133 132 Principal Scientist Profiles Sina Saravi Sina Saravi Principal Scientist Profiles JUNIOR RESEARCH GROUP LEADER FOR NONLINEAR NEUROMORPHIC & QUANTUM PHOTONICS Dr. Saravi leads a junior research group at the Institute of Applied Physics of the Friedrich Schiller University Jena. His research activities focus on utilizing linear and nonlinear nanophotonic systems for realization of diffractive optical neural networks for image recognition/inference applications and sources of quantum light for application in optical quantum technologies. SINA SARAVI RESEARCH AREAS Dr. Saravi’s research focus on the development of all-optical diffractive neural networks, designed by machine-learning algorithms, and utilizing the unique capabilities of nanostructured metasurfaces as the implementation platform. Furthermore, he investigates novel sources of quantum light (e.g. entangled photon pairs) in nonlinear nanophotonic systems, especially ones that are hybridized with atomic/atom-like systems. In summary, his research focuses on: • Diffractive optical neural networks and machine learning • Nonlinear metasurfaces • Hybrid nonlinear quantum optical systems TEACHING FIELDS Dr. Saravi has taught master-level courses on: • Quantum Optics • Advanced Quantum Optics RESEARCH METHODS Dr. Saravi uses the following theoretical and experimental methods in his research: • Classical and quantum nonlinear parametric interactions are formulated using Green-function methods, quasinormal-mode expansions, and Lindblad master equation. • FDTD and FEM methods are used for rigorous simulation of the linear and nonlinear optical properties of nanophotonic systems. • Customized microscopy setups are used for characterizing the properties of light generation and scattering in nanophotonic systems. RECENT RESEARCH RESULTS Previous works of Dr. Saravi and coworkers have experimentally demonstrated that nonlinear metasurfaces are ideal platforms to both enhance the efficiency [1] and control the emission properties [2] of the secondharmonic-generation process. More recently, they pushed these results into the quantum regime [3], showing that nonlinear nanoresonators (the constituting elements of a nonlinear metasurface) have unique properties for generation of entangled photon-pair states, where both the directionality and polarization state of the biphoton state can be controlled by simple tuning of the system parameters. These results motivate the utilization of metasurfaces for realizing engineered scattering responses and efficient nonlinear activation elements in our development of all-optical diffractive neural networks. Furthermore, Dr. Saravi and his team pursue the design of novel sources of quantum light, where nonlinear sources of photon pairs/squeezed light are hybridized with atomic/ atom-like systems, where they have already shown that the presence of the atom-like system fundamentally modifies the dynamics of quantum light generation in such systems [4]. Moreover, they also developed theoretical formulations, based on the Green-function method, to study the dynamics of high-gain parametric down-conversion processes, which is capable of treating nanostructured systems with inherently complex dispersive and lossy properties [5]. NONLINEAR QUANTUM IMAGING UTILIZING NEAR-FIELD INTERACTIONS The optimal realization of diffractive optical neural networks requires a deep understanding of nonlinear imaging. Dr. Saravi’s team have investigated such physics in the context of quantum imaging, where quantum light is generated in a sub-wavelength-thin nonlinear slab, which interacts with a near-field absorptive nanoparticle [6]. The focus of this investigation was to predict the image of the object, specially to find the limit of spatial resolution achievable in such quantum imaging systems that involve light beams of two different wavelengths: one photon is interacting with the object, and the other photon in the pair, with a different wavelength, is imaged onto a camera. In this case, it was found that the resolution of imaging is only limited by the diffraction limit of the shorter-wavelength photon in the pair. To treat this problem, special attention was given to near-field and non-paraxial formulation of light generation and propagation. [1] Liu et al., Nano Letters 16, 5426 (2016). [2] Lochner et al., ACS Photonics 5, 1786 (2018). [3] Weissflog et al., arXiv:2305.19362 (2023). [4] Saravi et al., Optics Letters 42, 4724 (2017). [5] Krstic et al., Physical Review Research 5, 043228 (2023). [6] Santos et al., Physical Review Letters 128, 173601 (2022). Contact: Phone: + 49 3641 9-47595 Email: sina.saravi@uni-jena.de ´
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