Exploiting degrees of freedom in active nanophotonic devices
<p>The field of nanophotonics has witnessed remarkable progress, driven by the pressing need to expand device functionalities across multiple photonic degrees-of-freedom. Active nanophotonic devices further offer reconfigurable photonic capabilities across temporal scales, but the challenge of...
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| Format: | Thesis |
| Language: | English |
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2023
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| _version_ | 1826314436208492544 |
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| author | Lee, JS |
| author2 | Bhaskaran, H |
| author_facet | Bhaskaran, H Lee, JS |
| author_sort | Lee, JS |
| collection | OXFORD |
| description | <p>The field of nanophotonics has witnessed remarkable progress, driven by the pressing need to expand device functionalities across multiple photonic degrees-of-freedom. Active nanophotonic devices further offer reconfigurable photonic capabilities across temporal scales, but the challenge of seamlessly bridging these dimensions to achieve multifaceted functionalities persists. This thesis tackles this challenge by leveraging multiple photonic bandwidths in compact active nanophotonic devices, thereby maximizing the device functionalities in photonic domains, spatial configurations, and temporal dynamics. To accomplish this, three distinct approaches are experimentally investigated, each harnessing a different property of light — such as polarization, phase and wavelength —across a range of platforms, such as electro-optic nanowires, metasurfaces, and integrated photonic circuits.</p>
<p>First, the thesis introduces the implementation of a polarization-sensitive electro-optic cell using hybridized-active-dielectric nanowires. By utilizing the Ge2Sb2Te5 phase-change alloy as the active material, this cell exhibits a polarization-dependent electrical readout, demonstrating nonlinear switching behavior of a hybrid nanowire. Expanding on this concept, a multi-nanowire configuration harnesses polarization as a tunable vector, enabling polarization-selective (de)multiplexing and computing operations at an extremely compact scale of ≪5 µm. As a result, this breakthrough significantly enhances computing density by several orders of magnitude compared to its electronic counterparts. These findings unlock new possibilities for realizing device reconfigurabilities in polarization-space and portend a new paradigm for a wide range of tunable nanophotonic devices.</p>
<p>The concept of active nanoresonators is further extended by assembling them in a periodic array and implementing an active metasurface. Low-loss, optically-sensitive materials, such as Sb2Se3, are employed to selectively tune optical phase delays based on the geometry and material states of the nanoresonators. This phase-gradient metasurface acts as flat optics, manipulating the emerging wavefront to achieve lensing, steering, or holographic imaging of the optical beam. The active tunability of the material adds extra functionalities, enabling the realization of varifocal zoom lenses in the telecommunication range using a flat metasurface of Sb2Se3 nanopillars. The dynamic reversible switching of such low-loss active material is then investigated using optical or electrically-programmed thermal pulses, leveraging the capabilities of low-loss meta-optics.</p>
<p>In the final chapters of this thesis, the active nanophotonic functionalities are interfaced with integrated photonic circuits. Such a system features the first prototype of photonic spatio-spectral reconfiguration capable of wavelength-selectively addressing the optical states of a single photonic waveguide. By combining the concept of standing-waves in a microring resonator with active Ge2Sb2Te5 nanoantennas, the spatial degrees-of-freedom of guided modes in waveguides are harnessed with active material reconfigurability. Multiple nanoantennas arranged at a compact spacing (~460 nm) realize a multi-spectral modulator, enabling parallel communication of wavelengths and independent modulation of individual nanoantennas at respective channels. Consequently, the optical storage density is observed to exponentially increase as the system gets cascaded, while holding potential for integration with additional electro-optical controllability. These findings present an alternative pathway for maximizing device functionalities along the wavelength dimension in integrated photonic circuits, enabling applications such as high-bandwidth communication and computing.</p> |
| first_indexed | 2024-09-25T04:32:29Z |
| format | Thesis |
| id | oxford-uuid:c779a308-fcec-40ef-ad3d-c14713224dbb |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:32:29Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:c779a308-fcec-40ef-ad3d-c14713224dbb2024-08-30T09:02:14ZExploiting degrees of freedom in active nanophotonic devices Thesishttp://purl.org/coar/resource_type/c_db06uuid:c779a308-fcec-40ef-ad3d-c14713224dbbPhase-change materialsNanophotonicsEnglishHyrax Deposit2023Lee, JSBhaskaran, H<p>The field of nanophotonics has witnessed remarkable progress, driven by the pressing need to expand device functionalities across multiple photonic degrees-of-freedom. Active nanophotonic devices further offer reconfigurable photonic capabilities across temporal scales, but the challenge of seamlessly bridging these dimensions to achieve multifaceted functionalities persists. This thesis tackles this challenge by leveraging multiple photonic bandwidths in compact active nanophotonic devices, thereby maximizing the device functionalities in photonic domains, spatial configurations, and temporal dynamics. To accomplish this, three distinct approaches are experimentally investigated, each harnessing a different property of light — such as polarization, phase and wavelength —across a range of platforms, such as electro-optic nanowires, metasurfaces, and integrated photonic circuits.</p> <p>First, the thesis introduces the implementation of a polarization-sensitive electro-optic cell using hybridized-active-dielectric nanowires. By utilizing the Ge2Sb2Te5 phase-change alloy as the active material, this cell exhibits a polarization-dependent electrical readout, demonstrating nonlinear switching behavior of a hybrid nanowire. Expanding on this concept, a multi-nanowire configuration harnesses polarization as a tunable vector, enabling polarization-selective (de)multiplexing and computing operations at an extremely compact scale of ≪5 µm. As a result, this breakthrough significantly enhances computing density by several orders of magnitude compared to its electronic counterparts. These findings unlock new possibilities for realizing device reconfigurabilities in polarization-space and portend a new paradigm for a wide range of tunable nanophotonic devices.</p> <p>The concept of active nanoresonators is further extended by assembling them in a periodic array and implementing an active metasurface. Low-loss, optically-sensitive materials, such as Sb2Se3, are employed to selectively tune optical phase delays based on the geometry and material states of the nanoresonators. This phase-gradient metasurface acts as flat optics, manipulating the emerging wavefront to achieve lensing, steering, or holographic imaging of the optical beam. The active tunability of the material adds extra functionalities, enabling the realization of varifocal zoom lenses in the telecommunication range using a flat metasurface of Sb2Se3 nanopillars. The dynamic reversible switching of such low-loss active material is then investigated using optical or electrically-programmed thermal pulses, leveraging the capabilities of low-loss meta-optics.</p> <p>In the final chapters of this thesis, the active nanophotonic functionalities are interfaced with integrated photonic circuits. Such a system features the first prototype of photonic spatio-spectral reconfiguration capable of wavelength-selectively addressing the optical states of a single photonic waveguide. By combining the concept of standing-waves in a microring resonator with active Ge2Sb2Te5 nanoantennas, the spatial degrees-of-freedom of guided modes in waveguides are harnessed with active material reconfigurability. Multiple nanoantennas arranged at a compact spacing (~460 nm) realize a multi-spectral modulator, enabling parallel communication of wavelengths and independent modulation of individual nanoantennas at respective channels. Consequently, the optical storage density is observed to exponentially increase as the system gets cascaded, while holding potential for integration with additional electro-optical controllability. These findings present an alternative pathway for maximizing device functionalities along the wavelength dimension in integrated photonic circuits, enabling applications such as high-bandwidth communication and computing.</p> |
| spellingShingle | Phase-change materials Nanophotonics Lee, JS Exploiting degrees of freedom in active nanophotonic devices |
| title | Exploiting degrees of freedom in active nanophotonic devices
|
| title_full | Exploiting degrees of freedom in active nanophotonic devices
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| title_fullStr | Exploiting degrees of freedom in active nanophotonic devices
|
| title_full_unstemmed | Exploiting degrees of freedom in active nanophotonic devices
|
| title_short | Exploiting degrees of freedom in active nanophotonic devices
|
| title_sort | exploiting degrees of freedom in active nanophotonic devices |
| topic | Phase-change materials Nanophotonics |
| work_keys_str_mv | AT leejs exploitingdegreesoffreedominactivenanophotonicdevices |