Atenuasi ultrasonik dan modulus ricih pada suhu genting superkonduktor terdop sederhana (Tl0.8Bi0.2)Sr2 (Ca0.9Cr0.1)Cu2 O7

Modulus ricih dan atenuasi ultrasonik superkonduktor suhu tinggi terdop sederhana (Tl0.8Bi0.2)Sr2 (Ca0.9Cr0.1)Cu2 O7 (Tl-1212) dengan suhu genting (Tc ) 98 K telah dikaji. Modulus ricih, G meningkat apabila suhu diturunkan daripada 240 K ke 80 K yang menunjukkan pengerasan kekisi. Walau bagaimanapun, pada suhu antara 160 K hingga 190 K modulus ricih menunjukkan anomali menandakan kecenderungan untuk kekisi melembut. Berhampiran suhu genting modulus ricih menunjukkan pelembutan kekisi iaitu ketakselanjaran pada cerun (dG/dT) dan ini sejajar dengan ciri peralihan fasa termodinamik tertib ke dua. Peratus perubahan modulus ricih antara 240 K dan 80 K ialah 5.5%. Atenuasi ultrasonik menunjukkan penurunan mendadak daripada 240 K ke 210 K diikuti dengan profil yang hampir mendatar sehingga 140 K. Puncak atenuasi dicerap berhampiran suhu genting dan ini menunjukkan penyerapan tenaga akustik meningkat apabila bahan memasuki fasa mensuperkonduksi. Anomali modulus ricih dan atenuasi ultrasonik ini dijelaskan melalui peralihan fasa tertib kedua dan tertiban oksigen jarak dekat dalam satah Cu-O unit sel bahan superkonduktor ini

Establishment of Wolbachia strain wAlbB in Malaysian populations of Aedes aegypti for dengue control

Dengue has enormous health impacts globally. A novel approach to decrease dengue incidence involves the introduction of Wolbachia endosymbionts that block dengue virus transmission into populations of the primary vector mosquito, Aedes aegypti. The wMel Wolbachia strain has previously been trialed in open releases of Ae. aegypti; however, the wAlbB strain has been shown to maintain higher density than wMel at high larval rearing temperatures. Releases of Ae. aegypti mosquitoes carrying wAlbB were carried out in 6 diverse sites in greater Kuala Lumpur, Malaysia, with high endemic dengue transmission. The strain was successfully established and maintained at very high population frequency at some sites or persisted with additional releases following fluctuations at other sites. Based on passive case monitoring, reduced human dengue incidence was observed in the release sites when compared to control sites. The wAlbB strain of Wolbachia provides a promising option as a tool for dengue control, particularly in very hot climates

Multiwavelength L-band fiber laser with bismuth-oxide EDF and photonic crystal fiber.

A multiwavelength laser comb using a bismuth-based erbium-doped fiber and 50 m photonic crystal fiber is demonstrated in a ring cavity configuration. The fiber laser is solely pumped by a single 1455 nm Raman pump laser to exploit its higher power delivery compared to that of a single-mode laser diode pump. At 264 mW Raman pump power and 1 mW Brillouin pump power, 38 output channels in the L-band have been realized with an optical signal-to-noise ratio above 15 dB and a Stokes line spacing of 0.08 nm. The laser exhibits a tuning range of 12 nm and produces stable Stokes lines across the tuning range between Brillouin pump wavelengths of 1603 nm and 1615 nm

Polarisation effects in optical microresonators

Polarization effects in different types of optical microresonators are studied in detail. It is observed that microresonators with tighter axial power confinement, such as MBRs and micro-milled resonators, show larger cross-polarization coupling efficiencies

Microtaper fiber excitation effects in bottle microresonators

We have carried out a systematic study of the effect of microtaper diameter on the spectral characteristics of bottle microresonators. By increasing the microtaper-diameter (Dt) from 2µm to 10µm results in progressively cleaner spectra. The transmission depth at resonance varies from ~15dB (@Dt = 2µm) to >3dB (@Dt = 10µm). The loaded Q factors were measured to be >10+6 in all cases. However, with microtaper Dt = 10µm clearly-resolved single resonance peaks could be observed and free-spectral ranges could be easily identified. At some transmission resonances, we have observed LP01 to LP11 mode transformation at the excitation microtaper waist, for the first time, as the resonance is scanned

Microgrooved bottle microresonators

Spectral cleaning in bottle microresonators is presented by inscribing periodic surface microgrooves. Cleaning down to single strong WGM family is demonstrated, with Qs > 105 (similar to original microresonator)

High-Q plasmonic bottle microresonators

Surface Plasmon Waves (SPWs) supported by thin metal films have been used to implement high performance surface sensitive devices, such as refractometric and biochemical sensors. Recently all-glass bottle microresonators (BMRs), supporting whispering-gallery modes (WGM), have been studied in-depth with the intention to be used in advanced photonic applications, such as CQED, nonlinear devices and miniaturized sensors. In this work, we combine the two structures and demonstrate the first hybrid plasmonic BMR (PBMR). A gold layer has been deposited on the top surface of a glass BMR, fabricated by the “soften-and-compress” technique. We developed a polarization-resolving measurement set-up to fully characterize fabricated PBMRs. The uncoated BMR had 181µm waist diameter, 125µm stem diameter and 400µm length. Due to the surface curvature the gold film covered only the top BMR half with a characteristic meniscus shape with maximum thickness of 30nm. The meniscus provides appropriately tapered edges, which facilitate the adiabatic transformation of BMR WGMs into SPW and vice-versa. This results in low transition losses, which combined with partially-metal-coated resonator, can result in high hybrid-PBMR Qs.The transmission spectra of the hybrid PBMR are dramatically different to the original uncoated BMR. Under TE(TM) excitation, the PBMR showed composite resonances with Q of ~2100(850) and almost identical ~3nm FSR. We have accurately fitted the observed transmission resonances with Lorentzian-shape curves and showed that the TE/TM composite resonances comprise two/three partially overlapping resonances with Qs in excess of 2900 and 2500, respectively. These are the highest Qs observed in plasmonic microcavities

Optical microstub resonator lasers

We describe the fabrication and optical performance of a new passive and active optical microstub resonator (MSR). The technique is extremely simple and enables the fabrication of high quality resonators. They are primarily cylindrical cavities (“stubs”) 10's of microns long spliced to two fiber stems of smaller diameter on either side. The splicing makes the edges of the “stub” rounded and smooth, improving the optical performance. The fabricated MSRs had typical stem/cavity diameters of 125µm/200µm, respectively, and 50-200µm lengths. Strong resonances with coupling efficiencies and Q factors > 15dB and 106, respectively, were demonstrated.Using a special Ytterbium doped fiber with doped core diameter of 220µm and cladding diameter of 240µm, we formed active MSRs with 50-500µm lengths and 125µm stem diameters. The active MSRs were side pumped by 980nm single-mode diodes through their stems. Residual pump and generated signal were monitored at the opposite fiber stem end. Strong lasing peaks in the 1060nm wavelength range were observed. No transversely scattered signal/pump light was detected. This indicates that the whispering-gallery modes were formed at the inner doped core/cladding interface. In stark contrast with previous microlaser demonstrations, this laser does not need additional microtapers/waveguides for launching or collecting light. This is the first demonstration of a robust, fully integrated, stand-alone microresonator laser where pump launching and signal collection is achieved by the fiber stems, used to form the microcavity. This is a major advancement and will impact significantly the development of future advanced sensor applications