סמינר: Electro-Optics and Microelectronics Seminar
Dynamic Control and Manipulation of Near-fields Using Direct Feedback
Date:
October,28,2024
Start Time:
14:30 - 15:30
Location:
1061, Meyer Building
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Lecturer:
Jacob Kher-Aldeen
Research Areas:
| In the rapidly advancing field of nanophotonics, the ability to manipulate light at sub-diffraction scales holds paramount importance, with vast implications across many scientific and technological domains, including integrated photonics, plasmonics, optical communications, sensing, and quantum information processing. My research focuses on controlling such fields and its subsequent implications, such as dynamic nanoscale optical trapping. A major challenge in this field is the lack of real-time feedback for shaping of sub-wavelength fields. Current Mapping methods, such as near-field imaging techniques (e.g. NSOM), require scanning, post-processing and long integration times. Consequently, near-field shaping was only obtained by designing coupling grating geometries and controlling the incident field polarization – an approach that is limited in its dynamic application, as any field modification require a complete redesign and fabrication of the coupling structure. A novel approach developed in our lab, known as NNOM, brought the opportunity for simultaneous shaping and mapping of nanophotonic fields in real-time, which is essential for implementing wavefront shaping algorithms with direct feedback, facilitating the creation of complex wave patterns and the correction of degraded nanophotonic structures. Using a spatial light modulator (SLM) for wavefront shaping of incident light beam coupled to a nanophotonic platform, I achieved the maximal available control over surface-wave nanophotonic patterns. Ultimately, the simultaneous shaping and mapping capabilities have enabled us to employ wavefront shaping algorithms with direct and accurate feedback. I demonstrated several applications emanating from this new ability: • Precise control of a nanophotonic focal spot over several squared microns area, with positioning resolution of 30 nm. • Dynamic control over a pair of focal spots. • Smooth switching among different angular momenta using the same coupling platform while preserving their symmetry. • Correction of distorted nanophotonic fields caused by fabrication flaws and system misalignments. This shaping ability facilitates the implementation of numerous applications, including spin-selective excitation of integrated emitters, real-time near-field adaptive optics, and specifically, holographic near-field tweezers. As part of my research, I initiated the development of plasmonic tweezers, focusing on solving an inherent challenge of such tweezers: the strong heat gradients that practically inhibits the trapping beyond a few seconds. By utilizing a pulsed laser beam, we significantly decreased thermal dissipation, allowing us to observe trapping based on localized surface plasmon fields. Achieving dynamic nanoscale trapping can become viable through our ability to perform far-field shaping of plasmonic patterns. Moreover, this approach minimizes heat dissipation by selectively illuminating the coupling grating, paving the way for a stable plasmonic trapping process with free manipulation capabilities across several microns. Ph.D. Under the supervision of Prof. Guy Bartal.
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