arXiv subjects

Amr S. Helmy

Publications and source records attributed to Amr S. Helmy.

At least 19 recordsLinked to original sources

arXiv2025

Towards Arbitrary Time-frequency Mode Squeezing with Self-conjugated Mode Squeezing in Fiber

Optical parametric amplification generates squeezed light in device-specific sets of time-frequency eigenmodes, and it has been widely accepted that detection and utilization of squeezing must comply with this modal constraint. We show that this constraint can be considerably relaxed under the continuous-wave pump and broadband phase-matching approximation, where the modal decomposition is non-unique. Specifically, any time-frequency mode with "self-conjugated" spectral symmetry can approximate a squeezing eigenmode, and partial homodyne detection can herald squeezing in arbitrary time-frequency modes. We demonstrate this using a high-efficiency, low-loss all-fiber source, measuring 4.38 +- 0.11dB and 0.88 +- 0.09 dB squeezing on partially coherent and chaotic self-conjugated modes. Using a bichromatic self-conjugated mode with reduced local-oscillator noise, we achieve 7.50 +- 0.12dB squeezing, which represents the highest level reported for fully guided-wave squeezing sources based on chi(2) and chi(3) nonlinearities.

quant-ph↗

arXiv2025

Silicon-Integrated Next-Generation Plasmonic Devices for Energy-Efficient Semiconductor Applications

Silicon-based integrated photonics has demonstrated significant advances in miniaturization and performance, yet critical challenges remain in achieving efficient on-chip communication at high bandwidths. Plasmonic devices on silicon and silicon-on-insulator substrates offer a promising solution, enabling subwavelength light confinement and enhanced light-matter interactions through hybrid modes. However, integrating traditional plasmonic materials like gold and silver into silicon-based platforms presents significant challenges, particularly due to their incompatibility with standard silicon processing techniques and their increased optical losses at longer wavelengths, which can hinder performance in near-infrared applications. Plasmonic devices, leveraging advances in device architectures, have the potential to close these performance gaps and enable the next generation of high-speed, on-chip data communication. This review explores recent progress in silicon-integrated hybrid-mode plasmonic devices, highlighting the potential of transparent conductive oxides like indium tin oxide for low-loss and tunable operation. Key device topologies including coupled hybrid plasmonic waveguides and dielectric-based heterostructures are examined, along with fabrication techniques and practical considerations. By critically comparing various plasmonic approaches and identifying their respective advantages and limitations, a path toward realizing the full potential of plasmonics in shaping the future of high-performance, silicon-based integrated photonics is charted.

physics.app-ph↗

arXiv2024

Error Free Quantum Target Finding: When Sequential Detection Meets High Dimensional Entanglement

We present a new method for target finding and ranging in Lidar applications using high-dimensional Bell states. Combined with a sequential decision rule, this scheme asymptotically achieves zero error probability with finite energy expenditure. This result stems from the synergy of high-dimensional entanglement suppressing false positives and the sequential decision rule optimizing energy usage. It effectively provides a pathway to unbounded quantum advantage over classical methods and has substantial implications for high-precision sensing in noisy environments.

quant-ph↗

arXiv2024

High-Dimensional Bell States: A Paradigm Shift for Quantum Illumination

This paper solves the open problem of characterizing the performance of quantum illumination (QI) with discrete variable states. By devising a novel quantum measurement approach along with meticulous analysis, our investigation demonstrates that, in the limit as $M \rightarrow \infty$, the maximally entangled $M$ mode Bell state achieves optimal performance, matching the two-mode squeezed vacuum in a high-noise regime and exceeding it in low-noise. This result challenges the dominance of continuous variable states in photonic sensing applications and extends the novelty of QI to regimes where no quantum advantage was believed to exist. A closer analysis reveals that this advantage stems from retained entanglement in the transmitted Bell state, a paradigm-shifting discovery since interaction with the environment in optical systems is believed to break entanglement. The complete mathematical analysis of this work provides granular insights into the interaction between photonic systems and environmental noise, motivating further research into discrete variable quantum sensing.

quant-ph↗

arXiv2024

A novel multi-photon entangled state with enhanced resilience to path loss

In the realm of quantum information, entanglement stands as a cornerstone phenomenon. It underpins a vast array of quantum information processes, offering significant potential for advancements in quantum computing, communication, and sensing. This paper introduces a novel multi-photon entangled state, which generalizes the maximally entangled single-photon state and exhibits remarkable resilience to signal attenuation in photonic applications. We demonstrate the novelty of the proposed state through a simplified target detection model and illustrate its superior performance over traditional single-photon protocols, attributed to its higher entanglement level and enhanced noise suppression capabilities. Our findings suggest that the proposed multi-photon state holds significant promise for enhancing the efficiency and reliability of photonic applications subject to loss. This work lays the groundwork for future exploration into the practical applications of multi-photon entangled states in quantum technologies, potentially revolutionizing our approach to quantum sensing and beyond

quant-ph↗

arXiv2022

Biphoton engineering using modal spatial overlap on-chip

Photon pairs generated by spontaneous parametric down-conversion are essential for optical quantum information processing, in which the quality of biphoton states is crucial for the performance. To engineer the biphoton wavefunction (BWF) on-chip, the pump envelope function and the phase matching function are commonly adjusted, while the modal field overlap has been considered as a constant in the frequency range of interest. In this work, by utilizing modal coupling in a system of coupled waveguides, we explore the modal field overlap as a new degree of freedom for biphoton engineering. We provide design examples for on-chip generations of polarization entangled photons and heralded single photons, respectively. This strategy can be applied to waveguides of different materials and structures, offering new possibilities for photonic quantum state engineering.

quant-ph↗

arXiv2022

Quantum and Non-local Effects Offer LiDAR over 40dB Advantage

Non-local effects have the potential to radically move forward quantum enhanced LiDAR to provide an advantage over classical LiDAR not only in laboratory environments but practical implementation. In this work, we demonstrate a 43dB lower signal-to-noise ratio using a quantum enhanced LiDAR based on time-frequency entanglement compared with a classical phase-insensitive LiDAR system. Our system can tolerate more than 3 orders of magnitude higher noise than classical singlephoton counting LiDAR systems before detector saturation. To achieve these advantages, we use non-local cancellation of dispersion to take advantage of the strong temporal correlations in photon pairs in spite of the orders of magnitude larger detector temporal uncertainty. We go on to incorporate this scheme with purpose-built scanning collection optics to image non-reflecting targets in an environment with noise.

quant-ph↗

arXiv2022

An Optical Parametric Amplifier via $ χ^{(2)} $ in AlGaAs Waveguides

We report parametric gain by utilizing $ χ^{(2)} $ non-linearities in a semiconductor Bragg Reflection Waveguide (BRW) waveguide chip. Under the two-mode degenerate type II phase matching, it can be shown that more than 18 dBs of parametric gain for both TE and TM modes is tenable in 100s of micrometers of device length. Polarization insensitive parametric gain can be attained within the 1550 nm region of the spectrum. These AlGaAs BRW waveguides exhibit sub-photon per pulse sensitivity. This is in sharp contrast to other types of parametric gain devices which utilize $ χ^{(3)} $, where the pump wavelength is in the vicinity of the signal wavelength. This sensitivity, which reached 0.1~photon/pulse, can usher a new era for on-chip quantum information processing using compact, micrometer-scale devices.

physics.optics↗

arXiv2021

Label-Free Spontaneous Raman Sensing in Photonic Crystal Fibers with Nanomolar Sensitivity

An approach to significantly enhance spontaneous Raman sensitivity through the formation of a thin film via thermophoresis along with evaporation at the facet of a Hollow-Core Photonic Crystal Fiber is reported for the first time. Sensitivity of detection is increased by more than 6 orders of magnitude for both organic and inorganic nanoparticles, facilitating the search for trace analytes in solution. Detection of two nanoparticles, Alumina and Polystyrene, is demonstrated down to 392 nM without the use of Surface-Enhanced Raman Spectroscopy or other chemical-based procedures. This new thin-film deposition approach simplifies the simultaneous detection and analysis of small trace compounds, a previously arduous task using conventional spontaneous Raman.

physics.optics↗

arXiv2021

Wavelength Conversion Efficiency Enhancement in Modal Phase Matched $χ^{(2)}$ Nonlinear Waveguides

Modal phase matching (MPM) is a widely used phase matching technique in Al$_x$Ga$_{1-x}$As and other $χ^{(2)}$ nonlinear waveguides for efficient wavelength conversions. The use of a non-fundamental spatial mode compensates the material dispersion but also reduces the spatial overlap of the three interacting waves and therefore limits the conversion efficiency. In this work, we develop a technique to increase the nonlinear overlap by modifying the material nonlinearity, instead of the traditional method of optimizing the modal field profiles. This could eliminate the limiting factor of low spatial overlap inherent to MPM and significantly enhance the conversion efficiency. Among the design examples provided, this technique could increase the conversion efficiency by a factor of up to $\sim$290 in an Al$_x$Ga$_{1-x}$As waveguide. We further show that this technique is applicable to all $χ^{(2)}$ material systems that utilize MPM for wavelength conversion.

physics.optics↗

arXiv2021

Spectrally pure photon pair generation in asymmetric heterogeneously coupled waveguides

In this work, we develop a design methodology to generate spectrally pure photon pairs in asymmetric heterogeneously coupled waveguides by spontaneous parametric down-conversion. Mode coupling in a system of waveguides is used to directly tailor the group velocity of a supermode to achieve group velocity matching (GVM) that is otherwise not allowed by material dispersion. Design examples based on thin film lithium niobate waveguides are provided, demonstrating high spectral purity and temperature tunability. This approach is a versatile strategy applicable to waveguides of different materials and structures, allowing more versatility in single-photon source designs.

physics.optics↗

arXiv2021

Integrated Photonic Functions Using Anisotropic 2D Material Structures

Plasmonic waveguides based on 2D materials, which enable the formations of guided modes confined around few-layered material, are promising plasmonic platforms for the miniaturization of photonic devices. Nonetheless, such waveguides support modes that are evanescent in the waveguide core with the majority of the fields concentrated around waveguide edges, which are different from those supported by 3D dielectric waveguides where the modal fields are of oscillatory nature and peak at the center. As a result, many photonic devices and functionalities that can be achieved within 3D dielectric waveguides based on total-internal-reflation modes cannot be realized using 2D material-based plasmonic structures. In this work, we propose and demonstrate how to leverage anisotropy in 2D materials to tailor of modal fields supported by 2D material waveguide for the first time. By regulating material absorption of the constituent 2D materials, the modal fields of these 2D modes can be tailored to localize around the waveguide center, which in turn can improve the efficiencies of coupling-based photonic functions using 2D materials, from in-plane multimode-interference couplers to out-of-plane optical radiation. Using natural anisotropic 2D materials such as black phosphorus, these pivotal functions can expand existing device capabilities that are typically achieved in 3D dielectrics but using 2D materials, thus allowing for the implementation of 2D plasmonic circuits with no need to relying on 3D layers.

physics.optics↗

arXiv2021

Field canalization using anisotropic 2D plasmonics

Optical devices capable of suppressing diffraction nature of light are of great technological importance to many nanophotonic applications. One important technique to achieve diffractionless optics is to exploit field canalization effect. However, current technological platforms based on metamaterial structures typically suffer from strict loss-confinement tradeoff, or lack dynamic reconfigurability over device operations. Here we report an integrated canalization platform that can alleviate this performance tradeoff. It is found that by leveraging material absorption of anisotropic 2D materials, the dispersion of this class of materials can flatten without increasing propagation losses and compromising confinement. The realization of such plasmon canalization can be considered using black phosphorus (BP), where topological transition from elliptic to hyperbolic curves can be induced by dynamically leveraging material absorption of BP. At the transition point, BP film can support long range, deeply subwavelength, near-diffractionless field propagation, exhibiting diffraction angle of 5.5o, propagation distance of 10λspp, and λspp < λ0/300.

physics.optics↗

arXiv2021

Enhanced Sensitivity for Quantifying Disease Markers via Raman and Machine-Learning of Circulating Biofluids in Optofluidic Chips

We demonstrate novel instrumentation for spontaneous Raman spectroscopy in biofluids, enabling development of a portable, automated, reliable diagnostics technique requiring minimal operator expertise to quantify disease markers. Label-free Raman analysis of biofluids at physiologically-relevant sensitivities is achieved using a microfluidic-embedded liquid-core-waveguide augmented with a unique circulation approach: thermal damage and spectrum variance is minimized, eliminating conventional limits on integration time for excellent signal-to-noise ratio and temporal stability. Machine-learning then optimizes spectrum processing, yielding quantitative results independent of end-user proficiency. Sub-mM accuracy is achieved in solutions of both high and low turbidity, surpassing the sensitivity of previous techniques for analytes with a small scattering cross-section, such as glucose. We attain a new record for label-free glucose measurements in an artificial whole-blood, achieving an accuracy up to 0.14 mM, well-exceeding the 0.78 mM accuracy required for diabetic monitoring, establishing our technique's potential to significantly facilitate portable Raman for complex biofluid analysis.

physics.bio-ph↗

arXiv2021

Laser Cooling of Germanium Semiconductor Nanocrystals

Laser cooling of matter through anti-Stokes photoluminescence, where the emitted frequency of light exceeds that of the impinging laser by virtue of absorption of thermal vibrational energy, has been successfully realized in condensed media, and in particular with rare earth doped systems achieving sub-100K solid state optical refrigeration. Studies suggest that laser cooling in semiconductors has the potential of achieving temperatures down to ~10K and that its direct integration can usher unique high-performance nanostructured semiconductor devices. While laser cooling of nanostructured II-VI semiconductors has been reported recently, laser cooling of indirect bandgap semiconductors such as group IV silicon and germanium remains a major challenge. Here we report on the anomalous observation of dominant anti-Stokes photoluminescence in germanium nanocrystals. We attribute this result to the confluence of ultra-high purity nanocrystal germanium, generation of high density of electron-hole plasma, the inherent degeneracy of longitudinal and transverse optical phonons in non-polar indirect bandgap semiconductors, and commensurate spatial confinement effects. At high laser intensities, laser cooling with lattice temperature as low as ~50K is inferred.

cond-mat.mes-hall↗

arXiv2020

Supermode hybridization: a material-independent route towards record Schottky detection sensitivity using <0.05 μm3 amorphous absorber volume

Schottky photodetectors are attractive for CMOS-compatible photonic integrated circuits, but the trade-off between photon absorption and hot carrier emission often compromises the detection fidelity and sensitivity. Here, we report a hybridization-based waveguiding effect that can improve the sensitivity of guided-wave Schottky detection by >200x. By hybridizing the supermodes guided by asymmetrical coupled plasmonic nanostructures, light-matter-interaction can be significantly enhanced even if the thickness of the light absorbing region is only a few nanometers, thus allowing the absorption and emission efficiencies to be simultaneously optimized for the first time. Using amorphous-based active junction with absorbing volume of only 0.031 μm3, our detectors demonstrate record experimental sensitivity of -55 dBm, approaching that of crystalline-based Ge counterparts with >36x larger absorption region. The ability to maximize field overlap within small device volume and improve photodetection fidelity without using crystalline materials pave the way towards improved back-end-of-line interconnection, single photon detection, and 2D optoelectronics.

physics.optics↗

arXiv2020

Joint measurement of time-frequency entanglement via sum frequency generation

We propose, analyze, and evaluate a technique for the joint measurement of time-frequency entanglement between two photons. In particular, we show that the frequency sum and time difference of two photons could be simultaneously measured through the sum-frequency generation process, without measuring the time or frequency of each individual photon. We demonstrate the usefulness of this technique by using it to design a time-frequency entanglement based continuous variable superdense coding and a quantum illumination protocol. Performance analysis of these two protocols suggests that the joint measurement of strong time-frequency entanglement of non-classical photon pairs can significantly enhance the performance of joint-measurement based quantum communication and metrology protocols.

quant-ph↗

arXiv2020

Enhancing classical target detection performance using nonclassical Light

In this article, we demonstrate theoretically and experimentally how one can exploit correlations generated in monolithic semiconductor quantum light sources to enhance the performance of optical target detection. A prototype target detection protocol, the quantum time-correlation (QTC) detection protocol, with spontaneous parametric down-converted photon-pair sources, is discussed. The QTC protocol only requires time-resolved photon-counting detection, which is phase-insensitive and therefore suitable for optical target detection. As a comparison to the QTC detection protocol, we also consider a classical phase-insensitive target detection protocol based on intensity detection. We formulated the target detection problem as a probe light transmission estimation problem, and we quantify the target detection performance with the Fisher information criterion and the receiver operation characteristic analysis. Unlike classical target detection and ranging protocols, the probe photons in our QTC detection protocol are completely indistinguishable from the background noise and therefore useful for covert ranging applications. Finally, our technological platform is highly scalable and tunable and thus amenable to large scale integration necessary for practical applications.

physics.optics↗