Pier Sazio

University of Southampton, Southampton, England, United Kingdom

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Publications (82)351.68 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The ability to manipulate a single quantum object, such as a single electron or a single spin, to induce a change in a macroscopic observable lies at the heart of nano-devices of the future. We report an experiment wherein a single superconducting flux quantum, or a fluxon, can be exploited to switch the resistance of a nanowire between two discrete values. The experimental geometry consists of centimeter-long nanowires of superconducting Ga-In eutectic, with spontaneously formed Ga nanodroplets along the length of the nanowire. The nonzero resistance occurs when a Ga nanodroplet traps one or more superconducting fluxons, thereby driving a Josephson weak-link created by a second nearby Ga nanodroplet normal. The fluxons can be inserted or flipped by careful manipulation of the magnetic field or temperature, to produce one of many metastable states of the system.
    Nano Letters 11/2014; · 12.94 Impact Factor
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    ABSTRACT: Conventional thermal poling methods require direct physical contact to internal fiber electrodes. Here, we report an indirect electrostatic induction technique using electrically floating wires inside the fiber combined with external electric fields that can allow for facile poling of complex microstructured fibers (MOFs) of arbitrarily long lengths. In combination with our unique ability to use liquid gallium electrodes, inducing second-order nonlinearities inside otherwise difficult to access multi-core or multi-hole MOFs now becomes entirely feasible and practical. The formation of a permanent second-order nonlinearity is unequivocally demonstrated by realizing quasi-phase-matched frequency doublers using periodic UV erasure methods in the induction-poled fibers. The second-order susceptibility created inside the fiber is driven by the potential difference established between the floating electrodes, which we calculate via numerical simulations.
    Optics Letters 11/2014; 39(22). · 3.39 Impact Factor
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    ABSTRACT: For decades now, silicon has been the workhorse of the microelectronics revolution and a key enabler of the information age. Owing to its excellent optical properties in the near-and mid-infrared, silicon is now promising to have a similar impact on photonics. The ability to incorporate both optical and electronic functionality in a single material offers the tantalizing prospect of amplifying, modulating and detecting light within a monolithic platform. However, a direct consequence of silicon's transparency is that it cannot be used to detect light at telecommunications wavelengths. Here, we report on a laser processing technique developed for our silicon fibre technology through which we can modify the electronic band structure of the semiconductor material as it is crystallized. The unique fibre geometry in which the silicon core is confined within a silica cladding allows large anisotropic stresses to be set into the crystalline material so that the size of the bandgap can be engineered. We demonstrate extreme bandgap reductions from 1.11 eV down to 0.59 eV, enabling optical detection out to 2,100 nm.
    Nature Material 09/2014; 13:1122-1127. · 36.43 Impact Factor
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    ABSTRACT: A laser processing method for tuning the size of the anisotropic strain in a silicon core optical fiber is demonstrated. This technique can be used to modify the core’s opto-electronic properties for specific requirements.
    Bragg Gratings, Photosensitivity, and Poling in Glass Waveguides; 01/2014
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    ABSTRACT: Conventional thermal poling methods require direct physical contact to internal fibers electrodes. Here, we report a novel indirect method in which external fields are used to charge floating internal electrodes to generate depletion regions for SHG.
    Bragg Gratings, Photosensitivity, and Poling in Glass Waveguides; 01/2014
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    ABSTRACT: The state of the art of silicon optical fibers fabricated via the high pressure chemical deposition technique will be reviewed. The optical transmission properties of step index silicon optical fibers will be presented. In addition, alternative complex fiber geometries that permit sophisticated control of the propagating light will be introduced.
    Asia Communications and Photonics Conference; 11/2013
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    ABSTRACT: form only given. Semiconductor core optical fibres offer the exciting prospect of performing non-linear optics and signal processing in a geometry that is inherently compatible with today's fibre optical networks. To fully exploit the potential of these fibres it is important that they can be fabricated with core sizes of the order of 1 μm, or less, so as to enhance their non-linear optical parameter and facilitate low loss integration with standard fibres. In this paper we report on the fabrication of such fibres and present a route to improving the material quality, and hence reducing the losses, via laser annealing [1]. Amorphous silicon (a-Si) optical fibres with core sizes ranging in diameter from 0.8 - 1.7 μm were fabricated using the well-established high pressure microfluidic chemical deposition technique [2]. The micro-Raman spectrum for the as-deposited core material is shown in Fig 1(a) and clearly demonstrates the characteristic broad peak of a-Si at 480 cm-1. The losses of this material are typically as high as 50 dB/cm, and it is therefore unsuitable for the fabrication of the majority of optical devices. To improve the transmission properties, a CW argon ion laser operating at 488 nm and a power of - 2 W was focused onto the core to anneal the material to a crystalline phase. The photon energy at this wavelength is - 2.5 eV which is much greater than the indirect band-gap energy of silicon, 1.1 eV. Thus the photons are strongly absorbed and generate a plasma of free electrons that causes the core to heat up via phonon assisted recombination. A set of high precision stages were used to ensure that the core was kept at the laser's focal point whilst being scanned through the beam. The Raman spectra of an annealed fibre and a single crystal reference are juxtaposed in Fig. 1(b). The difference in peak position for the fibre core spectrum is a consequence of the residual stress associated with the mismatch between the thermal ex- ansion coefficients of the silica cladding and the silicon core materials. Voigt fitting of the spectra shows that they both have a Lorentzian component with a linewidth of 2.7 cm-1, indicating a highly crystalline core material. The optical transmission loss of this annealed silicon optical fibre was measured at an operating wavelength of 1550 nm to be 5.6 dB/cm over a 1mm length, representing the lowest loss that has been reported for a crystalline silicon optical fibre with a sub-micron radius core. Subsequent TEM measurements revealed that large millimetre scale single crystal sections of core material were produced using this technique. We will discuss our efforts to increase the annealed core to a length that is suitable for practical device fabrication, as evidenced by the consistent Raman spectral width measured over 13 mm in Fig. 1(c). We anticipate that this work will lead to the development of in-fibre semiconductor devices that can be seamlessly integrated with the standard single mode fibres found in today's optical networks.
    The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: Deposition techniques that can uniformly and conformally coat deep trenches and very high aspect ratio pores with uniform thickness films are valuable in the synthesis of complex three-dimensionally structured materials. Here it is shown that high pressure chemical vapor deposition can be used to deposit conformal films of II–VI semiconductors such as ZnSe, ZnS, and ZnO into high aspect ratio pores. Microstructured optical fibers serve as tailored templates for the patterning of II–VI semiconductor microwire arrays of these materials with precision and flexibility. In this way, centimeters-long microwires with exterior surfaces that conform well to the nearly atomically smooth silica templates can be fabricated by conformal coating. This process allows for II–VI semiconductors, which cannot be processed into optical fibers with conventional techniques, to be fabricated into step index and microstructured optical fibers.
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    ABSTRACT: John V. Badding and co-workers demonstrate on p. 1461 the ability to fabricate silicon p-i-n junctions within high aspect ratio optical fibers, and which exhibit photovoltaic response. These structures are flexible, even when removed from their silica glass templates, despite their crystalline nature. Junctions of up to one meter ength have been fabricated, but also a Si wire with a length of over 10 meters has been made. This Si wire can be wound onto a spool and even woven into a fabric. With further development, these fibers can be useful for textiles and other woven fabric applications.
    Advanced Materials 03/2013; 25(10):1460. · 15.41 Impact Factor
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    ABSTRACT: In-doped Ga nanowires 150 nm in diameter and 6mm in length have been formed in silica nanocapillaries. X-ray fluorescence and diffraction measurements performed at the Advanced Photon Source have been used to characterize their chemical composition and crystal structure. Investigation of the low temperature transport properties of these wires reveals a two stage superconducting transition. Magnetoresistance measurements are suggestive of vortex trapping in the wire. The X-ray fluorescence measurements suggest phase separation in the capillaries into Ga nanodroplets and In-Ga eutectic wires. A model to explain the vortex trapping consistent with this observation is being developed.
    03/2013;
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    ABSTRACT: Superfluidity, as superconductivity, cannot exist in a strict one-dimensional system. However, the experiments employing porous media showed that superfluid helium can flow through the pores of nanometer size. Here we report a study of the flow of liquid helium through a single hollow glass fiber of 4 cm in length with an open id of 150 nm between 1.6 and 2.3 K. We found the superfluid transition temperature was suppressed in the hollow cylinder and that there is no flow above the transition. Critical velocity at temperature below the transition temperature was determined. Our results bear some similarity to that found by Savard et. al. [1] studying the flow of helium through a nanohole in a silicon nitrite membrane.[1] M. Savard, G. Dauphinais, and G. Gervais, Phys. Rev. Lett. 107, 254501 (2011)
    03/2013;
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    ABSTRACT: The paper reports on pursing a different, potentially complementary vision of all-fiber optoelectronics in which light can be generated, modulated, and detected within the fiber itself. Fiber devices are in general valued for their robustness, simplicity, and ability to integrate seamlessly with existing fiber infrastructure. If the light never leaves the fiber, for example, difficulties associated with modal and impedance mismatches between fibers and planar semiconductor waveguides do not need to be overcome. Fiber lasers also integrate naturally with fibers, whereas using direct gap semiconductor lasers on chip remains an ongoing challenge. Semiconductor fiber fabrication and adding optoelectronic function to fibers are also discussed.
    Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2013; 01/2013
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    ABSTRACT: Flexible Si p-i-n junction fibers made by high pressure chemical vapor deposition offer new opportunities in textile photovoltaics and optoelectronics, as exemplified by their photovoltaic properties, gigahertz bandwidth for photodetection, and ability to waveguide light.
    Advanced Materials 12/2012; 25(10). · 15.41 Impact Factor
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    ABSTRACT: We experimentally demonstrate cross-phase modulation (XPM) on a subpicosecond timescale in a hydrogenated amorphous silicon-core, silica-clad optical fiber. Significant 10nm shifts in the probe wavelength are demonstrated through Kerr-induced refractive index changes.
    Information Optoelectronics, Nanofabrication and Testing; 11/2012
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    ABSTRACT: We present a silicon antiresonance reflecting optical (ARROW) fiber that has power dependent transmission properties. When the throughput power exceeds a nominal value the transmission bands close and the fiber can no longer transmit light.
    Information Optoelectronics, Nanofabrication and Testing; 11/2012
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    ABSTRACT: doi: 10.1146/annurev-matsci-073012-125958
    Annual Review of Materials Research 09/2012; · 15.63 Impact Factor
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    ABSTRACT: Laser annealing of an optical fiber with an amorphous silicon core is demonstrated. The annealing process produces a fiber that has a highly crystalline core, whilst reducing the optical transmission losses by ~3 orders of magnitude.
    06/2012;
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    ABSTRACT: The nonlinear transmission properties of hydrogenated amorphous silicon core fibers are characterized for short pulse propagation. The influence of the material quality and core size will be discussed in relation to device performance.
    06/2012;
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    ABSTRACT: We experimentally demonstrate cross-phase modulation (XPM) in a hydrogenated amorphous silicon-silica optical fiber. Additional numerical analysis shows that shifts in the probe wavelength are induced by the pump indicating potential for Kerr based switching applications.
    06/2012;
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    ABSTRACT: We explore the thermal nonlinearity in a-Si:H microcylindrical resonators fabricated from the silicon optical fiber platform. In particular, using a pump/probe technique, we determine the thermal response time and infer the material loss coefficient.
    05/2012;

Publication Stats

505 Citations
351.68 Total Impact Points

Institutions

  • 2005–2014
    • University of Southampton
      • Optoelectronics Research Centre (ORC)
      Southampton, England, United Kingdom
  • 2008–2012
    • Pennsylvania State University
      • Department of Chemistry
      University Park, MD, United States
    • Rutgers, The State University of New Jersey
      • Department of Materials Science and Engineering
      New Brunswick, NJ, United States