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1. General theory and observation of Cherenkov radiation induced by multimode solitons

   https://doi.org/10.1038/s42005-021-00640-1  

   Eftekhar, M. A. ; Lopez-Aviles, H. ; Wise, F. W. ; Amezcua-Correa, R. ; Christodoulides, D. N. ( December 2021 , Communications Physics)

   Abstract Advancements in computational capabilities along with the possibility of accessing high power levels have stimulated a reconsideration of multimode fibers. Multimode fibers are nowadays intensely pursued in terms of addressing longstanding issues related to information bandwidth and implementing new classes of high-power laser sources. In addition, the multifaceted nature of this platform, arising from the complexity associated with hundreds and thousands of interacting modes, has provided a fertile ground for observing novel physical effects. However, this same complexity has introduced a formidable challenge in understanding these newly emerging physical phenomena. Here, we provide a comprehensive theory capable of explaining the distinct Cherenkov radiation lines produced during multimode soliton fission events taking place in nonlinear multimode optical fibers. Our analysis reveals that this broadband dispersive wave emission is a direct byproduct of the nonlinear merging of the constituent modes comprising the resulting multimode soliton entities, and is possible in both the normal and anomalous dispersive regions. These theoretical predictions are experimentally and numerically corroborated in both parabolic and step-index multimode silica waveguides. Effects arising from different soliton modal compositions can also be accounted for, using this model. At a more fundamental level, our results are expected to further facilitate ourmore »understanding of the underlying physics associated with these complex “many-body” nonlinear processes.« less
2. Nonlinear multimode photonics: nonlinear optics with many degrees of freedom

   https://doi.org/10.1364/OPTICA.461981  

   Wright, Logan G. ; Renninger, William H. ; Christodoulides, Demetri N. ; Wise, Frank W. ( July 2022 , Optica)

   The overall goal of photonics research is to understand and control light in new and richer ways to facilitate new and richer applications. Many major developments to this end have relied on nonlinear optical techniques, such as lasing, mode-locking, and parametric downconversion, to enable applications based on the interactions of coherent light with matter. These processes often involve nonlinear interactions between photonic and material degrees of freedom spanning multiple spatiotemporal scales. While great progress has been made with relatively simple optimizations, such as maximizing single-mode coherence or peak intensity alone, the ultimate achievement of coherent light engineering is complete, multidimensional control of light–light and light–matter interactions through tailored construction of complex optical fields and systems that exploit all of light’s degrees of freedom. This capability is now within sight, due to advances in telecommunications, computing, algorithms, and modeling. Control of highly multimode optical fields and processes also facilitates quantitative and qualitative advances in optical imaging, sensing, communication, and information processing since these applications directly depend on our ability to detect, encode, and manipulate information in as many optical degrees of freedom as possible. Today, these applications are increasingly being enhanced or enabled by both multimode engineering and nonlinearity. Here, wemore »provide a brief overview of multimode nonlinear photonics, focusing primarily on spatiotemporal nonlinear wave propagation and, in particular, on promising future directions and routes to applications. We conclude with an overview of emerging processes and methodologies that will enable complex, coherent nonlinear photonic devices with many degrees of freedom.

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3. Multimode-fiber-based single-shot full-field measurement of optical pulses

   https://doi.org/10.1364/OL.388616  

   Xiong, Wen ; Gertler, Shai ; Yilmaz, Hasan ; Cao, Hui ( April 2020 , Optics Letters)

   Multimode fibers are explored widely for optical communication, spectroscopy, imaging, and sensing applications. Here we demonstrate a single-shot full-field temporal measurement technique based on a multimode fiber. The complex spatiotemporal speckle field is created by a reference pulse propagating through the fiber, and it interferes with a signal pulse. From the time-integrated interference pattern, both the amplitude and the phase of the signal are retrieved. The simplicity and high sensitivity of our scheme illustrate the potential of multimode fibers as versatile and multi-functional sensors.
4. Multimode nonlinear dynamics in spatiotemporal mode-locked anomalous-dispersion lasers

   https://doi.org/10.1364/OL.471457  

   Wu, Yuhang ; Christodoulides, Demetrios N. ; Wise, Frank W. ( August 2022 , Optics Letters)

   Spatiotemporal mode-locking in a laser with anomalous dispersion is investigated. Mode-locked states with varying modal content can be observed, but we find it difficult to observe highly-multimode states. We describe the properties of these mode-locked states and compare them to the results of numerical simulations. Prospects for the generation of highly-multimode states and lasers based on multimode soliton formation are discussed.
5. Overcoming Challenges in Large-Core SI-POF-Based System-Level Modeling and Simulation

   https://doi.org/10.3390/photonics6030088  

   Richards, Dwight ; Lopez, Alicia ; Losada, M. Angeles ; Mena, Pablo V. ; Ghillino, Enrico ; Mateo, Javier ; Antoniades, Neo ; Jiang, Xin ( September 2019 , Photonics)

   The application areas for plastic optical fibers such as in-building or aircraft networks usually have tight power budgets and require multiple passive components. In addition, advanced modulation formats are being considered for transmission over plastic optical fibers (POFs) to increase spectral efficiency. In this scenario, there is a clear need for a flexible and dynamic system-level simulation framework for POFs that includes models of light propagation in POFs and the components that are needed to evaluate the entire system performance. Until recently, commercial simulation software either was designed specifically for single-mode glass fibers or modeled individual guided modes in multimode fibers with considerable detail, which is not adequate for large-core POFs where there are millions of propagation modes, strong mode coupling and high variability. These are some of the many challenges involved in the modeling and simulation of POF-based systems. Here, we describe how we are addressing these challenges with models based on an intensity-vs-angle representation of the multimode signal rather than one that attempts to model all the modes in the fiber. Furthermore, we present model approaches for the individual components that comprise the POF-based system and how the models have been incorporated into system-level simulations, including the commercialmore »software packages SimulinkTM and ModeSYSTM.« less