Claudia Hoessbacher

Electrically Controlled Plasmonic Switches and Modulators

Plasmonic modulators and switches have recently attracted considerable attention because they offer ultracompact size, high bandwidths, and potentially low-power consumption. In this paper, we review and compare the current state of the art of plasmonic switches and discuss the various physical phenomena that are used to perform efficient switching. More precisely, we discuss plasmonic devices based on the thermal effect, the free carrier dispersion effect, the Pockels effect, phase change materials and switching caused by electrochemical metallization.

Direct Conversion of Free Space Millimeter Waves to Optical Domain by Plasmonic Modulator Antenna

A scheme for the direct conversion of millimeter and THz waves to optical signals is introduced. The compact device consists of a plasmonic phase modulator that is seamlessly cointegrated with an antenna. Neither high-speed electronics nor electronic amplification is required to drive the modulator. A built-in enhancement of the electric field by a factor of 35 000 enables the direct conversion of millimeter-wave signals to the optical domain. This high enhancement is obtained via a resonant antenna that is directly coupled to an optical field by means of a plasmonic modulator. The suggested concept provides a simple and cost-efficient alternative solution to conventional schemes where millimeter-wave signals are first converted to the electrical domain before being up-converted to the optical domain.

Plasmonic modulator with >170 GHz bandwidth demonstrated at 100 GBd NRZ

We demonstrate a plasmonic Mach-Zehnder (MZ) modulator with a flat frequency response exceeding 170 GHz. The modulator comprises two phase modulators exploiting the Pockels effect of an organic electro-optic material in plasmonic slot waveguides. We further show modulation at 100 GBd NRZ and 60 GBd PAM-4. The electrical drive signals were generated using a 100 GSa/s digital to analog converter (DAC). The high-speed and small-scale devices are relevant for next-generation optical interconnects.

High speed plasmonic modulator array enabling dense optical interconnect solutions

Plasmonic modulators might pave the way for a new generation of compact low-power high-speed optoelectronic devices. We introduce an extremely compact transmitter based on plasmonic Mach-Zehnder modulators offering a capacity of 4 × 36 Gbit/s on a footprint that is only limited by the size of the high-speed contact pads. The transmitter array is contacted through a multicore fiber with a channel spacing of 50 μm.

Plasmonic Organic Hybrid Modulators—Scaling Highest Speed Photonics to the Microscale

Complementing plasmonic slot waveguides with highly nonlinear organic materials has rendered a new generation of ultracompact active nanophotonic components that are redefining the state of the art. In this paper, we review the fundamentals of this so-called plasmonic- organic-hybrid (POH) platform. Starting from simple phase shifters to the most compact IQ modulators, we introduce key devices of high-speed data communications. For instance, all-plasmonic Mach-Zehnder modulators (MZMs) are reviewed and long-term prospects are discussed. This kind of modulator already features unique properties such as a small footprint (<; 20 μm2), a large electro-optic bandwidth (> 110 GHz), a small energy consumption (~25 fJ/b), a large extinction ratio (> 25 dB) in combination with a record small voltage-length product of 40 Vμm. Finally, as an example for seamless integration we introduce novel plasmonic IQ modulators. With such modulators we show the generation of advanced modulation formats (QPSK, 16-QAM) on footprints as small as 10 μm × 75 μm. This demonstration ultimately shows how plasmonics can be used to control both phase and amplitude of an optical carrier on the microscale with reasonably low losses.

High-speed plasmonic modulator in a single metal layer

Ultrafast plasmonic modulation Plasmonics converts light into propagating electrical signals. This approach could allow us to shrink optical components to the nanometer scale, far below the hundreds of wavelengths typically set by conventional optics. Ayata et al. fabricated a plasmonic modulator from a single layer of gold using a substrate-independent process. They created a device with a footprint less than the cross-sectional area of a human hair and with modulation rates exceeding 100 GHz, which could provide a flexible platform for future ultrafast plasmonic technology. Science, this issue p. 630 A high-speed, small-footprint plasmonic modulator is fabricated from a single layer of gold. Plasmonics provides a possible route to overcome both the speed limitations of electronics and the critical dimensions of photonics. We present an all-plasmonic 116–gigabits per second electro-optical modulator in which all the elements—the vertical grating couplers, splitters, polarization rotators, and active section with phase shifters—are included in a single metal layer. The device can be realized on any smooth substrate surface and operates with low energy consumption. Our results show that plasmonics is indeed a viable path to an ultracompact, highest-speed, and low-cost technology that might find many applications in a wide range of fields of sensing and communications because it is compatible with and can be placed on a wide variety of materials.

Digital Plasmonic Absorption Modulator Exploiting Epsilon-Near-Zero in Transparent Conducting Oxides

Optical switches operated around ε-near-zero (ENZ) of transparent conducting oxides (TCOs) are analyzed. A digital optical switching behavior is derived that is quite different from earlier predictions. The digital modulation characteristic originates from the fact that the nonlinear switching is, to a large extent, performed in the ENZ layer. The ENZ layer, however, arises from carrier accumulation in the TCO and is confined to a relatively thin layer with a characteristic dimension that does not change upon applying a higher voltage. An accurate treatment of this inhomogeneous layer is vital to reliably predict modulation characteristics. Such nonlinear accumulation processes and inhomogeneous material properties require refined simulations, which is why we apply an iterative solver based on a high-order finite-element method. More precisely, we solve the nonlinear stationary quantum hydrodynamic model to derive the carrier concentration upon applying an electrical field across the modulator. The result is then directly coupled to Maxwells equation, which shows a strong local enhancement of the electromagnetic fields in the ENZ layer. In an exemplary implementation, we forecast the feasibility of 6 μm long TCO absorption modulators with on-state losses of 2.8 dB and extinction ratios above 10 dB.

Ultra-compact plasmonic IQ-modulator

Plasmonic IQ-modulators with a record small footprint are demonstrated to operate up to 72 GBd. The devices have shown the ability to encode QPSK and 16-QAM modulation formats with power consumption as low as 27 fJ/bit at 18 GBd-16QAM.

Dense Plasmonic Mach-Zehnder Modulator Array for High-Speed Optical Interconnects

A plasmonic Mach-Zehnder modulator array with 4x36 Gbit/s capacity is introduced. The densely packed devices are connected by a multicore fiber demonstrating a highly scalable interconnect solution in a most compact footprint.

Broadband plasmonic modulator enabling single carrier operation beyond 100 Gbit/s

We demonstrate a plasmonic Mach-Zehnder modulator with a flat frequency response exceeding 170 GHz. Modulation of the device is shown at 100 GBd NRZ and 60 GBd PAM-4.