scalability and dense integration. Microring resonators have been shown to be efficient sources of photon pairs, but entangled state emission has never been demonstrated. Here we report the first demonstration of a microring resonator capable of emitting time-energy entangled photons. We use a Franson experiment to show a violation of Bell's inequality by as much as 11 standard deviations. The source is integrated on a silicon chip, operates at sub-mW pump power, emits in the telecom band with a pair generation rate exceeding 10$^7$ Hz per $nm$, and outputs into a photonic waveguide. These are all essential features of an entangled states emitter for a quantum photonic networks.

quant-ph↗