170 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
Characterizing photonic crystal waveguides with an expanded k-space evanescent coupling technique
We demonstrate a direct, single measurement technique for
characterizing the dispersion of a photonic crystal waveguide (PCWG)
using a tapered fiber evanescent coupling method. A highly curved fiber
taper is used to probe the Fabry-PĂ©rot spectrum of a closed PCWG over a
broad k-space range, and from this measurement the dispersive properties of
the waveguide can be found. Waveguide propagation losses can also be
estimated from measurements of closed waveguides with different lengths.
The validity of this method is demonstrated by comparing the results
obtained on a âW1â PCWG in chalcogenide glass with numerical
simulation
High quality waveguides for the mid-infrared wavelength range in a silicon-on-sapphire platform
We report record low loss silicon-on-sapphire nanowires for applications to
mid infrared optics. We achieve propagation losses as low as 0.8dB/cm at
1550nm, 1.1 to 1.4dB/cm at 2080nm and < 2dB/cm at = 5.18 microns.Comment: 9 pages, 6 figures, 18 reference
Characteristics of Correlated Photon Pairs Generated in Ultra-compact Silicon Slow-light Photonic Crystal Waveguides
We report the characterization of correlated photon pairs generated in
dispersion-engineered silicon slow-light photonic crystal waveguides pumped by
picosecond pulses. We found that taking advantage of the 15 nm flat-band
slow-light window (vg ~ c/30) the bandwidth for correlated photon-pair
generation in 96 and 196 \mum long waveguides was at least 11.2 nm; while a 396
\mum long waveguide reduced the bandwidth to 8 nm (only half of the slow-light
bandwidth due to the increased impact of phase matching in a longer waveguide).
The key metrics for a photon-pair source: coincidence to accidental ratio (CAR)
and pair brightness were measured to be a maximum 33 at a pair generation rate
of 0.004 pair per pulse in a 196 \mum long waveguide. Within the measurement
errors the maximum CAR achieved in 96, 196 and 396 \mum long waveguides is
constant. The noise analysis shows that detector dark counts, leaked pump
light, linear and nonlinear losses, multiple pair generation and detector
jitter are the limiting factors to the CAR performance of the sources.Comment: 8 pages, 7 figure
Frontiers in microphotonics: tunability and all-optical control
The miniaturization of optical devices and their integration for creating adaptive and reconfigurable photonic integrated circuits requires effective platforms and methods to control light over very short distances. We present here several techniques an
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