2,468 research outputs found
Nonlinear transmission lines for pulse shaping in silicon
Nonlinear transmission lines (NLTL) are used for pulse shaping. We developed the theory of pulse propagation through the NLTL. The problem of a wide pulse degenerating into multiple pulses rather than a single pulse is solved by using a gradually scaled NLTL. We exploit certain favorable properties of accumulation-mode MOS varactors to design an NLTL that can simultaneously sharpen both rising and falling edges. There is a good agreement among the theory, simulations, and measurements
Universal Three Dimensional Optical Logic
Modern integrated circuits are essentially two-dimensional (2D). Partial
three-dimensional (3D) integration and 3D-transistor-level integrated circuits
have long been anticipated as routes to improve the performance, cost and size
of electronic computing systems. Even as electronics approach fundamental
limits however, stubborn challenges in 3D circuits, and innovations in planar
technology have delayed the dimensional transition. Optical computing offers
potential for new computing approaches, substantially greater performance and
would complement technologies in optical interconnects and data storage.
Nevertheless, despite some progress, few proposed optical transistors possess
essential features required for integration into real computing systems. Here
we demonstrate a logic gate based on universal features of nonlinear wave
propagation: spatiotemporal instability and collapse. It meets the scaling
criteria and enables a 3D, reconfigurable, globally-hyperconnected architecture
that may achieve an exponential speed up over conventional platforms. It
provides an attractive building block for future optical computers, where its
universality should facilitate flexible implementations.Comment: manuscript (5 pages, 3 figures) with supplementary information (6
pages, 5 figures
Maximum-Likelihood Detection of Soliton with Timing Jitter
Using the maximum-likelihood detector (MLD) of a soliton with timing jitter
and noise, other than walk-out of the bit interval, timing jitter does not
degrade the performance of MLD. When the MLD is simulated with important
sampling method, even with a timing jitter standard deviation the same as the
full-width-half-maximum (FWHM) of the soliton, the signal-to-noise (SNR)
penalty is just about 0.2 dB. The MLD performs better than conventional scheme
to lengthen the decision window with additive noise proportional to the window
wide.Comment: 3 pages, 2 figures, submitted to Optics Letter
Cyclone Codes
We introduce Cyclone codes which are rateless erasure resilient codes. They
combine Pair codes with Luby Transform (LT) codes by computing a code symbol
from a random set of data symbols using bitwise XOR and cyclic shift
operations. The number of data symbols is chosen according to the Robust
Soliton distribution. XOR and cyclic shift operations establish a unitary
commutative ring if data symbols have a length of bits, for some prime
number . We consider the graph given by code symbols combining two data
symbols. If such random pairs are given for data symbols, then a
giant component appears, which can be resolved in linear time. We can extend
Cyclone codes to data symbols of arbitrary even length, provided the Goldbach
conjecture holds.
Applying results for this giant component, it follows that Cyclone codes have
the same encoding and decoding time complexity as LT codes, while the overhead
is upper-bounded by those of LT codes. Simulations indicate that Cyclone codes
significantly decreases the overhead of extra coding symbols
Perturbation of the sierpinski antenna to allocate the operating bands
A scheme for modifying the spacing between the bands of the Sierpinski antenna is introduced. Experimental results of two novel designs of fractal antennas suggest that the fractal structure can be perturbed to enable the log-period to be changed while still maintaining the multiband behaviour of the antenna.Peer ReviewedPostprint (published version
Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators
Recent advances in nonlinear optics have revolutionized integrated photonics, providing on-chip solutions to a wide range of new applications. Currently, state of the art integrated nonlinear photonic devices are mainly based on dielectric material platforms, such as Si₃N₄ and SiO₂. While semiconductor materials feature much higher nonlinear coefficients and convenience in active integration, they have suffered from high waveguide losses that prevent the realization of efficient nonlinear processes on-chip. Here, we challenge this status quo and demonstrate a low loss AlGaAs-on-insulator platform with anomalous dispersion and quality (Q) factors beyond 1.5 × 10⁶. Such a high quality factor, combined with high nonlinear coefficient and small mode volume, enabled us to demonstrate a Kerr frequency comb threshold of only ∼36 µW in a resonator with a 1 THz free spectral range, ∼100 times lower compared to that in previous semiconductor platforms. Moreover, combs with broad spans (>250 nm) have been generated with a pump power of ∼300 µW, which is lower than the threshold power of state-of the-art dielectric micro combs. A soliton-step transition has also been observed for the first time in an AlGaAs resonator
Hinge solitons in three-dimensional second-order topological insulators
A second-order topological insulator in three dimensions refers to a
topological insulator with gapless states localized on the hinges, which is a
generalization of a traditional topological insulator with gapless states
localized on the surfaces. Here we theoretically demonstrate the existence of
stable solitons localized on the hinges of a second-order topological insulator
in three dimensions when nonlinearity is involved. By means of systematic
numerical study, we find that the soliton has strong localization in real space
and propagates along the hinge unidirectionally without changing its shape. We
further construct an electric network to simulate the second-order topological
insulator. When a nonlinear inductor is appropriately involved, we find that
the system can support a bright soliton for the voltage distribution
demonstrated by stable time evolution of a voltage pulse.Comment: 11 pages, 6 figure
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