3,213 research outputs found

    Polarization effects in microcoil resonators

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    Optical microcoil resonators (OMRs), formed by coiling a micron-diameter fibre around a rod as shown in Figure 1a, provide a unique resonator geometry in which light can evanescently couple between adjacent turns to produce high Q resonances. Furthermore, OMRs fabricated from a pigtailed fibre taper offer much lower coupling losses than cavity resonators. Applications in fields such as fluidic and temperature sensing have already been investigated, and the small fibre diameter and effective modal area indicate that OMRs are a promising platform for studying nonlinear interactions. A detailed understanding of OMR optical characteristics is crucial for further development, but theoretical studies have thus far neglected any polarization dependency. In this work, the influence of the fibre’s birefringence on the polarization of propagating light was studied by numerically solving polarization dependant coupled mode equations. The resulting transmission and dispersion properties are discussed for different degrees of fibre twist (Figure 1b). In addition to the linear behaviour, the nonlinear regime was explored, by incorporating a Kerr term, and found to be strongly enhanced around resonances

    Magneto-optical Kerr effect in Eu1xCaxB6Eu_{1-x}Ca_{x}B_{6}

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    We have measured the magneto-optical Kerr rotation of ferromagnetic Eu1xCaxB6Eu_{1-x}Ca_{x}B_{6} with x=0.2 and 0.4, as well as of YbB6YbB_{6} serving as the non-magnetic reference material. As previously for EuB6EuB_{6}, we could identify a feature at 1 eVeV in the Kerr response which is related with electronic transitions involving the localized 4f electron states. The absence of this feature in the data for YbB6YbB_{6} confirms the relevance of the partially occupied 4f states in shaping the magneto-optical features of EuEu-based hexaborides. Disorder by CaCa-doping broadens the itinerant charge carrier contribution to the magneto-optical spectra

    Observation of soliton explosions in a passively mode-locked fiber laser

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    Soliton explosions are among the most exotic dissipative phenomena studied in mode-locked lasers. In this regime, a dissipative soliton circulating in the laser cavity experiences an abrupt structural collapse, but within a few roundtrips returns to its original quasi-stable state. In this work we report on the first observation of such events in a fiber laser. Specifically, we identify clear explosion signatures in measurements of shot-to-shot spectra of an Yb-doped mode-locked fiber laser that is operating in a transition regime between stable and noise-like emission. The comparatively long, all-normal-dispersion cavity used in our experiments also permits direct time-domain measurements, and we show that the explosions manifest themselves as abrupt temporal shifts in the output pulse train. Our experimental results are in good agreement with realistic numerical simulations based on an iterative cavity map.Comment: 5 pages, 5 figures, submitte

    Alien Registration- Broderick, Ellen G. (Portland, Cumberland County)

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    https://digitalmaine.com/alien_docs/24702/thumbnail.jp

    Alien Registration- Broderick, Ellen G. (Portland, Cumberland County)

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    https://digitalmaine.com/alien_docs/24702/thumbnail.jp

    Alien Registration- Broderick, Ellen G. (Portland, Cumberland County)

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    https://digitalmaine.com/alien_docs/24702/thumbnail.jp

    Novel applications of fibre tapers

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    In this talk we will discuss new applications for fibre tapers ranging from femtosecond pulse manipulation to optical clock generation in micro-coil resonators. Fundamental to these interactions is the enhanced nonlinearity arising from the smaller cores making compact optical devices possible

    Theory and design of Inx_{x}Ga1x_{1-x}As1y_{1-y}Biy_{y} mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 μ\mum on InP substrates

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    We present a theoretical analysis and optimisation of the properties and performance of mid-infrared semiconductor lasers based on the dilute bismide alloy Inx_{x}Ga1x_{1-x}As1y_{1-y}Biy_{y}, grown on conventional (001) InP substrates. The ability to independently vary the epitaxial strain and emission wavelength in this quaternary alloy provides significant scope for band structure engineering. Our calculations demonstrate that structures based on compressively strained Inx_{x}Ga1x_{1-x}As1y_{1-y}Biy_{y} quantum wells (QWs) can readily achieve emission wavelengths in the 3 -- 5 μ\mum range, and that these QWs have large type-I band offsets. As such, these structures have the potential to overcome a number of limitations commonly associated with this application-rich but technologically challenging wavelength range. By considering structures having (i) fixed QW thickness and variable strain, and (ii) fixed strain and variable QW thickness, we quantify key trends in the properties and performance as functions of the alloy composition, structural properties, and emission wavelength, and on this basis identify routes towards the realisation of optimised devices for practical applications. Our analysis suggests that simple laser structures -- incorporating Inx_{x}Ga1x_{1-x}As1y_{1-y}Biy_{y} QWs and unstrained ternary In0.53_{0.53}Ga0.47_{0.47}As barriers -- which are compatible with established epitaxial growth, provide a route to realising InP-based mid-infrared diode lasers.Comment: Submitted versio

    Nonlinear optics of fibre event horizons

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    The nonlinear interaction of light in an optical fibre can mimic the physics at an event horizon. This analogue arises when a weak probe wave is unable to pass through an intense soliton, despite propagating at a different velocity. To date, these dynamics have been described in the time domain in terms of a soliton-induced refractive index barrier that modifies the velocity of the probe. Here, we complete the physical description of fibre-optic event horizons by presenting a full frequency-domain description in terms of cascaded four-wave mixing between discrete single-frequency fields, and experimentally demonstrate signature frequency shifts using continuous wave lasers. Our description is confirmed by the remarkable agreement with experiments performed in the continuum limit, reached using ultrafast lasers. We anticipate that clarifying the description of fibre event horizons will significantly impact on the description of horizon dynamics and soliton interactions in photonics and other systems.Comment: 7 pages, 5 figure
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