arXiv subjects

Gustavo S. Wiederhecker

Publications and source records attributed to Gustavo S. Wiederhecker.

At least 19 recordsLinked to original sources

arXiv2026

From order to chaos in a chip-scale Kerr parametric oscillator

Integrated photonics has enabled a wide class of chip-scale light sources and quantum technologies. Within this field, microresonator-based degenerate optical parametric oscillators (DOPOs) have gained prominence. Above a critical power threshold, these systems undergo spontaneous symmetry breaking to settle into one of two stable, π-phase-shifted states -- a mechanism successfully used for quantum random number generation and photonic Ising machines. Here, we show that DOPOs based on the Kerr nonlinearity host a significantly broader range of nonlinear dynamics than previously explored. Using a silicon nitride microring resonator, we experimentally identify Hopf bifurcations that trigger a transition from stationary operation to self-sustained oscillations at MHz frequencies. By adjusting pump detunings and powers, we achieve turnkey control over these oscillatory regimes, navigating the system between stable binary states and periodic limit cycles. Furthermore, we report the experimental observation of period-doubling bifurcations, which numerical simulations reveal as the precursor to a cascading instability culminating in chaos at elevated pump powers. Our results establish a framework for controlling nonlinear instabilities in chip-scale parametric oscillators, with applications in programmable photonic hardware and dynamical optical computing.

physics.optics↗

arXiv2026

Vectorial engineering of second-harmonic generation in silicon-based waveguides integrated with 2D materials

Integrating 2D materials onto on-chip photonic devices holds significant potential for nonlinear frequency conversion across various applications. The lack of inversion symmetry in monolayers of transition metal dichalcogenides (TMDs), e.g., MoS$_2$, is particularly attractive for enabling nonlinear phenomena based on $χ^{(2)}$ in silicon-based photonic devices incorporated with these materials, which has been previously demonstrated. However, reports have largely overlooked the need to consider, in the nonlinear modal interaction, both the tensorial nature of the TMD's second-order susceptibility and the full vectorial nature of the electromagnetic fields. In this work, we investigate second-harmonic generation (SHG) in silicon nitride (SiN) waveguides integrated with a monolayer of MoS$_2$. We experimentally observed an enhancement in SHG in MoS$_2$-loaded waveguides compared to those without the monolayer. Notably, this enhancement occurred even when the dominant electric field component of the pump and/or signal mode was orthogonal to the TMD plane, highlighting co- and cross-polarized SHG interactions. This phenomenon cannot be predicted by the traditionally used scalar models. By taking into account the full vectorial and tensorial natures of the problem, we then designed a waveguide in which a TE pump mode is phase-matched to a TM second-harmonic mode. With a single 110-$μ$m-long MoS$_2$ flake, we experimentally achieved $14\times$ frequency conversion enhancement relative to the non-phase-matched case and $220\times$ enhancement relative to free-space (normal-incidence) excitation. Our work, thus, introduces fundamental guidelines for the design and optimization of nonlinear silicon-photonic devices based on 2D-material hybrid integration. These guidelines are material independent and may lead to significant further conversion efficiency enhancement.

physics.optics↗

arXiv2026

Fourth-harmonic UV light generation in integrated silicon nitride microresonators

Integrated silicon nitride (Si3N4) resonators have emerged as a leading platform for nonlinear photonics, yet generating light at wavelength in the ultraviolet (UV) has remained elusive in single-resonator systems. Here we report the first observation of fourth-harmonic generation reaching the blue and ultraviolet spectral regions in an integrated Si3N4 microring resonator. We systematically investigate the input-power dependence of the wavelength ranges supporting second-, third-, and fourth-harmonic generation, and study the input-power-dependent variation of the circulating fourth-harmonic signal in the UV. These results extend the operational bandwidth of integrated Si3N4 nonlinear photonic platforms to the lower edge of the material transparency window, enabling on-chip UV frequency conversion. Near-ultraviolet generation around 400 nm will enable on-chip excitation of defect-based quantum emitters in hexagonal boron nitride, enhance Raman spectroscopy through increased scattering cross-sections at shorter wavelengths, and support compact fluorescence-based bio-imaging platforms exploiting intrinsic cellular fluorophores.

physics.optics↗

arXiv2026

Hybridized-band parametric oscillations in coupled Kerr microresonators

Coupled resonators form band-like optical states that support rich nonlinearities beyond what is possible in single resonators. In these systems, four-wave mixing mediates interband coupling, displaying multimode dynamics that span both spatial and spectral degrees of freedom. In this study, we propose a framework describing the onset and control of hybridized optical parametric oscillation in three coupled silicon nitride microring resonators. In a symmetric configuration, we observe the emergence of diverse phase-matching pathways defined by the dispersive band structure. We develop an analytical model that captures the parametric gain of these interband processes and derive closed-form expressions for the dominant gain maxima; the analytical framework itself readily extends to more complex coupled networks. We further report an asymmetric design that co-engineers mode overlap and dispersion to operate on a compact 7-GHz spacing, free from mode competition. Our findings establish design principles for engineering nonlinear dynamics in coupled-resonator platforms, with implications for coherent photonic computing and quantum information processing.

physics.optics↗

arXiv2026

Color symmetry breaking in a nonlinear optical microcavity

Spontaneous symmetry breaking leads to diverse phenomena across the natural sciences, from the Higgs mechanism in particle physics to superconductors and collective animal behavior. In photonic systems, the symmetry of light states can be broken when two optical fields interact through the Kerr nonlinearity, as shown in early demonstrations with counterpropagating and cross-polarized modes. Here, we report the first observation of color symmetry breaking in an integrated silicon nitride microring, where spontaneous power imbalance arises between optical mode at different wavelengths, mediated by the Kerr effect. The threshold power for this effect is as low as 19 mW. By examining the system's homogeneous states, we further demonstrate a Kerr-based nonlinear activation-function generator that produces sigmoid-, quadratic-, and leaky-ReLU-like responses. These findings reveal previously unexplored nonlinear dynamics in dual-pumped Kerr resonators and establish new pathways towards compact, all-optical neuromorphic circuits.

physics.optics↗

arXiv2025

Mapping Nonlinear Mode Interactions in Coupled Kerr Resonators

We present a method for resolving spatial mode overlaps in coupled microresonators based on Kerr and thermal cross-phase modulation. Through a pump-probe setup, we measure experimental overlap in a three-ring resonator with good agreement with analytical theory. Our technique can be generalized for describing nonlinear interactions in more complex multi- and coupled-mode systems.

physics.optics↗

arXiv2025

Cross-Polarized Stimulated Brillouin Scattering in Lithium Niobate Waveguides

We report on the experimental demonstration of cross-polarization backward stimulated Brillouin scattering (BSBS) in lithium niobate on insulator (LNOI) waveguides. Performing polarization-sensitive pump and probe measurements, we captured both intra- and intermodal scattering between counterpropagating fundamental optical modes. Remarkably, cross-polarization scattering achieved SBS gains that exceeded $G_{B}=$80m$^{-1}$W$^{-1}$. This substantial gain not only broadens the utility of polarization in SBS but also paves the way for high-performance devices, including ultranarrowband lasers, robust broadband nonreciprocal devices, RF filters, and microwave-to-optical converters.

physics.optics↗

arXiv2024

Optomechanical microgear cavity

We introduce a novel optomechanical microgear cavity for both optical and mechanical isotropic materials, featuring a single etch configuration. The design leverages a conjunction of phononic and photonic crystal-like structures to achieve remarkable confinement of both optical and mechanical fields. The microgear cavity we designed in amorphous silicon nitride exhibits a mechanical resonance at 4.8 GHz, and whispering gallery modes in the near-infrared, with scattering-limited quality factors above the reported material limit of up $10^7$. Notably, the optomechanical photoelastic overlap contribution reaches 75% of the ideal configuration seen in a floating ring structure.

physics.optics↗

arXiv2024

Tunable Degenerate Optical Parametric Oscillation with Coupled Microresonators

Microresonator-based degenerate optical parametric oscillation (DOPO) has recently been explored as a compelling platform for all-optical computing and quantum information applications, such as truly random number generation and the production of squeezed states of light. Emerging research has highlighted the potential of coupled microresonators, or photonic molecules, as a novel avenue for spectral engineering, unlocking an extra degree of freedom for the optimization of four-wave mixing interactions. Here, we demonstrate DOPO within the coupled modes of a silicon nitride triple-state photonic molecule. Our design introduces a distinctive mechanism for spectral engineering, using microheaters to individually tune the resonance spectral positions, thus enabling dynamic local dispersion control within the coupled modes. We successfully generate a DOPO signal with active efficiency control and explore the optical mode spacing in the tens of gigahertz range to use native phase-locked optical pumps driven by a radio-frequency source.

physics.optics↗

arXiv2023

Dissipative Optomechanics in High-Frequency Nanomechanical Resonators

The coherent transduction of information between microwave and optical domains is a fundamental building block for future quantum networks. A promising way to bridge these widely different frequencies is using high-frequency nanomechanical resonators interacting with low-loss optical modes. State-of-the-art optomechanical devices rely on purely dispersive interactions that are enhanced by a large photon population in the cavity. Additionally, one could use dissipative optomechanics, where photons can be scattered directly from a waveguide into a resonator hence increasing the degree of control of the acousto-optic interplay. Hitherto, such dissipative optomechanical interaction was only demonstrated at low mechanical frequencies, precluding prominent applications such as the quantum state transfer between photonic and phononic domains. Here, we show the first dissipative optomechanical system operating in the sideband-resolved regime, where the mechanical frequency is larger than the optical linewidth. Exploring this unprecedented regime, we demonstrate the impact of dissipative optomechanical coupling in reshaping both mechanical and optical spectra. Our figures represent a two-order-of-magnitude leap in the mechanical frequency and a tenfold increase in the dissipative optomechanical coupling rate compared to previous works. Further advances could enable the individual addressing of mechanical modes and help mitigate optical nonlinearities and absorption in optomechanical devices.

physics.optics↗

arXiv2023

Synchronization of silicon thermal-free-carrier oscillators

Recent exploration of collective phenomena in oscillator arrays has highlighted its potential for accessing a range of physical phenomena, from fundamental quantum many-body dynamics to the solution of practical optimization problems using photonic Ising machines. Spontaneous oscillations often arise in these oscillator arrays as an imbalance between gain and loss. Due to coupling between array individuals, the spontaneous oscillation is constrained and lead to interesting collective behavior, such as synchronized oscillations in optomechanical oscillator arrays, ferromagnetic-like coupling in delay-coupled optical parametric oscillators and binary phase states in coupled laser arrays. A key aspect of arrays is not only the coupling between its individuals but also their compliance towards neighbor stimuli. One self-sustaining photonic oscillator that can be readily implemented in a scalable foundry-based technology is based on the interaction of free-carriers, temperature and optical field of a resonant silicon photonic microcavity. Here we demonstrate that these silicon thermal-free-carrier oscillators are extremely compliant to external excitation and can be synchronized up to their 16$^\text{th}$ harmonic using a weak seed. Exploring this unprecedented compliance to external stimuli, we also demonstrate robust synchronization between two thermal free carrier oscillators.

physics.optics↗

arXiv2023

Stimulated Brillouin scattering by surface acoustic waves in lithium niobate waveguides

We numerically demonstrate that Lithium Niobate on Insulator (LNOI) waveguides may support confined short-wavelength surface acoustic waves that interact strongly with optical fields through backward stimulated Brillouin scattering in both $Z$ and $X$-cut orientation. We conduct fully anisotropic simulations that consider not only moving boundary and photoelastic forces, but also roto-optic forces for the Brillouin interaction. Our results indicate that photoelasticity dominates the Brillouin gain and can reach as high as $G_{B}/Q_{m}$ = 0.43 W$^{-1}$m$^{-1}$ in standard ridge waveguides

physics.optics↗

arXiv2022

Third-harmonic generation in silica wedge resonators

Whispering-gallery-mode microcavities are known to have high optical quality factor, making them suitable for nonlinear optical interactions. Here, third-harmonic generation is observed using a relatively small radius wedge silicon oxide optical microcavity. The small radii wedge microdisks can be dispersion-tailored to obtain either normal or anomalous group velocity dispersion. In our case, we operate in the normal dispersion regime preventing frequency comb generation by suppressing infrared cascading four-wave mixing. This allows for a clean third harmonic generation at phase-matched visible optical modes. Tunability of the third-harmonic emission is obtained due to a combination of the thermo-optical and Kerr effects. An additional thermal control of the phase matching condition allows for optimizing third-harmonic generation, and agreement between this process and couple-mode theory is demonstrated.

physics.optics↗

arXiv2022

Silicon anisotropy in a bi-dimensional optomechanical cavity

In this work, we study the effects of mechanical anisotropy in a 2D optomechanical crystal geometry. We fabricate and measure devices with different orientations, showing the dependence of the mechanical spectrum and the optomechanical coupling with the relative angle of the device to the crystallography directions of silicon. Our results show that the device orientation strongly affects its mechanical band structure, which makes the devices more susceptible to fabrication imperfections. Finally, we show that our device is compatible with cryogenic measurements reaching ground state occupancy of 0.2 phonons at mK temperature.

quant-ph↗

arXiv2022

Optimization of diamond optomechanical crystal cavities

Due to recent development of growing and processing techniques for high-quality single crystal diamond, the large scale production of diamond optomechanical crystal cavities becomes feasible, enabling optomechanical devices that can operate in higher mechanical frequencies and be coupled to two-level systems based on diamond color centers. In this paper we describe a design optimization method to produce diamond optomechanical crystal (OMC) cavities operating at the high-cooperativity regime (close to unity) at room temperature.

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

Accurate modeling and characterization of photothermal forces in optomechanics

Photothermal effects have been pointed out as prominent sources of forces in optomechanical systems, competing with the standard radiation pressure interactions. In this Article, we derive a novel and accurate model for the prediction of photothermal forces and establish how some previous proposals can be complemented to yield precise results. As a proof-of-concept, we perform numerical and experimental tests on GaAs microdisks cavities and obtain striking agreement with our framework, revealing the importance of considering surface photothermal forces and the effects of multiple thermal modes in microphotonic devices.

physics.optics↗

arXiv2020

Intermodal Brillouin scattering in solid-core photonic crystal fibers

We investigate intermodal forward Brillouin scattering in a solid-core PCF, demonstrating efficient power conversion between the HE11 and HE21 modes, with a maximum gain coefficient of 21.4/W/km. By exploring mechanical modes of different symmetries, we observe both polarization-dependent and polarization-independent intermodal Brillouin interaction. Finally, we discuss the role of squeeze film air damping and leakage mechanisms, ultimately critical to the engineering of PCF structures with enhanced interaction between high order optical modes through flexural mechanical modes.

physics.optics↗