Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator.

Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena. Compared to amorphous materials, crystalline structures often exhibit desirable properties such as high indices of refraction, high nonlinearities, and large windows of transparency, making them ideal for use in frequency comb generation, microlasing and all-optical processing. In particular, crystalline materials can also possess a non-centrosymmetric structure which gives rise to the second order nonlinearity, necessary for three photon processes such as frequency doubling and parametric down-conversion. Here we report a novel route to fabricating crystalline zinc selenide microcylindrical resonators from our semiconductor fibre platform and demonstrate their use for tunable, low power continuous wave second harmonic generation. Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator. By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500-22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

Nonlinear transmission properties of hydrogenated amorphous silicon core fibers towards the mid-infrared regime.

The nonlinear transmission properties of hydrogenated amorphous silicon (a-Si:H) core fibers are characterized from the near-infrared up to the edge of the mid-infrared regime. The results show that this material exhibits linear losses on the order of a few dB/cm, or less, over the entire wavelength range, decreasing down to a value of 0.29 dB/cm at 2.7µm, and negligible nonlinear losses beyond the two-photon absorption (TPA) edge ~ 1.7µm. By measuring the dispersion of the nonlinear Kerr and TPA parameters we have found that the nonlinear figure of merit (FOM(NL)) increases dramatically over this region, with FOM(NL) > 20 around 2µm and above. This characterization demonstrates the potential for a-Si:H fibers and waveguides to find use in nonlinear applications extending beyond telecoms and into the mid-infrared regime.

Array of tapered semiconductor waveguides in a fiber for infrared image transfer and magnification.

The proof-of-concept of an infrared imaging tip by an array of infrared waveguides tapered as small as 2 µm is demonstrated. The fabrication is based on a high-pressure chemical fluid deposition technique to deposit precisely defined periodic arrays of Ge and Si waveguides within a microstructured optical fiber template made of silica to demonstrate the proposed concept at wavelengths of 10.64 µm and 1.55 µm, respectively. The essential features of the imaging system such as isolation between adjacent pixels, magnification, optical throughput, and image transfer characteristics are investigated. Near-field scanning at 3.39 µm wavelength using a single tapered Ge core is also demonstrated.

All-optical modulation using two-photon absorption in silicon core optical fibers.

All-optical modulation based on degenerate and non-degenerate two-photon absorption (TPA) is demonstrated within a hydrogenated amorphous silicon core optical fiber. The nonlinear absorption strength is determined by comparing the results of pump-probe experiments with numerical simulations of the coupled propagation equations. Subpicosecond modulation is achieved with an extinction ratio of more than 4 dB at telecommunications wavelengths, indicating the potential for these fibers to find use in high speed signal processing applications.

High index contrast semiconductor ARROW and hybrid ARROW fibers.

We investigate the guidance properties of two photonic crystal fibers that have been fabricated by filling the holes of a silica template with hydrogenated amorphous silicon inclusions. The first is an all-solid fiber that guides light via an antiresonant reflecting optical waveguiding mechanism and the second is only partially filled so that it guides light by a hybrid of modified total internal reflection and antiresonant reflecting optical waveguiding. It will be shown that, by selectively filling the silica template to leave an unfilled internal ring of holes, the fiber's confinement loss can be reduced significantly. This novel fiber design in which the light guided in the silica core can be modified by the semiconductor cladding provides a route to integrating functional semiconductor fibers with existing silica fiber infrastructures.

Tapered silicon optical fibers.

The tapering of silicon optical fibers is demonstrated using a fusion splicer. The silicon fibers are fabricated using a high pressure chemical deposition technique to deposit an amorphous silicon core inside a silica capillary and the tapering is performed in a separate post-process. Optical and material characterization has revealed a smooth transition region leading to a uniform tapered waist that are both simultaneously crystallized to yield a solid polysilicon core. The strong mode confinement and low taper loss measured in the silicon fibers verifies this tapering approach for the fabrication of structures with nanoscale core dimensions.

Large mode area silicon microstructured fiber with robust dual mode guidance.

A silicon microstructured fiber has been designed and fabricated using a pure silica photonic bandgap guiding fiber as a 3D template for materials deposition. The resulting silicon fiber has a micron sized core but with a small core-cladding index contrast so that it only supports two guided modes. It will be shown that by using the microstructured template this fiber exhibits a number of similar guiding properties to the more traditional index guiding air-silica structures. The large mode areas and low optical losses measured for the silicon microstructured fiber demonstrate its potential to be integrated with existing fiber infrastructures.

Endogenous group B streptococcal endophthalmitis in a preterm infant.

Endogenous endophthalmitis is a rare complication of bacteremia. Proper intervention is critical, as the majority of affected patients lose vision in the infected eye. Treatment options include systemic antibiotics, intravitreous antibiotics and vitrectomy. We report a case of endogenous endophthalmitis presenting as leukocoria in a premature neonate with group B streptococcal meningitis.

An age old debate.

On the national level, only Oregon currently permits assisted suicide. Thirty-five states have statutes that ban the practice while nine others (including Michigan) seemingly prohibit it under common law principles, without a specific statute that speaks to the point.

Amyloidoma of the gasserian ganglion.

A case report, the third in the literature, is presented of a patient whose progressive numbness in the second and third divisions of the trigeminal nerve led to the discovery of an isolated amyloidoma of the gasserian ganglion. The clinical impression of tumor was confirmed by surgical and pathologic findings.