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Publications
Yifei Wang; Patrick Landreman; David Schoen; Kye Okabe; Ann Marshall; Umberto Celano; H.-S. Philip Wong; Junghyun Park; Mark L. Brongersma
Electrical tuning of phase-change antennas and metasurfaces Journal Article
In: Nature Nanotechnology, vol. 16, pp. 667–672, 2021.
@article{wang2021electrical,
title = {Electrical tuning of phase-change antennas and metasurfaces},
author = {Yifei Wang and Patrick Landreman and David Schoen and Kye Okabe and Ann Marshall and Umberto Celano and H.-S. Philip Wong and Junghyun Park and Mark L. Brongersma},
doi = {10.1038/s41565-021-00882-8},
year = {2021},
date = {2021-04-19},
journal = {Nature Nanotechnology},
volume = {16},
pages = {667\textendash672},
abstract = {The success of semiconductor electronics is built on the creation of compact, low-power switching elements that offer routing, logic and memory functions. The availability of nanoscale optical switches could have a similarly transformative impact on the development of dynamic and programmable metasurfaces, optical neural networks and quantum information processing. Phase-change materials are uniquely suited to enable their creation as they offer high-speed electrical switching between amorphous and crystalline states with notably different optical properties. Their high refractive index has already been harnessed to fashion them into compact optical antennas. Here, we take the next important step, by showing electrically-switchable phase-change antennas and metasurfaces that offer strong, reversible, non-volatile, multi-phase switching and spectral tuning of light scattering in the visible and near-infrared spectral ranges. Their successful implementation relies on a careful joint thermal and optical optimization of the antenna elements that comprise a silver strip that simultaneously serves as a plasmonic resonator and a miniature heating stage. Our metasurface affords electrical modulation of the reflectance by more than fourfold at 755 nm.},
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pubstate = {published},
tppubtype = {article}
}
The success of semiconductor electronics is built on the creation of compact, low-power switching elements that offer routing, logic and memory functions. The availability of nanoscale optical switches could have a similarly transformative impact on the development of dynamic and programmable metasurfaces, optical neural networks and quantum information processing. Phase-change materials are uniquely suited to enable their creation as they offer high-speed electrical switching between amorphous and crystalline states with notably different optical properties. Their high refractive index has already been harnessed to fashion them into compact optical antennas. Here, we take the next important step, by showing electrically-switchable phase-change antennas and metasurfaces that offer strong, reversible, non-volatile, multi-phase switching and spectral tuning of light scattering in the visible and near-infrared spectral ranges. Their successful implementation relies on a careful joint thermal and optical optimization of the antenna elements that comprise a silver strip that simultaneously serves as a plasmonic resonator and a miniature heating stage. Our metasurface affords electrical modulation of the reflectance by more than fourfold at 755 nm.
Junghyun Park; Soo Jin Kim; Patrick Landreman; Mark L. Brongersma
An Over‐Coupled Phase‐Change Metasurface for Efficient Reflection Phase Modulation Journal Article
In: Advanced Optical Materials, vol. 8, no. 2000745, 2020.
@article{parkover,
title = {An Over‐Coupled Phase‐Change Metasurface for Efficient Reflection Phase Modulation},
author = {Junghyun Park and Soo Jin Kim and Patrick Landreman and Mark L. Brongersma},
doi = {10.1002/adom.202000745},
year = {2020},
date = {2020-08-26},
journal = {Advanced Optical Materials},
volume = {8},
number = {2000745},
abstract = {An over‐coupled, thermally tunable metasurface reflect‐array that employs the phase change material Ge2Sb2Te5 (GST) is presented. The metasurface is constructed from gap plasmon cavities in which GST is incorporated as the active switching medium. Upon annealing at 200 °C for 10 min, the GST layer undergoes a transition from the amorphous state to the crystalline state, and this leads to a unity‐order increase of the refractive index. This is accompanied by a spectral shift of 1.6 µm in the resonance wavelength of the plasmonic cavities, larger than their resonance linewidth of 1.2 µm. It is shown that the low material absorption of the GST layer enables operation of the metasurface in the desirable over‐coupled regime. The numerical analysis indicates that this facilitates large changes in the reflection phase (up to 270°) and amplitude. The work opens the possibility of creating efficient reconfigurable metasurfaces for various applications, including holographic displays and image sensors.},
keywords = {},
pubstate = {published},
tppubtype = {article}
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An over‐coupled, thermally tunable metasurface reflect‐array that employs the phase change material Ge2Sb2Te5 (GST) is presented. The metasurface is constructed from gap plasmon cavities in which GST is incorporated as the active switching medium. Upon annealing at 200 °C for 10 min, the GST layer undergoes a transition from the amorphous state to the crystalline state, and this leads to a unity‐order increase of the refractive index. This is accompanied by a spectral shift of 1.6 µm in the resonance wavelength of the plasmonic cavities, larger than their resonance linewidth of 1.2 µm. It is shown that the low material absorption of the GST layer enables operation of the metasurface in the desirable over‐coupled regime. The numerical analysis indicates that this facilitates large changes in the reflection phase (up to 270°) and amplitude. The work opens the possibility of creating efficient reconfigurable metasurfaces for various applications, including holographic displays and image sensors.
Patrick E. Landreman; Hamidreza Chalabi; Junghyun Park; Mark L. Brongersma
Fabry-Perot description for Mie resonances of rectangular dielectric nanowire optical resonators Journal Article
In: Opt. Express, vol. 24, pp. 29760, 2016.
@article{Landreman:2016,
title = {Fabry-Perot description for Mie resonances of rectangular dielectric nanowire optical resonators},
author = {Patrick E. Landreman and Hamidreza Chalabi and Junghyun Park and Mark L. Brongersma},
doi = {10.1364/OE.24.029760},
year = {2016},
date = {2016-12-26},
journal = {Opt. Express},
volume = {24},
pages = {29760},
abstract = {We show that a dielectric nanowire (NW) with a rectangular cross section can effectively be modeled as a Fabry-Perot cavity formed by truncating a dielectric slab waveguide. By calculating the mode indices of the supported waveguide modes and the reflection phase pickup of the guided waves from the end facets, we can numerically predict the spectral locations of optical, Mie-like resonances for such NWs. This type of analysis must be performed twice in order to account for all resonances of these structures, corresponding to light propagating in the vertical or horizontal directions. The model shows excellent agreement with full-field simulations. We show how the refractive index of both the NW itself and neighboring materials and substrates impact the resonant properties. Our results can aid the development of NW-based optoelectronic devices, for which rectangular cross sections are much simpler to fabricate using top-down fabrication procedures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We show that a dielectric nanowire (NW) with a rectangular cross section can effectively be modeled as a Fabry-Perot cavity formed by truncating a dielectric slab waveguide. By calculating the mode indices of the supported waveguide modes and the reflection phase pickup of the guided waves from the end facets, we can numerically predict the spectral locations of optical, Mie-like resonances for such NWs. This type of analysis must be performed twice in order to account for all resonances of these structures, corresponding to light propagating in the vertical or horizontal directions. The model shows excellent agreement with full-field simulations. We show how the refractive index of both the NW itself and neighboring materials and substrates impact the resonant properties. Our results can aid the development of NW-based optoelectronic devices, for which rectangular cross sections are much simpler to fabricate using top-down fabrication procedures.
Peter Zalden; Michael J. Shu; Frank Chen; Xiaoxi Wu; Yi Zhu; Haidan Wen; Scott Johnston; Zhi-Xun Shen; Patrick Landreman; Mark Brongersma; Scott W. Fong; H.-S. Philip Wong; Meng-Ju Sher; Peter Jost; Matthias Kaes; Martin Salinga; Alexander von Hoegen; Matthias Wuttig; and Aaron M. Lindenberg
Picosecond electric-field-induced threshold switching in phase-change materials Journal Article
In: Phys. Rev. Lett., vol. 117, pp. 067601, 2016.
@article{Zalden:2016,
title = {Picosecond electric-field-induced threshold switching in phase-change materials},
author = {Peter Zalden and Michael J. Shu and Frank Chen and Xiaoxi Wu and Yi Zhu and Haidan Wen and Scott Johnston and Zhi-Xun Shen and Patrick Landreman and Mark Brongersma and Scott W. Fong and H.-S. Philip Wong and Meng-Ju Sher and Peter Jost and Matthias Kaes and Martin Salinga and Alexander von Hoegen and Matthias Wuttig and and Aaron M. Lindenberg},
doi = {10.1103/PhysRevLett.117.067601},
year = {2016},
date = {2016-08-05},
journal = {Phys. Rev. Lett.},
volume = {117},
pages = {067601},
abstract = {Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag4In3Sb67Te26. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales\textemdashfaster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag4In3Sb67Te26. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales—faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.
Patrick Landreman
Stanford University, 2016.
@phdthesis{PatrickLandremanthesis,
title = {Phase change optical antennas: applications of germanium antimony telluride for the dynamic control of light},
author = {Patrick Landreman},
url = {http://purl.stanford.edu/nw312qt8861},
year = {2016},
date = {2016-08-01},
school = {Stanford University},
abstract = {As materials are reduced from bulk quantities to micron or sub-micron dimensions, remarkable changes in the optical properties of these materials appear. Over the past several decades, the physics of these small structures has been studied, leading to a host of novel ways to control light. The devices which achieve this control are referred to as optical antennas, in analogy with their radio-frequency counterparts. In this thesis, we illustrate a model for understanding the optical properties of antennas fabricated out of dielectric materials using conventional semiconductor processing methods, such as etching or lift-off. This model, which operates faster than standard brute-force full-field simulation methods, reveals the existence of two classes of Fabry-Perot type resonances in such structures. Knowledge of these separate modes enables us to manipulate them using the properties of adjacent materials, including the substrate on which the antenna is placed. After developing this theory, the intuition is applied to the design of antennas using so-called phase change chalcogenide materials - that is, the alloys of germanium, antimony, and tellurium. These materials show uniquely large refractive index contrasts in the near- to mid-infrared bands of the electromagnetic spectrum. While previous studies have applied films of these materials near established optical device designs, our project demonstrates the first individual, patterned phase change optical antennas. The antennas perform remarkably well, allowing the post-fabrication tuning of an optical resonance over a free spectral range, from 3.2 to 4.5 um. Finally, from our experience developing these antennas, we propose and fabricate a second generation of phase change optical antennas. The newer design is based on coupled metallic nanorods, and enables independent optimization of the phase change and optical behavior of the antenna device. We show a proof-of-principle experiment in which the resonances of such antennas are also tunable post-fabrication, and we suggest a path towards measurements on individual, electrically-controlled devices.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
As materials are reduced from bulk quantities to micron or sub-micron dimensions, remarkable changes in the optical properties of these materials appear. Over the past several decades, the physics of these small structures has been studied, leading to a host of novel ways to control light. The devices which achieve this control are referred to as optical antennas, in analogy with their radio-frequency counterparts. In this thesis, we illustrate a model for understanding the optical properties of antennas fabricated out of dielectric materials using conventional semiconductor processing methods, such as etching or lift-off. This model, which operates faster than standard brute-force full-field simulation methods, reveals the existence of two classes of Fabry-Perot type resonances in such structures. Knowledge of these separate modes enables us to manipulate them using the properties of adjacent materials, including the substrate on which the antenna is placed. After developing this theory, the intuition is applied to the design of antennas using so-called phase change chalcogenide materials - that is, the alloys of germanium, antimony, and tellurium. These materials show uniquely large refractive index contrasts in the near- to mid-infrared bands of the electromagnetic spectrum. While previous studies have applied films of these materials near established optical device designs, our project demonstrates the first individual, patterned phase change optical antennas. The antennas perform remarkably well, allowing the post-fabrication tuning of an optical resonance over a free spectral range, from 3.2 to 4.5 um. Finally, from our experience developing these antennas, we propose and fabricate a second generation of phase change optical antennas. The newer design is based on coupled metallic nanorods, and enables independent optimization of the phase change and optical behavior of the antenna device. We show a proof-of-principle experiment in which the resonances of such antennas are also tunable post-fabrication, and we suggest a path towards measurements on individual, electrically-controlled devices.
Patrick E Landreman; Mark L Brongersma
Deep-Subwavelength Semiconductor Nanowire Surface Plasmon Polariton Couplers Journal Article
In: Nano letters, vol. 14, no. 2, pp. 429–434, 2014.
@article{landreman2014deepb,
title = {Deep-Subwavelength Semiconductor Nanowire Surface Plasmon Polariton Couplers},
author = { Patrick E Landreman and Mark L Brongersma},
doi = {10.1021/nl402980j},
year = {2014},
date = {2014-01-01},
journal = {Nano letters},
volume = {14},
number = {2},
pages = {429--434},
publisher = {ACS Publications},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
