arXiv subjects

Michal Lipson

Publications and source records attributed to Michal Lipson.

At least 19 recordsLinked to original sources

arXiv2026

Kerr Soliton Generation in Ultra-Compact Photonic Devices

Chip-based nonlinear photonics offer the capability to integrate devices with all the requisite photonic components (e.g., filters, couplers, detectors) into highly compact form factors. This offers the possibility of making the devices scalable, robust, and manufacturable. Such integrated photonic devices will enable applications in optical communications, precision metrology, microwave generation, and LIDAR. However, thermal instabilities represent a major hurdle in the deterministic operation of nonlinear optical processes in such integrated resonant structures such as microresonators. In this work we demonstrate deterministic and highly stable Kerr soliton comb generation in tight-spiral microresonators with comb spacings as low as 16 GHz. We perform a comprehensive experimentally-validated thermal model of such compact microresonators and reveal non-trivial thermally-driven instabilities governing the cavity soliton dynamics. We design and implement a fast feedback loop on the devices to overcome thermal perturbations and stabilize cavity-soliton states, including those that are otherwise unstable, and to allow for controlled transitions between the soliton states. Our approach enables the realization of thermally-stable highly compact soliton microcomb devices in a wide variety of photonic platforms.

physics.optics↗

arXiv2025

Frequency-stable nanophotonic microcavities via integrated thermometry

Field-deployable integrated photonic devices co-packaged with electronics will enable important applications such as optical interconnects, quantum information processing, precision measurements, spectroscopy, and microwave generation. Significant progress has been made over the past two decades on increasing the functional complexity of photonic chips. However, a critical challenge that remains is the lack of scalable techniques to overcome thermal perturbations arising from the environment and co-packaged electronics. Here, we demonstrate a fully integrated scheme to monitor and stabilize the temperature of a high-Q microresonator on a Si-based chip, which can serve as a photonic frequency reference. Our approach relies on a thin-film metallic resistor placed directly above the microcavity, acting as an integrated resistance thermometer, enabling unique mapping of the cavity's absolute resonance wavelength to the thermometer's electrical resistance. Following a one-time calibration, the microresonator can be accurately and repeatably tuned to any desired absolute resonance wavelength using thermometry alone with a root-mean squared wavelength error of <0.8 pm over a timespan of days. We frequency-lock a distributed feedback (DFB) laser to the microresonator and demonstrate a 48x reduction in its frequency drift, resulting in its center wavelength staying within +-0.5 pm of the mean over the duration of 50 hours in the presence of significant ambient fluctuations, outperforming many commercial DFB and wavelength-locker-based laser systems. Finally, we stabilize a soliton mode-locked Kerr comb without the need for photodetection, paving the way for Kerr-comb-based photonic devices that can potentially operate in the desired mode-locked state indefinitely.

physics.optics↗

arXiv2025

Telecom-to-Visible Quantum Frequency Converter on a Silicon Nitride Chip

Quantum frequency conversion serves a key role in the realization of hybrid quantum networks by interfacing between wavelength-incompatible platforms. Here we present the first quantum frequency converter connecting visible and telecom domains on a silicon nitride (SiN) chip, using Bragg-scattering four-wave mixing to upconvert heralded single photons from 1260 to 698 nm, which covers a 192 THz span. We examine the noise sources in SiN and devise approaches to suppress noise photons at the source and target frequencies to enable measurements at the single-photon level. We demonstrate an on-chip conversion efficiency of 5% in photon flux and describe design modifications that can be implemented to significantly improve it. Our results pave the way for the implementation of CMOS-compatible devices in quantum networks.

quant-ph↗

arXiv2025

Quantum State Tomography in a Third-Order Integrated Optical Parametric Oscillator

We measured the covariance matrix of the fields generated in an integrated third-order optical parametric oscillator operating above threshold. We observed up to $(2.3 \pm 0.3)$ dB of squeezing in amplitude difference, inferred $(4.9 \pm 0.7)$ dB of on-chip squeezing, while an excess of noise for the sum of conjugated quadratures hinders the entanglement. The degradation of amplitude correlations and state purity for the increasing of the pump power is consistent with the observed growth of the phase noise of the fields, showing the necessity of strategies for phase noise control aiming at entanglement generation in these systems.

quant-ph↗

arXiv2024

Nonlinear Dynamics of Coupled-Resonator Kerr-Combs

The nonlinear interaction of a microresonator pumped by a laser has revealed complex dynamics including soliton formation and chaos. Initial studies of coupled-resonator systems reveal even more complicated dynamics that can lead to deterministic modelocking and efficient comb generation. Here we perform theoretical analysis and experiments that provide insight into the dynamical behavior of coupled-resonator systems operating in the normal group-velocity-dispersion regime. Our stability analysis and simulations reveal that the strong mode-coupling regime, which gives rise to spectrally-broad comb states, can lead to an instability mechanism in the auxiliary resonator that destabilizes the comb state and prevents mode-locking. We find that this instability can be suppressed by introducing loss in the auxiliary resonator. We investigate the stability of both single- and multi-pulse solutions and verify our theoretical predictions by performing experiments in a silicon-nitride platform. Our results provide an understanding for accessing broad, efficient, relatively flat high-power mode-locked combs for numerous applications in spectroscopy, time-frequency metrology, and data communications.

physics.optics↗

arXiv2024

Overcoming stress limitations in SiN nonlinear photonics via a bilayer waveguide

Silicon nitride (SiN) formed via low pressure chemical vapor deposition (LPCVD) is an ideal material platform for on-chip nonlinear photonics owing to its low propagation loss and competitive nonlinear index. Despite this, LPCVD SiN is restricted in its scalability due to the film stress when high thicknesses, required for nonlinear dispersion engineering, are deposited. This stress in turn leads to film cracking and makes integrating such films in silicon foundries challenging. To overcome this limitation, we propose a bilayer waveguide scheme comprised of a thin LPCVD SiN layer underneath a low-stress and low-index PECVD SiN layer. We show group velocity dispersion tuning at 1550nm without concern for filmcracking while enabling low loss resonators with intrinsic quality factors above 1 million. Finally, we demonstrate a locked, normal dispersion Kerr frequency comb with our bilayer waveguide resonators spanning 120nm in the c-band with an on-chip pump power of 350mW.

physics.optics↗

arXiv2024

N-Way 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, 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 and experimentally verify the quantum nature of this scheme by demonstrating three-way multiphoton interference. The 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.

quant-ph↗

arXiv2023

All-optical frequency division on-chip using a single laser

The generation of spectrally pure high-frequency microwave signals is a critical functionality in fundamental and applied sciences, including metrology and communications. The development of optical frequency combs has enabled the powerful technique of optical frequency division (OFD) to produce microwave oscillations of the highest quality. The approaches for OFD demonstrated to date demand multiple lasers with space- and energy-consuming optical stabilization and electronic feedback components, resulting in device footprints incompatible with integration into a compact and robust photonic platform. Here, we demonstrate all-optical OFD on a single photonic chip driven with a single continuous-wave laser. We generate a dual-point frequency reference using the beat frequency of the signal and idler fields from a microresonator-based optical parametric oscillator (OPO), which achieves high phase stability due to the inherently strong signal-idler frequency correlations. We implement OFD by optically injecting the signal and idler fields from the OPO to a Kerr-comb microresonator on the same chip. We show that the two distinct dynamical states of Kerr cavities can be passively synchronized, allowing broadband frequency locking of the comb state, which transfers the stability of the OPO frequencies to the repetition rate of the Kerr comb. A 630-fold phase-noise reduction is observed when the Kerr comb is synchronized to the OPO, which represents the lowest noise generated on the silicon-nitride platform. Our work demonstrates a simple, effective approach for performing OFD and provides a pathway toward chip-scale devices that can generate microwave frequencies comparable to the purest tones produced in metrological laboratories. This technology can significantly boost the further development of data communications and microwave sensing.

physics.optics↗

arXiv2023

Large regenerative parametric amplification on chip at ultra-low pump powers

Chip-based optical amplifiers can significantly expand the functionalities of photonic devices. In particular, optical-parametric amplifiers (OPAs), with engineerable gain-spectra, are well-suited for nonlinear-photonic applications. Chip-based OPAs typically require long waveguides that occupy a large footprint, and high pump powers that cannot be easily produced with chip-scale lasers. We theoretically and experimentally demonstrate a microresonator-assisted regenerative OPA that benefits from the large nonlinearity enhancement of microresonators and yields a high gain in a small footprint. We achieve 30-dB parametric gain with only 9 mW of cw-pump power and show that the gain spectrum can be engineered to cover telecom channels inaccessible with Er-based amplifiers. We further demonstrate the amplification of Kerr-soliton comb lines and the preservation of their phase properties. Additionally, we demonstrate amplification by injection locking of optical-parametric oscillators, which corresponds to a regenerative amplifier pumped above the oscillation threshold. Novel dispersion engineering techniques such as coupled cavities and higher-order-dispersion phase matching can further extend the tunability and spectral coverage of our amplification schemes. The combination of high gain, small footprint, low pump power, and flexible gain-spectra engineering of our regenerative OPA is ideal for amplifying signals from the nanowatt to microwatt regimes for portable or space-based devices where ultralow electrical power levels are required and can lead to important applications in on-chip optical- and microwave-frequency synthesis and precise timekeeping.

physics.optics↗

arXiv2023

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

The fabrication processes of silicon nitride photonic devices used in foundries require low temperature deposition, which typically leads to high propagation losses. Here, we show that propagation loss as low as 0.42 dB/cm can be achieved using foundry compatible processes by solely reducing waveguide surface roughness. By post-processing the fabricated devices using rapid thermal anneal (RTA) and furnace anneal, we achieve propagation losses down to 0.28 dB/cm and 0.06 dB/cm, respectively. These low losses are comparable to the conventional devices using high temperature, high-stress low-pressure chemical vapor deposition (LPCVD) films. We also tune the dispersion of the devices, and 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. Our work demonstrates the feasibility of scalable photonic systems based on foundries.

physics.optics↗

arXiv2022

2D material platform for overcoming the amplitude-phase tradeoff in ring modulators

Compact, high-speed electro-optic phase modulators play a vital role in various large-scale applications including phased arrays, quantum and neural networks, and optical communication links. Conventional phase modulators 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 have been limited due to the high insertion loss associated with the phase change. Here, we show that high-finesse resonators can achieve a strong phase change with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent i.e. $\frac{Δn}{Δk} \sim 1$. To implement this strategy, we utilize a hybrid platform that combines a low-loss SiN ring resonator with electro-absorptive graphene (Gr) and electro-refractive WSe$_2$. We achieve a phase modulation efficiency ($V_{\fracπ{2}} \cdot L_{\fracπ{2}}$) of 0.045 V $\cdot$ cm with an insertion loss (IL$_{\fracπ{2}}$) of 4.7 dB for a phase change of $\fracπ{2}$ radians, in a 25 $μ$m long Gr-Al$_2$O$_3$-WSe$_2$ capacitor embedded on a SiN ring of 50 $μ$m radius. We find that our Gr-Al$_2$O$_3$-WSe$_2$ capacitor can support an electro-optic bandwidth of 14.9 $\pm$ 0.1 GHz. We further show that the $V_{\fracπ{2}} \cdot L_{\fracπ{2}}$ of our SiN-2D platform is at least an order of magnitude lower than that of electro-optic phase modulators based on silicon, III-V on silicon, graphene on silicon and lithium niobate. This SiN-2D hybrid platform provides the impetus to design compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

physics.optics↗

arXiv2022

High Power on-chip Integrated Laser

The lack of high power integrated lasers have been limiting silicon photonics. Despite much progress made in chip-scale laser integration, power remains below the level required for key applications. The main inhibiting factor for high power is the low energy efficiency at high pumping currents, dictated by the small size of the active device. Here we break this power limitation by demonstrating a platform that relies on the coupling of a broad-area multimode gain to a silicon-nitride feedback chip, which acts as an external cavity. The feedback provided by the silicon-nitride chip is routed through a ring resonator and a single-mode filter, thus causing the otherwise 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 high-performance metrics while maintaining a small footprint of 3 mm^2.

physics.optics↗

arXiv2022

Measurements and modeling of atomic-scale sidewall roughness and losses in integrated photonic devices

Atomic-level imperfections play an increasingly critical role in nanophotonic device performance. However, it remains challenging to accurately characterize the sidewall roughness with sub-nanometer resolution and directly correlate this roughness with device performance. We have developed a method that allows us to measure the sidewall roughness of waveguides made of any material (including dielectrics) using the high resolution of atomic force microscopy. We illustrate this method by measuring state-of-the-art photonic devices made of silicon nitride. We compare the roughness of devices fabricated using both DUV photo-lithography and electron-beam lithography for two different etch processes. To correlate roughness with device performance we describe what we call a new Payne-Lacey Bending model, which adds a correction factor to the widely used Payne-Lacey model so that losses in resonators and waveguides with bends can be accurately predicted given the sidewall roughness, waveguide width and bending radii. Having a better way to measure roughness and use it to predict device performance can allow researchers and engineers to optimize fabrication for state-of-the-art photonics using many materials.

physics.optics↗

arXiv2022

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 including 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 lowering the required corrective thermal tuning power, providing a promising path towards ultra-energy-efficient large-scale silicon photonic circuits.

physics.optics↗

arXiv2021

Optomechanical Synchronization across Multi-Octaves Frequency Spans

Experimental exploration of synchronization in scalable oscillator micro systems has unfolded a deeper understanding of networks, collective phenomena, and signal processing. Cavity optomechanical devices have played an important role in this scenario, with the perspective of bridging optical and radio frequencies through nonlinear classical and quantum synchronization concepts. In its simplest form, synchronization occurs when an oscillator is entrained by a signal with frequency nearby the oscillator's tone, and becomes increasingly challenging as their frequency detuning increases. Here, we experimentally demonstrate entrainment of a silicon-nitride optomechanical oscillator driven up to the fourth harmonic of its 32 MHz fundamental frequency. Exploring this effect, we also experimentally demonstrate for the first time a purely optomechanical RF frequency divider, where we performed frequency division up to a 4:1 ratio, i.e., from 128 MHz to 32 MHz. Further developments could harness these effects towards frequency synthesizers, phase-sensitive amplification and nonlinear sensing.

physics.optics↗

arXiv2021

Widely tunable and narrow linewidth chip-scale lasers from deep visible to near-IR

Widely-tunable and narrow-linewidth integrated lasers across all visible wavelengths are necessary to enable on-chip technologies such as quantum photonics, optical trapping, and biophotonics. However, such lasers have not been realized due to the strong wavelength sensitivity and high loss of integrated optical devices at short wavelengths. Here we overcome these challenges and demonstrate a chip-scale visible lasers platform by using tightly-confined, micrometer-scale silicon nitride resonators and commercial Fabry-Perot laser diodes. We achieve tunable and narrow-linewidth lasing in the deep blue (450 nm), blue (488 nm), green (520 nm), red (660 nm) and near-IR (785 nm) with coarse tuning up to 12 nm, fine tuning up to 33.9 GHz, linewidth down to sub-kHz, side-mode suppression ratio > 35 dB, and fiber-coupled power up to 10 mW. These specifications of our chip-scale lasers are comparable to those of state-of-the-art commercial laser systems, making them stand out as powerful tools for the next generation of visible-light technologies.

physics.optics↗

arXiv2021

Integrated Kerr frequency comb-driven silicon photonic transmitter

The exponential growth of computing needs for artificial intelligence and machine learning has had a dramatic impact on data centre energy consumption, which has risen to environmentally significant levels. Using light to send information between compute nodes can dramatically decrease this energy consumption while simultaneously increasing bandwidth. Through wavelength-division multiplexing with chip-based microresonator Kerr frequency combs, independent information channels can be encoded onto many distinct colours of light in the same optical fibre for massively parallel data transmission with low energy. While previous demonstrations have relied on benchtop equipment for filtering and modulating Kerr comb wavelength channels, data centre interconnects require a compact on-chip form factor for these operations. Here, we demonstrate the first integrated silicon photonic transmitter using a Kerr comb source. The demonstrated architecture is scalable to hundreds of wavelength channels, enabling a fundamentally new class of massively parallel terabit-scale optical interconnects for future green hyperscale data centres.

physics.app-ph↗

arXiv2021

Tunable narrow linewidth chip-scale mid-IR laser

Portable mid-infrared (mid-IR) spectroscopy and sensing applications require widely tunable, narrow linewidth, chip-scale, single-mode sources without sacrificing significant output power. However, no such lasers have been demonstrated beyond 3 $μ$m due to the challenge of building tunable, high quality-factor (Q) on-chip cavities. We demonstrate a tunable, single-mode mid-IR laser at 3.4 $μ$m using a high-Q silicon microring cavity with integrated heaters and a multi-mode Interband Cascade Laser (ICL). We show that the multiple longitudinal modes of an ICL collapse into a single frequency via self-injection locking with an output power of 0.4 mW and achieve an oxide-clad high confinement waveguide microresonator with a loaded Q of $2.8\times 10^5$. Using integrated microheaters, our laser exhibits a wide tuning range of 54 nm at 3.4 $μ$m with 3 dB output power variation. We further measure an upper-bound effective linewidth of 9.1 MHz from the locked laser using a scanning Fabry-Perot interferometer. Our design of a single-mode laser based on a tunable high-Q microresonator can be expanded to quantum-cascade lasers at higher wavelengths and lead to the development of compact, portable, high-performance mid-IR sensors for spectroscopic and sensing applications.

physics.optics↗