23 research outputs found
All-optical 2R regeneration using the hysteresis in a distributed feedback laser diode
A broadband optical 2R regenerator based on a single distributed feedback laser is demonstrated for nonreturn to zero signals at a bitrate of 10 Gb/s. A semi-analytical approach for the influence of hysteresis on the transfer function of a 2R regenerator is shown
Compact and scalable polarimetric self-coherent receiver using dielectric metasurface
The polarimetric self-coherent system using a direct-detection-based
Stokes-vector receiver (SVR) is a promising technology to meet both the cost
and capacity requirements of the short-reach optical interconnects. However,
conventional SVRs require a number of optical components to detect the state of
polarization at high speed, resulting in substantially more complicated
receiver configurations compared with the current
intensity-modulation-direct-detection (IMDD) counterparts. Here, we demonstrate
a simple and compact polarimetric self-coherent receiver based on a thin
dielectric metasurface and a photodetector array (PDA). With a single
1.05-m-thick metasurface device fabricated on a compact silicon-on-quartz
chip, we implement functionalities of all the necessary passive components: a
13 splitter, three polarization beam splitters with different
polarization bases, and six focusing lenses. Combined with a high-speed PDA, we
demonstrate self-coherent transmission of 20-GBd 16-ary quadrature amplitude
modulation (16QAM) and 50-GBd quadrature phase-shift keying (QPSK) signals over
a 25-km single-mode fiber. Owing to the surface-normal configuration, it can
easily be scaled to receive spatially multiplexed channels from a multicore
fiber or a fiber bundle, enabling compact and low-cost receiver modules for the
future highly parallelized self-coherent systems.Comment: 10 pages, 6 figures (main manuscript) + 2 pages, 2 figures
(supplementary info
High-speed metasurface modulator using critically coupled bimodal plasmonic resonance
Free-space electro-optic (EO) modulators operating at gigahertz and beyond
are attractive for a wide range of emerging applications, including high-speed
imaging, free-space optical communication, microwave photonics, and diffractive
computing. Here we experimentally demonstrate a high-speed plasmonic
metasurface EO modulator operating at a near-infrared wavelength range with a
gigahertz modulation bandwidth. To achieve efficient intensity modulation of
reflected light from an ultrathin metasurface layer, we utilize the bimodal
plasmonic resonance inside a subwavelength metal-insulator-metal grating, which
is precisely tuned to satisfy the critical coupling condition. As a result,
perfect absorption of -27 dB (99.8%) and a high quality (Q) factor of 113 are
obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer
inside the grating, we achieve a modulation depth of up to 9.5 dB under an
applied voltage of 30 V. The 3-dB modulation bandwidth is confirmed to be
1.25 GHz, which is primarily limited by the undesired contact resistance. Owing
to the high electrical conductivity of metallic gratings and a compact device
structure with a minimal parasitic capacitance, the demonstrated device can
potentially operate at several tens of gigahertz, which opens up exciting
opportunities for ultrahigh-speed active metasurface devices in various
applications.Comment: Main text: 18 pages, 3 figures, 39 references Supplementary material:
3 pages, 2 figures
Ultra-broadband surface-normal coherent optical receiver with nanometallic polarizers
A coherent receiver that can demodulate high-speed in-phase and quadrature
signals of light is an essential component for optical communication,
interconnects, imaging, and computing. Conventional waveguide-based coherent
receivers, however, exhibit large footprints, difficulty in coupling a large
number of spatial channels efficiently, and limited operating bandwidth imposed
by the waveguide-based optical hybrid. Here, we present a surface-normal
coherent receiver with nanometallic-grating-based polarizers integrated
directly on top of photodetectors without the need for an optical hybrid
circuit. Using a fabricated device with the active section occupying a
70-{\mu}m-square footprint, we demonstrate demodulation of high-speed (up to 64
Gbaud) coherent signals in various formats. Moreover, ultra-broadband operation
from 1260 nm to 1630 nm is demonstrated, thanks to the wavelength-insensitive
nanometallic polarizers. To our knowledge, this is the first demonstration of a
surface-normal homodyne optical receiver, which can easily be scaled to a
compact two-dimensional arrayed device to receive highly parallelized coherent
signals.Comment: 23 pages, 4 figures (main manuscript) + 4 pages, 2 figures
(supporting info
Compact photonic crystal disk cavity optimized using the gentle confinement method and boundary design
A compact, novel photonic crystal cavity aimed at applications with strict area limitations is presented. Optimization shows that the gentle confinement method previously used for line-defect cavities can be applied to more limited geometries. It also shows that it is paramount to consider the boundary region to minimize in-plane losses. The investigation show that a near optimum boundary thickness can be found by considering the boundary region as a Fabry-Pérot resonator. This optimization strategy is shown to be deterministic in terms of resonance wavelength. For an optimized air-clad, silicon cavity, finite-difference time-domain simulations give Q-values as high as 75,000 which is comparable to other photonic crystal cavities of similar size
40-Gb/s All-optical packet switching with a distributed-feedback laser as all-optical flip-flop
All-optical flip-flops (AOFFs) have recently received increased attention as elements for all-optical packet-switched networks. In this letter, we use a single off-the-shelf distributed-feedback laser as AOFF to switch 40-Gb/s packets with a guard time as low as 150 ps