1,720,971 research outputs found
Upconversion detection of 1.25 Gb/s mid-infrared telecommunications using a silicon avalanche photodiode
No full textWith an ever-increasing interest in secure and reliable free-space optical communication, upconversion detectors enabled through nonlinear optical processes are an attractive route to transmitting data as a mid-infrared signal. This spectral region is known to have a higher transmissivity through the atmosphere. In this work, we present an upconversion scheme for detection in the silicon absorption band using magnesium-oxide doped periodically poled lithium niobate to generate 20 mW of a 3.4~µm signal from commercial laser sources using a difference frequency generation process. Following a further nonlinear frequency conversion, via sum-frequency generation, the resulting signal at 809~nm is detected. We achieve >50 µW of signal and bit error rates of 10-7 from a single-pass nonlinear conversion for both the transmitter and receiver systems without the need for additional optical amplifiers at the receiving end. The error rates due to potentially reduced laser powers at the receiver end are investigated and laser noise transfer through our system is discussed
Dataset for thesis: 'UV Written Blazed Chirped Bragg Grating Spectrometers'
No full textRaw experimental data for University of Southampton Doctoral Thesis. Spectral data for waveguides used to estimate wafer parameters, as well as images of the output of fabricated spectrometers under wavelength tuning.</span
Dataset for 'Upconversion detection of 1.25 Gb/s mid-infrared telecommunications using a silicon avalanche photodiode'
No full textThis dataset supports the publication:
Alan C. Gray, Sam A. Berry, Lewis G. Carpenter, James C. Gates, Corin B. E. Gawith, and Peter G. R. Smith, "Upconversion detection of 1.25 Gb/s mid-infrared telecommunications using a silicon avalanche photodiode," Optics Express 28, 34279-34289 (2020), https://dx.doi.org/10.1364/OE.404855
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CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm
No full textPeriodically poled lithium niobate (PPLN) waveguides are a proven and popularmeans for efficient wavelength conversion. However, conventional PPLN waveguides typically have small mode field diameters (MFD) (≲6µm) or significant insertion and/or propagation losses, limiting their ability to operate at multi-watt power levels. In this work we utilise zinc indiffused PPLN ridge waveguides that have a larger MFD, favourable pump/SHG modal overlap, and low insertion losses. Here for the first time, we have demonstrated continuous wave (CW) spectral narrowing from a PPLN waveguide; both with high efficiency and multi-watt second harmonic generation (SHG). 2.5 W of 780 nm has been produced by SHG of an amplified 1560 nm telecom laser with a device efficiency of 58% in a 4.0 cm-long ridge waveguide. We have modelled conversion efficiency and applied experimentally measured waveguide parameters to show excellent agreement to the SHG spectra. Spectral narrowing of the full width half maximum (FWHM) of 35.7% has been measured as the nonlinear drive is increased. This work demonstrates that single-pass, multi-watt, CW SHG at 780 nm is feasible from our PPLN waveguide in the large conversion regime
Dataset for: CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm
No full textDataset supports: Carpenter, L. G., Berry, S. A., Gray, A. C., Gates, J., Smith, P. G. R., & Gawith, C. (2020). CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm. Optics Express, 28(15), 21382-21390.</span
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Upconversion detection of 1.25 Gb/s Mid-IR telecommunications using a silicon avalanche photodiode
No full textWe present our current work investigating telecommunication transmission in the mid-infrared region and detection in the silicon absorption band. We achieve 10-7 bit error rates using commercial lasers in single-pass nonlinear conversion stages using MgO:PPLN
Terahertz focusing and polarization control in large-area bias-free semiconductor emitters
No full textWe show that, when large-area multiplex terahertz semiconductor emitters, that work on diffusion currents and Schottky potentials, are illuminated by ultrashort optical pulses they can radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near-infrared pulse, we have demonstrated THz emission focusing in free space, at the same point where the optical radiation would focus. We investigated the beam waist and Gouy phase shift of the THz emission as a function of frequency. We also show that the polarization profile of the emitted THz can be tailored by the metallic patterning on the semiconductor, demonstrating radial polarization when a circular emitter design is used. Our techniques can be used for fast THz beam steering and mode control for efficiently coupling to waveguides without the need for THz lenses or parabolic mirrors.</p
Highly-chirped Bragg gratings for integrated silica spectrometers
No full textA blazed chirped Bragg grating in a planar silica waveguide device was used to create an integrated diffractive element for a spectrometer. The grating diffracts light from a waveguide and creates a wavelength dependent focus in a manner similar to a bulk diffraction grating spectrometer. An external imaging system is used to analyse the light, later device iterations plan to integrate detectors to make a fully integrated spectrometer. Devices were fabricated with grating period chirp rates in excess of 100nm/mm, achieving a focal length of 5.5 mm. Correction of coma aberrations resulted in a device with a footprint of 20 mm x 10mm, a peak FWHM resolution of 1.8 nm, a typical FWHM resolution of 2.6 nm and operating with a 160 nm bandwidth centered at 1550 nm.<br/
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