Gigahertz speed operation of epsilon-near-zero silicon photonic modulators

Wood, Michael G.; Campione, Salvatore; Parameswaran, S.; Luk, Ting S.; Wendt, Joel R.; Serkland, Darwin K.; Keeler, Gordon Arthur

doi:10.1364/optica.5.000233

Cited by 101 publications

(55 citation statements)

References 22 publications

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“…The electro-optical materials such as graphene and ITO offer the opportunity to implement time-modulated metasurfaces by changing the external bias in time. Due to the quick response of these materials, they allow for modulation speeds up to several gigahertz [29][30][31]. As such, they can be biased using radio-frequency (RF) circuits to realize time-modulated metasurfaces in IR and THz frequencies.…”

Section: Introductionmentioning

confidence: 99%

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a timemodulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulationinduced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.

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Section: Introductionmentioning

confidence: 99%

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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“…The ENZ frequency of CdO is tunable by adjusting its doping level either chemically or through electrostatic gating. Finally, conductive metal oxides including CdO with ENZ responses have found their ways to be integrated with silicon photonics technology 28 , outscoring the possibility of compact, on-chip sources for EUV and attosecond pulses.…”

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confidence: 99%

High-harmonic generation from an epsilon-near-zero material

et al. 2019

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High-harmonic generation (HHG) from a compact, solid-state medium is highly desirable for applications such as coherent attosecond pulse generation and extreme ultra-violet (EUV) spectroscopy 1 , yet the typically weak conversion of pump light to HHG can largely hinder its applications. Here, we use a material operating in its epsilon-near-zero (ENZ) region 2-11 , where the real part of its permittivity vanishes, to greatly boost the efficiency of the HHG process at the microscopic level. In experiments, we report high-harmonic emission up to the 9 th order directly from a low-loss, solid-state ENZ medium: indium-doped cadmium

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“…In epitaxial CdO grown on sapphire, the effect is prominent up to carrier densities of 3.3 × 10 20 cm −3 , as shown in previous studies . We deposited our CdO films on fused silica substrates keeping in mind practical device‐applications where the films are usually deposited on an oxide (SiO 2 , Al 2 O 3 , or HfO 2 ) or on silicon . This led to the growth of polycrystalline CdO films (Figure S1.2, Supporting Information), which increased the Drude‐damping caused by scattering across grain boundaries, compared to epitaxial layers grown on sapphire or magnesium oxide .…”

Section: Resultsmentioning

confidence: 69%

“…The exploration of alternative nanophotonic and plasmonic materials in the last decade has led to the demonstration of practical, low‐loss, and high‐speed optical devices. These emerging materials have been utilized in high‐speed, on‐chip electroabsorption modulators, ultrafast all‐optical switches, high‐temperature broadband absorbers, plasmon‐enhanced optical sensors, low‐loss hybrid photonic‐plasmonic waveguides, and tunable metasurfaces . In particular, transparent conducting oxides (TCOs) have received considerable attention in nanophotonics and plasmonics due to their low optical losses .…”

Section: Introductionmentioning

confidence: 99%

“…Many TCOs are CMOS‐compatible and can be mass‐produced with standard fabrication methods such as sputtering, atomic layer deposition, and pulsed laser deposition . Their carrier concentrations and plasma frequencies can easily be tailored during fabrication by changing the doping‐levels, oxygen concentration, and growth temperatures . More importantly, TCO optical properties can be dynamically tuned post‐fabrication through thermal effects, electrical biasing or optical pumping, an essential property for ultrafast switches.…”

Section: Introductionmentioning

confidence: 99%

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Broadband, High‐Speed, and Large‐Amplitude Dynamic Optical Switching with Yttrium‐Doped Cadmium Oxide

Saha

Diroll

Shank

et al. 2019

Adv Funct Materials

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Transparent conducting oxides, such as doped indium oxide, zinc oxide, and cadmium oxide (CdO), have recently attracted attention as tailorable materials for applications in nanophotonic and plasmonic devices such as low‐loss modulators and all‐optical switches due to their tunable optical properties, fast optical response, and low losses. In this work, optically induced extraordinarily large reflection changes (up to 135%) are demonstrated in bulk CdO films in the mid‐infrared wavelength range close to the epsilon near zero (ENZ) point. To develop a better understanding of how doping level affects the static and dynamic optical properties of CdO, the evolution of the optical properties with yttrium (Y) doping is investigated. An increase in the metallicity and a blueshift of the ENZ point with increasing Y‐concentrations is observed. Broadband all‐optical switching from near‐infrared to mid‐infrared wavelengths is demonstrated. The major photoexcited carrier relaxation mechanisms in CdO are identified and it is shown that the relaxation times can be significantly reduced by increasing the dopant concentration in the film. This work could pave the way to practical dynamic and passive optical and plasmonic devices with doped CdO spanning wavelengths from the ultraviolet to the mid‐infrared region.

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Gigahertz speed operation of epsilon-near-zero silicon photonic modulators

Cited by 101 publications

References 22 publications

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

High-harmonic generation from an epsilon-near-zero material

Broadband, High‐Speed, and Large‐Amplitude Dynamic Optical Switching with Yttrium‐Doped Cadmium Oxide

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