Gate Tunable Coupling of Epsilon‐Near‐Zero and Plasmonic Modes

Ghindani, Dipa; Rashed, Alireza R.; Habib, Mohsin; Çağlayan, Hümeyra

doi:10.1002/adom.202100800

Cited by 9 publications

(2 citation statements)

References 28 publications

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“…A propagation length of several microns implies an interaction length of several wavelengths at these NIR frequencies. This large interaction length along with the tight mode confinement and the large sub-picosecond nonlinear response of ITO in its ENZ region make our device an ideal platform for electro-optical control of strong coupling, ultrafast switching, and studying giant ultrafast nonlinearities that do not rely on lossy optical resonances or require sophisticated fabrication techniques. The use of a prism for coupling to the polaritons can also be done away with through the use of appropriate grating couplers .…”

Section: Discussionmentioning

confidence: 99%

Strongly Coupled Plasmon Polaritons in Gold and Epsilon-Near-Zero Bifilms

et al. 2023

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Epsilon-near-zero (ENZ) polaritons in a thin transparent conducting-oxide film exhibit a significant electric field enhancement and localization within the film at frequencies close to their plasma frequency, but do not propagate. Meanwhile, plasmon polariton modes in thin metallic films can propagate for several microns, but are more loosely confined in the metal. Here, we propose a strongly coupled bilayered structure of a thin gold film on a thin indium tin oxide (ITO) film that supports hybrid polariton modes. We experimentally characterize the dispersion of these modes and show that they have propagation lengths of 4−8 μm while retaining mode confinement greater than that of the polariton in gold films by nearly an order of magnitude. We study the tunability of this coupling strength by varying the thickness of the ITO film and show that ultrastrong coupling is possible at certain thicknesses. The unusual linear and nonlinear optical properties of ITO at ENZ frequencies make these bifilms useful for the active tuning of strong coupling, ultrafast switching, and enhanced nonlinear interactions at near-infrared frequencies.

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Section: Discussionmentioning

confidence: 99%

Strongly Coupled Plasmon Polaritons in Gold and Epsilon-Near-Zero Bifilms

et al. 2023

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“…Among the several reports concerning the tuning of the dielectric properties of TCOs and their applications ,,− the vast majority have focused on ITO-based systems, ,,,,− ,,− while little can be found in the literature concerning the active exploitation of TCO materials based on Earth-abundant elements, like AZO. ,− Despite showing the same functionalities, ITO and AZO are technically different. ITO has achieved the lowest resistivity on commercial scale (10 –4 ohm·cm) and is more easily realized in lithographically patterned form .…”

Section: Introductionmentioning

confidence: 99%

In-Operando Optical Spectroscopy of Field-Effect-Gated Al-Doped ZnO

Sygletou

Benedetti

Bona

et al. 2023

ACS Appl. Mater. Interfaces

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Transparent conductive oxides (TCO) have the unique characteristics of combining optical transparency with high electrical conductivity; such a property makes them uniquely alluring for applications in visible and infrared photonics. One of their most interesting features is the large sensitivity of their optical response to the doping level. We performed the active electrical manipulation of the dielectric properties of aluminum-doped ZnO (AZO), a TCO-based on Earth-abundant elements. We actively tuned the optical and electric performances of AZO films by means of an applied voltage in a parallel-plate capacitor configuration, with SrTiO 3 as the dielectric, and monitored the effect of charge injection/depletion by means of inoperando spectroscopic ellipsometry. Calculations of the optical response of the gated system allowed us to extract the spatially resolved variations in the dielectric function of the TCO and infer the injected/depleted charge profile at the interface.

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Graphene Oxides as Epsilon‐Near‐Zero Platforms Operating in Terahertz Frequency Range

Jun,

Yim,

Park

et al. 2023

Laser & Photonics Reviews

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Epsilon‐near‐zero (ENZ) materials, with their unique light manipulation capabilities, have fascinating applications such as cloaking, super‐resolution imaging, energy harvesting, and sensing. Herein, free‐standing graphene oxide films are fabricated whose dielectric constant can be engineered by thermal reduction, resulting in ENZ characteristics at the transition between insulating and metallic phases. The ENZ frequency is found to be 0.4–0.5 THz under an annealing temperature of 200 °C, whereas another ENZ phase appeared at 360 °C. ENZ film can be transferred to curved metal surfaces, serving as superabsorbers that suppress wave reflection from underneath metal surfaces. Hyper‐resolution in nondestructive THz imaging is also possible, owing to superior beaming. Spatial resolution is improved two‐fold by adding the ENZ film, even when the metal pattern is enclosed by a paint layer. Lastly, hybrid sensors are developed by incorporating the meta‐pattern on the free‐standing ENZ substrate. The energy splitting of metamaterial resonance originating from the coupling with ENZ mode is observed. Hybridized devices have proven effective in detecting microorganisms with a low refractive index, owing to the unique dielectric configuration offered by ENZ material. Using the novel ENZ platform, a 15‐fold improvement in microbial sensitivity is achieved compared with the conventional sensors.

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Gate Tunable Coupling of Epsilon‐Near‐Zero and Plasmonic Modes

Cited by 9 publications

References 28 publications

Strongly Coupled Plasmon Polaritons in Gold and Epsilon-Near-Zero Bifilms

Strongly Coupled Plasmon Polaritons in Gold and Epsilon-Near-Zero Bifilms

In-Operando Optical Spectroscopy of Field-Effect-Gated Al-Doped ZnO

Graphene Oxides as Epsilon‐Near‐Zero Platforms Operating in Terahertz Frequency Range

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