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We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 µm) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ∼12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary.

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We report a new phenomenon related to Al-induced carrier confinement at the interface in core-shell GaAs/Al(x)Ga(1-x)As nanowires grown using metal-organic vapor phase epitaxy with Au as catalyst. All Al(x)Ga(1-x)As shells strongly passivated the GaAs nanowires, but surprisingly the peak photoluminescence (PL) position and the intensity from the core were found to be a strong function of Al composition in the shell at low temperatures. Large and systematic red shifts of up to ~66 nm and broadening in the PL emission from the GaAs core were observed when the Al composition in the shell exceeded 3%. On the contrary, the phenomenon was observed to be considerably weaker at the room temperature. Cross-sectional transmission electron microscopy reveals Al segregation in the shell along six Al-rich radial bands displaying a 3-fold symmetry. Time-resolved PL measurements suggest the presence of indirect electron-hole transitions at the interface at higher Al composition. We discuss all possibilities including a simple shell-core-shell model using simulations where the density of interface traps increases with the Al content, thus creating a strong local electron confinement. The carrier confinement at the interface is most likely related to Al inhomogeneity and/or Al-induced traps. Our results suggest that a low Al composition in the shell is desirable in order to achieve ideal passivation in GaAs nanowires.

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ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 µW cm(-2) at a wavelength of 365 nm and response time of 0.9 s.

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Saturated Collision Amplifier (SCA) is a novel amplification scheme that uses SOA saturation in order to maximize the output power and minimize the ASE noise and the polarization sensitivity. We demonstrate the SCA reach extension in a commercial single-wavelength XGPON1 prototype system where bidirectional optical budget of up to 50 dB is obtained. The traffic performances are compared between the SCA and the conventional SOA extender. The novel extension scheme is demonstrated also for two- and four-wavelength 10 Gbit/s unidirectional downstream configurations with 45 km and 100 km transmission distances with 58-dB maximum total optical budget for each wavelength.

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Pyrene mediated noncovalent attachment of a chlorophyll derivative, pyro-pheophorbide a, to a soluble single wall carbon nanotube is reported and the resultant CD, UV-Vis absorbance, fluorescence and 1H NMR spectra are discussed.

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Transformation of self-assembled InAs quantum dots (QDs) on InP(100) into quantum rings (QRs) is studied. In contrast to the typical approach to III--V semiconductor QR growth, the QDs are not capped to form rings. Atomic force micrographs reveal a drastic change from InAs QDs into rings after a growth interruption in tertiarybutylphosphine ambient. Strain energy relief in the InAs QD is discussed and a mechanism for dot-to-ring transformation by As/P exchange reactions is proposed.

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We present a robust method for computing the reflection of arbitrarily shaped and sized beams from finite thickness photonic crystals. The method is based on dividing the incident beam into plane waves, each of which can be solved individually using Bloch periodic boundary conditions. This procedure allows us to take a full advantage of the crystal symmetry and also leads to a linear scaling of the computation time with respect to the number of plane waves needed to expand the incident beam. The algorithm for computing the reflection of an individual plane wave is also reviewed. Finally, we find an excellent agreement between the computational results and measurement data obtained from opals that are synthesized using polystyrene and poly(methyl methacrylate) microspheres.