Record Purcell factors in ultracompact hybrid plasmonic ring resonators

For integrated optical devices and traveling-wave resonators, realistic use of the superior wave-matter interaction offered by plasmonics is impeded by ohmic loss, which increases rapidly with mode volume reduction. In this work, we report composite hybrid plasmonic waveguides (CHPWs) that are not only capable of guiding subwavelength optical mode with long-range propagation but also unrestricted by stringent requirements in structural, material, or modal symmetry. In these asymmetric CHPWs, the versatility afforded by coupling dissimilar plasmonic modes provides improved fabrication tolerance and more degrees of device design optimization. Experimental realization of CHPWs demonstrates propagation loss and mode area of 0.03 dB/μm and 0.002 μm2, corresponding to the smallest combination among long-range plasmonic structures reported to date. CHPW ring resonators with 2.5-μm radius were realized with record Purcell factor compared with existing plasmonic and dielectric resonators of similar radii.

Generation of polarization-entangled photon pairs in a Bragg reflection waveguide

We demonstrate experimentally that spontaneous parametric down-conversion in an AlxGa(1-x)As semiconductor Bragg reflection waveguide can make for paired photons highly entangled in the polarization degree of freedom at the telecommunication wavelength of 1550 nm. The pairs of photons show visibility higher than 90% in several polarization bases and violate a Clauser-Horne-Shimony-Holt Bell-like inequality by more than 3 standard deviations. This represents a significant step toward the realization of efficient and versatile self pumped sources of entangled photon pairs on-chip.

Monolithic source of photon pairs

The creation of monolithically integratable sources of single and entangled photons is a top research priority with formidable challenges: The production, manipulation, and measurement of the photons should all occur in the same material platform, thereby fostering stability and scalability. Here we demonstrate efficient photon pair production in a semiconductor platform, gallium arsenide. Our results show type-I spontaneous parametric down-conversion of laser light from a 2.2 mm long Bragg-reflection waveguide, and we estimate its internal pair production efficiency to be 2.0×10(-8) (pairs/pump photon). This is the first time that significant pair production has been demonstrated in a structure that can be electrically self-pumped and which can form the basis for passive optical circuitry, bringing us markedly closer to complete integration of quantum optical technologies.

Proposal for on-chip generation and control of photon hyperentanglement

An on-chip waveguide-based source of entangled photons capable of switching between generating time-energy entangled and hyperentangled (entangled in both time energy and polarization) photon pairs is proposed. The switching can be done all-optically by rotating the pump polarization. The source is based on multichannel phase matching in Bragg reflection waveguides achieved by engineering the Fresnel reflection of photonic bandgap claddings for differently polarized modes. Analytical results are confirmed in fully vectorial numerical simulations.

Phase matching in monolithic Bragg reflection waveguides

We report what is believed to be the first observation of second-harmonic generation by type I phase matching the bulk chi(xyz)((2))(d(14)) nonlinear coefficient using Bragg reflection waveguides. Second-harmonic power of 0.7 microW was observed for a pump wavelength of 1587.8 nm with an average power of 25.2 mW and a pulse width of approximately 2 ps at a repetition rate of 75.6 MHz. An order of magnitude enhancement between the phase-matched and un-phase-matched second-harmonic conversion efficiency has been observed. Conversion efficiency at the phase-matched wavelengths was 0.001%. The bandwidth of the second harmonic was found to be equal to 0.43 nm, agreeing with the theoretical predictions.

Dispersion tailoring of the quarter-wave Bragg reflection waveguide

We present analytical formulae for the polarization dependent first- and second-order dispersion of a quarter-wave Bragg reflection waveguide (QtW-BRW). Using these formulae, we develop several qualitative properties of the QtW-BRW. In particular, we show that the birefringence of these waveguides changes sign at the QtW wavelength. Regimes of total dispersion corresponding to predominantly material-dominated and waveguide-dominated dispersion are identified. Using this concept, it is shown that the QtW-BRW can be designed so as to provide anomalous group velocity dispersion of large magnitude, or very small GVD of either sign, simply by an appropriate chose of layer thicknesses. Implications on nonlinear optical devices in compound semiconductors are discussed.

Phase matching using Bragg reflection waveguides for monolithic nonlinear optics applications

A novel design to achieve phase matching between modes of a vertical distributed Bragg reflector waveguide and those of a conventional total internal reflection waveguide is reported for the first time. The device design and structure lend themselves to monolithic integration with active devices using well developed photonic fabrication technologies. Due to the lack of any modulation of the optical properties in the direction of propagation, the device promises very low insertion loss. This property together with the large overlap integral between the interacting fields dramatically enhances the conversion efficiency. The phase matching bandwidth, tunability and dimensions of these structures make them excellent contenders to harness optical nonlinearities in compact, low insertion loss monolithically integrable devices.

Life-threatening cervical necrotizing fasciitis

Eight cases of cervical necrotizing fasciitis are presented. Three were odontogenic, two were pharyngeal in origin and three were primary or idiopathic. Soft tissue gas was recognized in four patients. The bacteriology showed streptococci on the top of the list (50%), while for the idiopathic cases, it was monomicrobial and caused by staphylococci. Third generation cephalosporin and metronidazole represent good initial empirical antibacterial coverage. Histopathologically, all cases showed extensive necrosis of the debrided fascia and vascular thrombosis of the dermal vessels. The mortality rate was 3/8 (37.5%). Early diagnosis of cervical necrotizing fasciitis and initiation of definitive therapy in an intensive care environment is essential to minimize mortality. It is also important to recognize that this devastating infection may occur spontaneously, and it should be suspected in patients with unexplained soft tissue pain and tenderness.

Poor prognosis and limited therapeutic options in patients with Budd-Chiari syndrome and portal venous system thrombosis

OBJECTIVES

Therapeutic options in Budd-Chiari syndrome (BCS) are highly dependent on the site and extent of hepatic vein thrombosis. The aim of this study was to evaluate the effect of additional portal venous system thrombosis on the clinical presentation, treatment and outcome in patients with BCS.

PATIENTS

Clinical notes of 51 patients with BCS admitted to our centre were evaluated. We identified 13 patients (25%) with BCS and additional portal venous system thrombosis. Ten patients were female and three male with a mean age at presentation of 42 years (range 32-67).

RESULTS

An underlying haematological aetiology was identified in 10 of the 13 patients. Only four patients (31%) were anticoagulated before referral to our centre. In addition to hepatic vein thrombosis seven patients had portal vein thrombosis (PVT), three had PVT, splenic vein (SV) and superior mesenteric vein (SMV) thrombosis and three had either SV, SMV or inferior vean cava (IVC) thrombosis. The presentation was acute in three patients, subacute in six and chronic in four with a high incidence of encephalopathy (6/13; 46%). Treatment included liver transplantation (four), mesoatrial shunt (one) and balloon dilatation of hepatic veins (two). Six patients were treated medically as all other options were considered too risky or technically impossible. Nine of 13 patients (70%) died either after surgery or before any treatment could be instituted (median survival 1 month), compared to 14/38 (37%) in patients with isolated hepatic vein thrombosis (median survival 6.3 years).

CONCLUSION

We conclude that patients with BCS and portal venous system thrombosis constitute a unique group with limited therapeutic options and poor prognosis. The importance of early recognition and anticoagulation of patients with BCS is emphasized.