33,518 research outputs found
Ultra-compact optical auto-correlator based on slow-light enhanced third harmonic generation in a silicon photonic crystal waveguide
The ability to use coherent light for material science and applications is
directly linked to our ability to measure short optical pulses. While
free-space optical methods are well-established, achieving this on a chip would
offer the greatest benefit in footprint, performance, flexibility and cost, and
allow the integration with complementary signal processing devices. A key goal
is to achieve operation at sub-Watt peak power levels and on sub-picosecond
timescales. Previous integrated demonstrations require either a temporally
synchronized reference pulse, an off-chip spectrometer, or long tunable delay
lines. We report the first device capable of achieving single-shot time-domain
measurements of near-infrared picosecond pulses based on an ultra-compact
integrated CMOS compatible device, with the potential to be fully integrated
without any external instrumentation. It relies on optical third-harmonic
generation in a slow-light silicon waveguide. Our method can also serve as a
powerful in-situ diagnostic tool to directly map, at visible wavelengths, the
propagation dynamics of near-infrared pulses in photonic crystals.Comment: 20 pages, 6 figures, 38 reference
Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides
All-optical signal processing is envisioned as an approach to dramatically
decrease power consumption and speed up performance of next-generation optical
telecommunications networks. Nonlinear optical effects, such as four-wave
mixing (FWM) and parametric gain, have long been explored to realize
all-optical functions in glass fibers. An alternative approach is to employ
nanoscale engineering of silicon waveguides to enhance the optical
nonlinearities by up to five orders of magnitude, enabling integrated
chip-scale all-optical signal processing. Previously, strong two-photon
absorption (TPA) of the telecom-band pump has been a fundamental and
unavoidable obstacle, limiting parametric gain to values on the order of a few
dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier
exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near
one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic
TPA-related absorption vanishes. This gain is high enough to compensate all
insertion losses, resulting in 13 dB net off-chip amplification. Furthermore,
dispersion engineering dramatically increases the gain bandwidth to more than
220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its
significant relevance to all-optical signal processing, the broadband
parametric gain also facilitates the simultaneous generation of multiple
on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range.
Together, these results provide a foundation for the construction of
silicon-based room-temperature mid-IR light sources including tunable
chip-scale parametric oscillators, optical frequency combs, and supercontinuum
generators
Coherent terabit communications with microresonator Kerr frequency combs
Optical frequency combs enable coherent data transmission on hundreds of
wavelength channels and have the potential to revolutionize terabit
communications. Generation of Kerr combs in nonlinear integrated microcavities
represents a particularly promising option enabling line spacings of tens of
GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr
combs may exhibit strong phase noise and multiplet spectral lines, and this has
made high-speed data transmission impossible up to now. Recent work has shown
that systematic adjustment of pump conditions enables low phase-noise Kerr
combs with singlet spectral lines. Here we demonstrate that Kerr combs are
suited for coherent data transmission with advanced modulation formats that
pose stringent requirements on the spectral purity of the optical source. In a
first experiment, we encode a data stream of 392 Gbit/s on subsequent lines of
a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature
amplitude modulation (16QAM). A second experiment shows feedback-stabilization
of a Kerr comb and transmission of a 1.44 Tbit/s data stream over a distance of
up to 300 km. The results demonstrate that Kerr combs can meet the highly
demanding requirements of multi-terabit/s coherent communications and thus
offer a solution towards chip-scale terabit/s transceivers
Boundary effects in finite size plasmonic crystals: Focusing and routing of plasmonic beams for optical communications
Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and associated beam parameters such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components
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