3,195 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
Two-photon interference between disparate sources for quantum networking
Quantum networks involve entanglement sharing between multiple users.
Ideally, any two users would be able to connect regardless of the type of
photon source they employ, provided they fulfill the requirements for
two-photon interference. From a theoretical perspective, photons coming from
different origins can interfere with a perfect visibility, provided they are
made indistinguishable in all degrees of freedom. Previous experimental
demonstrations of such a scenario have been limited to photon wavelengths below
900 nm, unsuitable for long distance communication, and suffered from low
interference visibility. We report two-photon interference using two disparate
heralded single photon sources, which involve different nonlinear effects,
operating in the telecom wavelength range. The measured visibility of the
two-photon interference is 80+/-4%, which paves the way to hybrid universal
quantum networks
Photon Counting and Direct ToF Camera Prototype Based on CMOS SPADs
This paper presents a camera prototype for 2D/3D image capture in low illumination conditions based on single-photon avalanche-diode (SPAD) image sensor for direct time-offlight (d-ToF). The imager is a 64×64 array with in-pixel TDC for high frame rate acquisition. Circuit design techniques are combined to ensure successful 3D image capturing under low sensitivity conditions and high level of uncorrelated noise such as dark count and background illumination. Among them an innovative time gated front-end for the SPAD detector, a reverse start-stop scheme and real-time image reconstruction at Ikfps are incorporated by the imager. To the best of our knowledge, this is the first ToF camera based on a SPAD sensor fabricated and proved for 3D image reconstruction in a standard CMOS process without any opto-flavor or high voltage option. It has a depth resolution of 1cm at an illumination power from less than 6nW/mm 2 down to 0.1nW/mm 2 .Office of Naval Research (USA) N000141410355Ministerio de Economía y Competitividad TEC2015-66878-C3- 1-RJunta de Andalucía P12-TIC 233
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