Plasmonic Modulators in Cryogenic Environment Featuring Bandwidths in Excess of 100 GHz and Reduced Plasmonic Losses.

Cryogenic quantum applications have a demand for an ever-higher number of interconnects and bandwidth. Photonic links are foreseen to offer data transfer with high bandwidth, low heat load, and low noise to enable the next-generation scalable quantum computing systems. However, they require high-speed and energy-efficient modulators operating at cryogenic temperatures for electro-optic signal conversion. Here, plasmonic organic electro-optic modulators operating at 4 K are demonstrated with a >100 GHz bandwidth, drive voltages as low as 96 mV, and a significant reduction in plasmonic propagation losses by over 40% compared to room temperature. Up to 160 Gbit/s and 256 Gbit/s cryogenic electro-optic signal conversion are demonstrated by performing data experiments using a plasmonic Mach-Zehnder modulator at around 1528 nm and a plasmonic ring-resonator modulator at around 1285 nm, respectively. This work shows that plasmonic modulators are ideally suited for future high-speed, scalable, and energy-efficient photonic interconnects in cryogenic environments.

100 GBd IM/DD transmission over 14†km SMF in the C-band enabled by a plasmonic SSB MZM.

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.

120 GBd plasmonic Mach-Zehnder modulator with a novel differential electrode design operated at a peak-to-peak drive voltage of 178 mV.

A new plasmonic Mach-Zehnder modulator is demonstrated at a bit rate of 120 Gb/s NRZ-OOK with low peak-to-peak driving voltages of 178 mVpp below the HD-FEC limit. Such record low driving voltage requirements potentially translate into an electrical drive power consumption of 862 aJ/bit. The low drive voltages have been made possible by a new differential Mach-Zehnder modulator electrode design. The differential electrode design is optimized for the balanced driving circuitry and reduces the effectively required driving voltage by a factor of four (Vπ/4). The potential of the transmitter scheme is further demonstrated by a transmission experiment over 500 m of single mode fiber at the C-band with a BER performance below the KP4 FEC limit.

Plasmonic IQ modulators with attojoule per bit electrical energy consumption.

Coherent optical communications provides the largest data transmission capacity with the highest spectral efficiency and therefore has a remarkable potential to satisfy today's ever-growing bandwidth demands. It relies on so-called in-phase/quadrature (IQ) electro-optic modulators that encode information on both the amplitude and the phase of light. Ideally, such IQ modulators should offer energy-efficient operation and a most compact footprint, which would allow high-density integration and high spatial parallelism. Here, we present compact IQ modulators with an active section occupying a footprint of 4 × 25 µm × 3 µm, fabricated on the silicon platform and operated with sub-1-V driving electronics. The devices exhibit low electrical energy consumptions of only 0.07 fJ bit-1 at 50 Gbit s-1, 0.3 fJ bit-1 at 200 Gbit s-1, and 2 fJ bit-1 at 400 Gbit s-1. Such IQ modulators may pave the way for application of IQ modulators in long-haul and short-haul communications alike.

High-speed plasmonic modulator in a single metal layer.

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.

Nonlinearities of organic electro-optic materials in nanoscale slots and implications for the optimum modulator design.

The performance of highly nonlinear organic electro-optic (EO) materials incorporated into nanoscale slots is examined. It is shown that EO coefficients as large as 190 pm/V can be obtained in 150 nm wide plasmonic slot waveguides but that the coefficients decrease for narrower slots. Possible mechanism that lead to such a decrease are discussed. Monte-Carlo computer simulations are performed, confirming that chromophore-surface interactions are one important factor influencing the EO coefficient in narrow plasmonic slots. These highly nonlinear materials are of particular interest for applications in optical modulators. However, in modulators the key parameters are the voltage-length product UπL and the insertion loss rather than the linear EO coefficients. We show record-low voltage-length products of 70 Vµm and 50 Vµm for slot widths in the order of 50 nm for the materials JRD1 and DLD164, respectively. This is because the nonlinear interaction is enhanced in narrow slot and thereby compensates for the reduced EO coefficient. Likewise, it is found that lowest insertion losses are observed for slot widths in the range 60 to 100 nm.

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.