More Like this

1. General framework for ultrafast nonlinear photonics: unifying single and multi-envelope treatments [Invited]

   https://doi.org/10.1364/OE.513856  

   Phillips, C. R.; Jankowski, M.; Flemens, N.; Fejer, M. M. (January 2024, Optics Express)

   Numerical modeling of ultrashort pulse propagation is important for designing and understanding the underlying dynamical processes in devices that take advantage of highly nonlinear interactions in dispersion-engineered optical waveguides. Once the spectral bandwidth reaches an octave or more, multiple types of nonlinear polarization terms can drive individual optical frequencies. This issue is particularly prominent inχ⁽²⁾devices where all harmonics of the input pulse are generated and there can be extensive spectral overlap between them. Single-envelope approaches to pulse propagation have been developed to address these complexities; this has led to a significant mismatch between the strategies used to analyze moderate-bandwidth devices (usually involving multi-envelope models) and those used to analyze octave-spanning devices (usually involving models with one envelope per waveguide mode). Here we unify the different strategies by developing a common framework, applicable to any optical bandwidth, that allows for a side-by-side comparison between single- and multi-envelope models. We include bothχ⁽²⁾andχ⁽³⁾interactions in these models, with emphasis onχ⁽²⁾interactions. We show a detailed example based on recent supercontinuum generation experiments in a thin-film LiNbO₃on sapphire quasi-phase-matching waveguide. Our simulations of this device show good agreement between single- and multi-envelope models in terms of the frequency comb properties of the electric field, even for multi-octave-spanning spectra. Building on this finding, we explore how the multi-envelope approach can be used to develop reduced models that help build physical insights about new ultrafast photonics devices enabled by modern dispersion-engineered waveguides, and discuss practical considerations for the choice of such models. More broadly, we give guidelines on the pros and cons of the different modeling strategies in the context of device design, numerical efficiency, and accuracy of the simulations. 

   more » « less
2. Towards an engineering framework for ultrafast quantum nonlinear optics

   https://doi.org/10.1117/12.2576098  

   Yanagimoto, Ryotatsu; Ng, Edwin; Onodera, Tatsuhiro; Mabuchi, Hideo (March 2021, Ultrafast Phenomena and Nanophotonics XXV)

   Betz, Markus; Elezzabi, Abdulhakem Y. (Ed.)

   The advent of dispersion-engineered and highly nonlinear nanophotonics is expected to open up an all-optical path towards the strong-interaction regime of quantum optics by combining high transverse field confinement with ultra-short-pulse operation. Obtaining a full understanding of photon dynamics in such broadband devices, however, poses major challenges in the modeling and simulation of multimode non-Gaussian quantum physics, highlighting the need for sophisticated reduced models that facilitate efficient numerical study while providing useful physical insight. In this manuscript, we review our recent efforts in modeling broadband optical systems at varying levels of abstraction and generality, ranging from multimode extensions of quantum input-output theory for sync-pumped oscillators to the development of numerical methods based on a field-theoretic description of nonlinear waveguides. We expect our work not only to guide ongoing theoretical and experimental efforts towards next-generation quantum devices but also to uncover essential physics of broadband quantum photonics. 

   more » « less
3. Ultra-low-power second-order nonlinear optics on a chip

   https://doi.org/10.1038/s41467-022-31134-5  

   McKenna, Timothy P.; Stokowski, Hubert S.; Ansari, Vahid; Mishra, Jatadhari; Jankowski, Marc; Sarabalis, Christopher J.; Herrmann, Jason F.; Langrock, Carsten; Fejer, Martin M.; Safavi-Naeini, Amir H. (December 2022, Nature Communications)

   Abstract Second-order nonlinear optical processes convert light from one wavelength to another and generate quantum entanglement. Creating chip-scale devices to efficiently control these interactions greatly increases the reach of photonics. Existing silicon-based photonic circuits utilize the third-order optical nonlinearity, but an analogous integrated platform for second-order nonlinear optics remains an outstanding challenge. Here we demonstrate efficient frequency doubling and parametric oscillation with a threshold of tens of micro-watts in an integrated thin-film lithium niobate photonic circuit. We achieve degenerate and non-degenerate operation of the parametric oscillator at room temperature and tune its emission over one terahertz by varying the pump frequency by hundreds of megahertz. Finally, we observe cascaded second-order processes that result in parametric oscillation. These resonant second-order nonlinear circuits will form a crucial part of the emerging nonlinear and quantum photonics platforms. 

   more » « less
4. Ultrafast second-order nonlinear photonics—from classical physics to non-Gaussian quantum dynamics: a tutorial

   https://doi.org/10.1364/AOP.495768  

   Jankowski, Marc; Yanagimoto, Ryotatsu; Ng, Edwin; Hamerly, Ryan; McKenna, Timothy P; Mabuchi, Hideo; Fejer, M M (June 2024, Advances in Optics and Photonics)

   Photonic integrated circuits with second-order (χ⁽²⁾) nonlinearities are rapidly scaling to remarkably low powers. At this time, state-of-the-art devices achieve saturated nonlinear interactions with thousands of photons when driven by continuous-wave lasers, and further reductions in these energy requirements enabled by the use of ultrafast pulses may soon push nonlinear optics into the realm of single-photon nonlinearities. This tutorial reviews these recent developments in ultrafast nonlinear photonics, discusses design strategies for realizing few-photon nonlinear interactions, and presents a unified treatment of ultrafast quantum nonlinear optics using a framework that smoothly interpolates from classical behaviors to the few-photon scale. These emerging platforms for quantum optics fundamentally differ from typical realizations in cavity quantum electrodynamics due to the large number of coupled optical modes. Classically, multimode behaviors have been well studied in nonlinear optics, with famous examples including soliton formation and supercontinuum generation. In contrast, multimode quantum systems exhibit a far greater variety of behaviors, and yet closed-form solutions are even sparser than their classical counterparts. In developing a framework for ultrafast quantum optics, we identify what behaviors carry over from classical to quantum devices, what intuition must be abandoned, and what new opportunities exist at the intersection of ultrafast and quantum nonlinear optics. Although this article focuses on establishing connections between the classical and quantum behaviors of devices withχ⁽²⁾nonlinearities, the frameworks developed here are general and are readily extended to the description of dynamical processes based on third-orderχ⁽³⁾nonlinearities. 

   more » « less
5. Modeling method for concentric ring resonators with dispersion engineering

   https://doi.org/10.1364/OE.577296  

   Hasan, Mehedi; Baek, Seungyup; Bernussi, Ayrton; Kim, Sangsik (November 2025, Optics Express)

   We introduce a geometry-guided design method in concentric ring resonators for dispersion engineering. Using eigenmode simulations of a single ring, we construct a two-dimensional round-trip optical path length (OPL) map that systematically identifies phase-matched geometries without exhaustive parameter sweeps. The OPL map finds feasible ring and gap combinations for efficient coupling, also revealing the design limits. With this approach, we design a 50 nm-thick Si₃N₄concentric ring resonator that achieves anomalous dispersion in a weakly-guided mode—a regime that typically exhibits normal dispersion in single-ring configurations. Lugiato–Lefever equation (LLE) simulations confirm that this dispersion-engineered concentric ring can support a bright soliton in a weakly guided mode, overcoming the dispersion limit due to a weak confinement. The proposed modeling method is generalized and readily extendable to a wide range of material platforms and wavelength regimes, providing a powerful tool for diverse integrated nonlinear photonic applications. 

   more » « less