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  1. Congreve, Daniel ; Nielsen, Christian ; Musser, Andrew J. ; Baran, Derya (Ed.)
    Hybrid organic electro-optic (OEO) devices consist of a layer of ordered organic chromophores confined between layers of metals or semiconductors, enabling optical fields to be tightly confined within the OEO material. The combination of tight confinement with the high electro-optic (EO) performance of state-of-the art OEO materials enables exceptional electro-optic switching performance in silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) device architectures. Recent records in POH devices include bandwidths > 500 GHz and energy efficiency < 100 aJ/bit. However, optimization of device performance requires both understanding and improving the degree to which chromophores can be acentrically ordered near a metal or semiconductor interface. Applying bulk and/or isotropic models of OEO materials to nanophotonic device architectures often lead to overly optimistic translation of materials performance to device performance. Prior work has identified influences of high centrosymmetric order (birefringence), altered relations between acentric and centrosymmetric order (dimensionality), and surface electrostatics on chromophore ordering. We combine these models into a representation that can be used to understand the influences of these phenomena on device performance, how some prior OEO materials exhibited unusually high performance under confinement, how ordering close to surfaces may be improved, and implications for future electro-optic device design.
  2. Abstract

    Tailored nanostructures provide at-will control over the properties of light, with applications in imaging and spectroscopy. Active photonics can further open new avenues in remote monitoring, virtual or augmented reality and time-resolved sensing. Nanomaterials withχ(2)nonlinearities achieve highest switching speeds. Current demonstrations typically require a trade-off: they either rely on traditionalχ(2)materials, which have low non-linearities, or on application-specific quantum well heterostructures that exhibit a highχ(2)in a narrow band. Here, we show that a thin film of organic electro-optic molecules JRD1 in polymethylmethacrylate combines desired merits for active free-space optics: broadband record-high nonlinearity (10-100 times higher than traditional materials at wavelengths 1100-1600 nm), a custom-tailored nonlinear tensor at the nanoscale, and engineered optical and electronic responses. We demonstrate a tuning of optical resonances by Δλ = 11 nm at DC voltages and a modulation of the transmitted intensity up to 40%, at speeds up to 50 MHz. We realize 2 × 2 single- and 1 × 5 multi-color spatial light modulators. We demonstrate their potential for imaging and remote sensing. The compatibility with compact laser diodes, the achieved millimeter size and the low power consumption are further key features for laser ranging or reconfigurable optics.

  3. Sekkat, Zouheir ; Omatsu, Takashige (Ed.)
    We review recent transformative advances in materials design, synthesis, and processing as well as device engineering for the utilization of organic materials in hybrid electro-optic (EO) and optical rectification (OR) technologies relevant to telecommunications, sensing, and computing. End-to-end (from molecules to systems) modeling methods utilizing multi-scale computation and theory permit prediction of the performance of novel materials in nanoscale device architectures including those involving plasmonic phenomena and architectures in which interfacial effects play a dominant role. Both EO and OR phenomenon require acentric organization of constituent active molecules. The incumbent methodology for achieving such organization is electric field poling, where chromophore shape, dipole moment, and conformational flexibility play dominant roles. Optimized chromophore design and control of the poling process has already led to record-setting advances in electro-optic performance, e.g., voltage-length performance of < 50 volt-micrometer, bandwidths > 500 GHz, and energy efficiency < 70 attojoule/bit. They have also led to increased thermal stability, low insertion loss and high signal quality (BER and SFDR). However, the limits of poling in the smallest nanophotonic devices—in which extraordinary optical field densities can be achieved—has stimulated development of alternatives based on covalent coupling of modern high-performance chromophores into ordered nanostructures. Covalent coupling enables highermore »performance, greater scalability, and greater stability and is especially suited for the latest nanoscale architectures. Recent developments in materials also facilitate a new technology—transparent photodetection based on optical rectification. OR does not involve electronic excitation, as is the case with conventional photodiodes, and as such represents a novel detection mechanism with a greatly reduced noise floor. OR already dominates at THz frequencies and recent advances will enable superior performance at GHz frequencies as well.« less
  4. Organic electro-optic (EO) materials incorporated into silicon-organic hybrid and plasmonic-organic hybrid devices have enabled new records in EO modulation performance. We report a new series of nonlinear optical chromophores engineered by theory-guided design, utilizing bis(4-dialkylaminophenyl)heteroarylamino donor moieties to greatly enhance molecular hyperpolarizabilities. Hyperpolarizabilities predicted using density functional theory were validated by hyper-Rayleigh scattering measurements, showing strong prediction/experiment agreement and >2-fold advancement in static hyperpolarizability over the best prior chromophores. Electric field poled thin films of these chromophores showed significantly enhanced EO coefficients ( r 33 ) and poling efficiencies ( r 33 / E p ) at low chromophore concentrations compared with state-of-the-art chromophores such as JRD1 . The highest performing blend, containing just 10 wt% of the novel chromophore BTP7 , showed a 12-fold enhancement in poling efficiency per unit concentration vs. JRD1 . Our results suggest that further improvement in chromophore hyperpolarizability is feasible without unacceptable tradeoffs with optical loss or stability.
  5. Electro-optic (EO) modulators rely on the interaction of optical and electrical signals with second-order nonlinear media. For the optical signal, this interaction can be strongly enhanced using dielectric slot–waveguide structures that exploit a field discontinuity at the interface between a high-index waveguide core and the low-index EO cladding. In contrast to this, the electrical signal is usually applied through conductive regions in the direct vicinity of the optical waveguide. To avoid excessive optical loss, the conductivity of these regions is maintained at a moderate level, thus leading to inherentRClimitations of the modulation bandwidth. In this paper, we show that these limitations can be overcome by extending the slot–waveguide concept to the modulating radio-frequency (RF) signal. Our device combines an RF slotline that relies onBaTiO3as a high-k dielectric material with a conventional silicon photonic slot waveguide and a highly efficient organic EO cladding material. In a proof-of-concept experiment, we demonstrate a 1 mm long Mach–Zehnder modulator that offers a 3 dB bandwidth of 76 GHz and a 6 dB bandwidth of 110 GHz along with a smallπ<#comment/>voltage of 1.3 V (Uπ<#comment/>L=1.3Vmm). Wemore »further demonstrate the viability of the device in a data-transmission experiment using four-state pulse-amplitude modulation (PAM4) at line rates up to 200 Gbit/s. Our first-generation devices leave vast room for further improvement and may open an attractive route towards highly efficient silicon photonic modulators that combine sub-1 mm device lengths with sub-1 V drive voltages and modulation bandwidths of more than 100 GHz.

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  6. Electro-optic quantum coherent interfaces map the amplitude and phase of a quantum signal directly to the phase or intensity of a probe beam. At terahertz frequencies, a fundamental challenge is not only to sense such weak signals (due to a weak coupling with a probe in the near-infrared) but also to resolve them in the time domain. Cavity confinement of both light fields can increase the interaction and achieve strong coupling. Using this approach, current realizations are limited to low microwave frequencies. Alternatively, in bulk crystals, electro-optic sampling was shown to reach quantum-level sensitivity of terahertz waves. Yet, the coupling strength was extremely weak. Here, we propose an on-chip architecture that concomitantly provides subcycle temporal resolution and an extreme sensitivity to sense terahertz intracavity fields below 20 V/m. We use guided femtosecond pulses in the near-infrared and a confinement of the terahertz wave to a volume ofVTHz∼<#comment/>10−<#comment/>9(λ<#comment/>THz/2)3in combination with ultraperformant organic molecules (r33=170pm/V) and accomplish a record-high single-photon electro-optic coupling rate ofgeo=2π<#comment/>×<#comment/>0.043Gmore »mathvariant='normal'>Hz, 10,000 times higher than in recent reports of sensing vacuum field fluctuations in bulk media. Via homodyne detection implemented directly on chip, the interaction results into an intensity modulation of the femtosecond pulses. The single-photon cooperativity isC0=1.6×<#comment/>10−<#comment/>8, and the multiphoton cooperativity isC=0.002at room temperature. We show><#comment/>70dBdynamic range in intensity at 500 ms integration under irradiation with a weak coherent terahertz field. Similar devices could be employed in future measurements of quantum states in the terahertz at the standard quantum limit, or for entanglement of subsystems on subcycle temporal scales, such as terahertz and near-infrared quantum bits.

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  7. 100 Gb/s NRZ-OOK transmission over 14 km standard single mode fiber in the C-band is demonstrated with a simple intensity modulation and direct detection scheme. The transmission concept utilizes single sideband modulation and comprises a single differential digital-to-analog converter with adjustable phase offset, a new dual electrode plasmonic Mach-Zehnder modulator, a laser at 1537.5 nm, standard single mode fibers, a photodiode, an analog-to-digital converter, and linear offline digital signal processing. The presented SSB concept requires no DSP and complex signaling at the transmitter. The demonstrated SSB transmitter increased the possible transmission distance by a factor of 4.6 compared to a DSB transmitter. We also investigated the equalization requirements. A T/2-spaced feedforward equalizer requires 27 taps to achieve transmission over 10 km with a BER below the HD-FEC limit. In comparison to a DSB transmitter, the SSB transmitter reduced the receiver DSP complexity by a factor of 13.7.