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Lipson, Michal

Publications and source records attributed to Lipson, Michal.

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

N -way parametric frequency beamsplitter for quantum photonics

Optical networks are the leading platform for the transfer of information due to their low loss and ability to scale to many information channels using optical frequency modes. To fully leverage the quantum properties of light in this platform, it is desired to manipulate higher-dimensional superpositions by orchestrating linear, beamsplitter-type interactions between several channels simultaneously. We propose a method of achieving simultaneous, all-to-all coupling between N optical frequency modes via N -way Bragg-scattering four-wave mixing. By exploiting the frequency degree of freedom, additional modes can be multiplexed in an interaction medium of fixed volume and loss while avoiding the introduction of excess noise. We generalize the theory of the frequency-encoded two-mode interaction to N modes under this four-wave-mixing approach, finding that arbitrary unitary transformations are possible through successive four-wave-mixing pump configurations. We experimentally verify the quantum nature of this scheme by demonstrating three-way multiphoton interference. Two input photons are shared among three frequency modes and display interference differing from that of two classical (coherent-state) inputs. These results show the potential of our approach for the scalability of photonic quantum information processing to general N -mode systems in the frequency domain. Published by the American Physical Society 2025

Oliver, Richard (ORCID:0000000207760657)↗
DOE OSTI2025

Automated tuning of a ring-assisted MZI-based interleaver for Kerr frequency combs

We demonstrate a compact ring-assisted Mach–Zehnder interferometer (RAMZI)-based silicon photonic interleaver with a 400 GHz free spectral range (FSR), featuring flat passbands exceeding a spectral range of 50 nm. Additionally, we introduce a novel, to the best of our knowledge, add-on structure and tuning method enabling automated compensation for fabrication imperfections, precise shaping of the RAMZI flat-top passbands, and alignment with Kerr comb lines. Experimental results have shown successful interleaving of eight channels of distributed-feedback (DFB) lasers as well as a 200 GHz Kerr comb, both achieving an extinction ratio of approximately 20 dB.

Wang, Songli (ORCID:0009000626380795)↗
DOE OSTI2024

High power chip-scale laser

The lack of high-power integrated lasers has been limiting silicon photonics. Despite much progress in chip-scale laser integration, power output remains below levels required for key applications due to low energy efficiency at high pumping currents. Here we break this power limitation by coupling a broad-area multimode gain chip to a silicon-nitride ring resonator and single-mode filter. The resulting optical feedback causes the multimode-gain chip to concentrate its power into a single highly coherent mode. Our device produces more than 150 mW of power and 400 kHz linewidth. We achieve these metrics while maintaining a small footprint of 3 mm 2 .

Antman, Yair↗
DOE OSTI2024

Clearing a path for light through non-Hermitian media

Abstract The performance of all active photonic devices today is greatly limited by loss. Here, we show that one can engineer a low loss path in a metal-clad lossy multi-mode waveguide while simultaneously achieving high-performance active photonic devices. We leverage non-Hermitian systems operating beyond the exceptional point to enable the redistribution of losses in a multi-mode photonic waveguide. Consequently, our multi-mode waveguide offers low propagation losses for fundamental mode while other higher order modes experience prohibitively high losses. Furthermore, we show an application of this non-Hermitian waveguide platform in designing power-efficient thermo-optic phase shifters with significantly faster response times than conventional silicon-based thermo-optic phase shifters. Our device achieves a propagation loss of less than 0.02 dB μm −1 for our non-Hermitian waveguide-based phase shifters with high performance efficiency of P π ⋅ τ = 19.1 mW μs. In addition, our phase shifters have significantly faster response time (rise/fall time), τ ≈ 1.4 μs, compared to traditional silicon based thermo-optic phase shifters.

Materials Science↗
DOE OSTI2024

Efficient excitation and control of integrated photonic circuits with virtual critical coupling

Critical coupling in integrated photonic devices enables the efficient transfer of energy from a waveguide to a resonator, a key operation for many applications. This condition is achieved when the resonator loss rate is equal to the coupling rate to the bus waveguide. Carefully matching these quantities is challenging in practice, due to variations in the resonator properties resulting from fabrication and external conditions. Here, we demonstrate that efficient energy transfer to a non-critically coupled resonator can be achieved by tailoring the excitation signal in time. We rely on excitations oscillating at complex frequencies to load an otherwise overcoupled resonator, demonstrating that a virtual critical coupling condition is achieved if the imaginary part of the complex frequency equals the mismatch between loss and coupling rate. We probe a microring resonator with tailored pulses and observe a minimum intensity transmission T = 0.11 in contrast to a continuous-wave transmission T = 0.58, corresponding to 8 times enhancement of intracavity intensity. Our technique opens opportunities for enhancing and controlling on-demand light-matter interactions for linear and nonlinear photonic platforms.

42 ENGINEERING↗
DOE OSTI2024

Absorption and scattering limits of silicon nitride integrated photonics in the visible spectrum

Visible-light photonic integrated circuits (PICs) promise scalability for technologies such as quantum information, biosensing, and scanning displays, yet extending large-scale silicon photonics to shorter wavelengths has been challenging due to the higher losses. Silicon nitride (SiN) has stood out as the leading platform for visible photonics, but the propagation losses strongly depend on the film’s deposition and fabrication processes. Current loss measurement techniques cannot accurately distinguish between absorption and surface scattering, making it difficult to identify the dominant loss source and reach the platform’s fundamental limit. Here we demonstrate an ultra-low loss, high-confinement SiN platform that approaches the limits of absorption and scattering across the visible spectrum. Leveraging the sensitivity of microresonators to loss, we probe and discriminate each loss contribution with unparalleled sensitivity, and derive their fundamental limits and scaling laws as a function of wavelength, film properties and waveguide parameters. Through the design of the waveguide cross-section, we show how to approach the absorption limit of the platform, and demonstrate the lowest propagation losses in high-confinement SiN to date across the visible spectrum. We envision that our techniques for loss characterization and minimization will contribute to the development of large-scale, dense PICs that redefine the loss limits of integrated platforms across the electromagnetic spectrum.

Corato-Zanarella, Mateus (ORCID:0000000327318046)↗
DOE OSTI2024

2D material platform for overcoming the amplitude–phase tradeoff in ring resonators

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., Δ n Δ k ∼1. To implement this strategy, we demonstrate an active hybrid platform that combines a low-loss SiN ring resonator with 2D materials such as graphene and transition metal dichalcogenide [tungsten disulphide (WSe 2 )], which induces a strong change in the imaginary and real parts of the index. Our platform consisting of a 25 µm long Gr-Al 2 O 3 -WSe 2 capacitor embedded on a SiN ring of 50 µm radius (∼8% ring coverage) achieves a continuous phase shift of (0.46±0.05) π radians with an insertion loss (IL) of 3.18±0.20 dB and a transmission modulation (Δ T Ring ) of 1.72±0.15dB at a probe wavelength ( λ p ) of 1646.18 nm. We find that our Gr-Al 2 O 3 -WSe 2 capacitor exhibits a phase modulation efficiency ( V π 2 ⋅ L ) of 0.530±0.016V⋅cm and can support an electro-optic bandwidth of 14.9±0.1GHz. We further show that our platform can achieve a phase shift of π radians with an IL of 5 dB and a minimum Δ T of 0.046 dB. We demonstrate the broadband nature of the binary phase response, by measuring a phase shift of (1.00±0.10) π radians, with an IL of 5.20±0.31dB and a minimal Δ T Ring of 0.015±0.006dB for resonances spanning from 1564 to 1650 nm. This SiN–2D hybrid platform provides the design for compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

Datta, Ipshita (ORCID:0000000318842882)↗
DOE OSTI2023

Chip-scale frequency combs for data communications in computing systems

Recent developments in chip-based frequency-comb technology demonstrate that comb devices can be implemented in applications where photonic integration and power efficiency are required. The large number of equally spaced comb lines that are generated make combs ideal for use in communication systems, where each line can serve as an optical carrier to allow for massively parallel wavelength-division multiplexing (WDM) transmission. In this review, we summarize the developments in integrated frequency-comb technology for use as a WDM source for communication systems in data centers and high-performance computing systems. We highlight the following three approaches for chip-scale comb generation: semiconductor modelocked lasers, electro-optic combs, and Kerr frequency combs.

Okawachi, Yoshitomo (ORCID:0000000196390549)↗
DOE OSTI2023

Coherent Combining for High‐Power Kerr Combs

Abstract Kerr frequency combs enable the miniaturization of comb sources for applications such as data communications and spectroscopy. However, due to the high field confinement and effective nonlinearity, Kerr combs typically operate with low output comb powers. While nonsolitonic Kerr combs operating in the normal group velocity dispersion (GVD) regime can access high pump‐to‐comb conversion efficiencies and relatively flat spectral profiles, many frequency comb applications require even higher comb‐line powers that are otherwise fundamentally unattainable without the use of optical amplifiers. A high efficient coherent beam combining of Kerr combs is demonstrated via on‐chip synchronization to greatly enhanced comb‐line powers. Two normal GVD Kerr combs are coherently combined for a 2.9 dB increase in comb power compared to a single comb while maintaining a high total pump‐to‐comb conversion efficiency of 26%. Lastly, it is shown that via spectral engineering of two normal GVD combs, it should be possible to significantly increase the spectral flatness of a combined comb. This platform enables fully integrated systems with powers that can readily exceed that of an individual comb system by more than an order of magnitude.

Kim, Bok Young↗
DOE OSTI2023

Ultra‐Low‐Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries

Abstract The fabrication processes of silicon nitride (Si 3 N 4 ) photonic devices used in foundries require low temperature deposition, which typically leads to high propagation losses. Here, it is shown that propagation loss as low as 0.42 dB cm −1 can be achieved using foundry compatible processes by solely reducing waveguide surface roughness. By postprocessing the fabricated devices using rapid thermal anneal (RTA) and furnace anneal, propagation losses down to 0.28 dB cm −1 and 0.06 dB cm −1 , respectively, are achieved. These low losses are comparable to the conventional devices using high temperature, high‐stress LPCVD films. The dispersion of the devices is also tuned, and it is proved that these devices can be used for linear and nonlinear applications. Low threshold parametric oscillation, broadband frequency combs, and narrow‐linewidth laser are demonstrated. This work demonstrates the feasibility of scalable photonic systems based on foundries.

Ji, Xingchen↗
DOE OSTI2023

Fabrication-robust silicon photonic devices in standard sub-micron silicon-on-insulator processes

Perturbations to the effective refractive index from nanometer-scale fabrication variations in waveguide geometry plague high index-contrast photonic platforms; this includes the ubiquitous sub-micron silicon-on-insulator (SOI) process. Such variations are particularly troublesome for phase-sensitive devices, such as interferometers and resonators, which exhibit drastic changes in performance as a result of these fabrication-induced phase errors. In this Letter, we propose and experimentally demonstrate a design methodology for dramatically reducing device sensitivity to silicon width variations. We apply this methodology to a highly phase-sensitive device, the ring-assisted Mach–Zehnder interferometer (RAMZI), and show comparable performance and footprint to state-of-the-art devices, while substantially reducing stochastic phase errors from etch variations. This decrease in sensitivity is directly realized as energy savings by significantly reducing the required corrective thermal tuning power, providing a promising path toward ultra-energy-efficient large-scale silicon photonic circuits.

Rizzo, Anthony (ORCID:000000034752797X)↗
DOE OSTI2022

Electro-refractive modulation in photonic structures

Methods, systems, and devices are described for electro-optic tuning. An example device may comprise a first layer comprising a transition metal di-chalcogenide material, a second layer comprising a conductive material, and a third layer comprising a dielectric material. The third layer may be disposed at least partially between the first layer and the second layer. An electrical potential difference applied between the first layer and the second layer may cause a tunable refractive index change in the first layer.

Lipson, Michal↗
DOE OSTI2021

Synchronization of nonsolitonic Kerr combs

Synchronization is a ubiquitous phenomenon in nature that manifests as the spectral or temporal locking of coupled nonlinear oscillators. In the field of photonics, synchronization has been implemented in various laser and oscillator systems, enabling applications including coherent beam combining and high-precision pump-probe measurements. Recent experiments have also shown time-domain synchronization of Kerr frequency combs via coupling of two separate oscillators operating in the dissipative soliton [i.e., anomalous group velocity dispersion (GVD)] regime. Here, we demonstrate all-optical synchronization of Kerr combs in the nonsolitonic, normal GVD regime in which phase-locked combs with high pump-to-comb conversion efficiencies and relatively flat spectral profiles are generated. Our results reveal the universality of Kerr comb synchronization and extend its scope beyond the soliton regime, opening a promising path toward coherently combined normal GVD Kerr combs with spectrally flat profiles and high comb-line powers in an efficient microresonator platform.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Conversion efficiency of soliton Kerr combs

We investigate the conversion efficiency (CE) of soliton modelocked Kerr frequency combs. Our analysis reveals three distinct scaling regimes of CE with the cavity free spectral range (FSR), which depends on the relative contributions of the coupling and propagation loss to the total cavity loss. Our measurements, for the case of critical coupling, verify our theoretical prediction over a range of FSRs and pump powers. Our numerical simulations also indicate that mode crossings have an adverse effect on the achievable CE. Our results indicate that microresonator combs operating with spacings in the electronically detectable regime are highly inefficient, which could have implications for integrated Kerr comb devices.

Jang, Jae K. (ORCID:0000000187786058)↗
DOE OSTI2020

PINE: Photonic Integrated Networked Energy efficient datacenters

We review the motivation, goals, and achievements of the Photonic Integrated Networked Energy efficient datacenter (PINE) project, which is part of the Advanced Research Projects Agency–Energy (ARPA-E) ENergy-efficient Light-wave Integrated Technology Enabling Networks that Enhance Dataprocessing (ENLITENED) program. Here, the PINE program leverages the unique features of photonic technologies to enable alternative mega-datacenters and high-performance computing (HPC) system architectures that deliver more substantial energy efficiency improvements than can be achieved through link energy efficiency alone. In phase 1 of the program, the PINE system architecture demonstrated an average factor of 2.2× improvement in transactions/joule across a diverse set of HPC and datacenter applications. In phase 2, PINE will demonstrate an aggressive 1.0 pJ/bit total link budget with high-bandwidth-density dense wavelength-division multiplexing (DWDM) links to enable additional 2.5× or more efficiency gains through deep resource disaggregation.

42 ENGINEERING↗
DOE OSTI2020

Femtosecond exciton dynamics in WSe 2 optical waveguides

Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe 2 , prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the optical constants following femtosecond photoexcitation. By monitoring the phase velocity of the waveguide modes, we detect incoherent A-exciton bleaching along with a coherent optical Stark shift in WSe 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗