Photonic Crystal Nanocavities and Waveguides

Fabrication of optical structures has evolved to a precision which allows us to control light within etched nanostructures. Nano-optic cavities can be used for efficient and flexible concentration of light in small volumes, and control over both emission wavelength and frequency. Conversely, if a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light out of a semiconductor and to simultaneously enhance the spontaneous emission rate. Here we demonstrate the use of photonic crystals for efficient light localization and light extraction

Photonic Crystals and their Applications to Efficient Light Emitters

When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine and concentrate light into extremely small volumes and to obtain very high field intensities. Fabrication of optical structures has now evolved to a precision which allows us to control light within such etched nanostructures. Sub-wavelength nano-optic cavities can be used for efficient and flexible control over both emission wavelength and frequency, and nanofabricated optical waveguides can be used for efficient coupling of light between devices. The reduction of the size of optical components leads to their integration in large numbers and the possibility to combine different functionalities on a single chip. We show uses of such crystals in functional nonlinear optical devices, such as lasers, modulators, add/drop filters, polarizers and detectors

Effects of emotional valence on sense of agency require a predictive model

Sense of agency (SoA), a feeling that one's voluntary actions produce events in the external world, is a key factor behind every goal-directed human behaviour. Recent studies have demonstrated that SoA is reduced when one's voluntary action causes negative outcomes, compared to when it causes positive outcomes. It is yet unclear whether this emotional modulation of SoA is caused by predicting the outcome valence (prediction hypothesis) or by retrospectively interpreting the outcome (postdiction hypothesis). To address this, we emulated a social situation where one's voluntary action was followed by either another's negative emotional vocalisation or positive emotional vocalisation. Crucially, the relation between an action and the emotional valence of its outcome was predictable in some blocks of trials, but unpredictable in other blocks. Quantitative, implicit measures of SoA based on the intentional binding effect supported the prediction hypothesis. Our findings imply that the social-emotional modulation of SoA is based on predicting the emotional valence of action outcomes

Cavity QED with Multiple Hyperfine Levels

We calculate the weak-driving transmission of a linearly polarized cavity mode strongly coupled to the D2 transition of a single Cesium atom. Results are relevant to future experiments with microtoroid cavities, where the single-photon Rabi frequency g exceeds the excited-state hyperfine splittings, and photonic bandgap resonators, where g is greater than both the excited- and ground-state splitting.Comment: 6 pages, 10 figure

High aspect ratio silicon dioxide-coated single-walled carbon nanotube scanning probe nanoelectrodes

We have fabricated high aspect ratio, hydrophilic nanoelectrodes from individual single-walled carbon nanotubes (SWNTs) mounted on conductive atomic force microscope (AFM) tips for use as electrochemical probes. Individual SWNTs with an average diameter of 5 nm and up to 1.5 μm in length were passivated with nanometer-thick SiO_2 films, deposited conformally in an inductively coupled plasma reactor. The electrically insulating SiO_2 films improved the nanotube rigidity and stabilized the nanotube−AFM tip contact to enable use in aqueous environments. The nanotube tip was successfully exposed by subjecting the probe to nanosecond electrical pulse etching but only after electron beam irradiation in a transmission electron microscope (TEM). Probe functionality was verified by electrodepositing gold nanoparticles from aqueous solution only at the exposed tip

Magnetic skyrmions and skyrmion clusters in the helical phase of Cu2_2OSeO3_3

Skyrmions are nanometric spin whirls that can be stabilized in magnets lacking inversion symmetry. The properties of isolated skyrmions embedded in a ferromagnetic background have been intensively studied. We show that single skyrmions and clusters of skyrmions can also form in the helical phase and investigate theoretically their energetics and dynamics. The helical background provides natural one-dimensional channels along which a skyrmion can move rapidly. In contrast to skyrmions in ferromagnets, the skymion-skyrmion interaction has a strong attractive component and thus skyrmions tend to form clusters with characteristic shapes. These clusters are directly observed in transmission electron microscopy measurements in thin films of Cu$_2$OSeO$_3$. Topological quantization, high mobility and the confinement of skyrmions in channels provided by the helical background may be useful for future spintronics devices.Comment: 5 pages, 3 figures, 4 pages supplemen

Photonic Crystal Cavities and Waveguides

Recently, it has also become possible to microfabricate high reflectivity mirrors by creating two- and three-dimensional periodic structures. These periodic "photonic crystals" can be designed to open up frequency bands within which the propagation of electromagnetic waves is forbidden irrespective of the propagation direction in space and define photonic bandgaps. When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine and concentrate light into extremely small volumes and to obtain very high field intensities. Here we show the use of these "artificially" microfabricated crystals in functional nonlinear optical devices, such as lasers, modulators, and waveguides

Prediction of hearing recovery in sudden deafness treated with intratympanic steroids

The present study aims to obtain a probability model allowing the prediction of the auditory recovery in patients affected by sudden sensorineural hearing loss treated exclusively with intratympanic steroids. A monocentric retrospective chart review of three-hundred eighty-one patients has been performed. A Probit model was used to investigate the correlation between the success of the treatment (marked or total recovery according to Furuashi's criteria), and the delay between the onset of disease and the beginning of therapy. The age of the patients and the audiometric curve shapes were included in the analysis. Results show that delay is negatively correlated with the variable success. Considering the entire sample, each day of delay decreases by 3% the probability of success. The prediction model shows that for every day that passes from the onset of the disease the probability of success declines in absence of the medical treatment, hence we conclude that early treatment is strongly recommended

Surgical treatment of sporadic vestibular schwannoma in a series of 1006 patients. Trattamento chirurgico degli schwannomi vestibolari: risultati su una serie di 1006 pazienti

La gestione dello schwannoma vestibolare (SV) sporadico si è gradualmente evoluta negli ultimi decenni. Lo scopo di questo studio è di analizzare l’evoluzione negli esiti chirurgici dell’exeresi di queste lesioni, realizzata da un team neurotologico tra il 1990 e il 2006, attraverso differenti approcci. È stata eseguita una revisione retrospettica monocentrica dei dati clinici di 1006 pazienti. Al fine di valutare eventuali modifiche e progressi, il periodo di 17 anni è stato diviso in tre periodi, ciascuno comprendente rispettivamente 268 SV (1990- 1996), 299 SV (1997-2001), e 439 SV (2002-2006). Il follow-up medio è stato di 5,9 ± 2,4 anni. Complessivamente l’asportazione totale è stata ottenuta nel 99,4% dei casi. Il tasso di mortalità è stato dello 0,3%, la meningite e la perdita di liquido cefalo rachidiano (LCR) sono stati osservati nel 1,2% e il 9% dei casi, rispettivamente. La frequenza della perdita di LCR è diminuita dal 11,6% al 7,1% tra il primo e dell’ultimo periodo (p < 0,01) e la revisione chirurgica dal 3,4% al 0,9% (p < 0,05). Il nervo facciale è stato anatomicamente conservato nel 97,7% dei casi. Ad un anno, una buona funzione del nervo facciale è stata osservata nel 85,1% dei pazienti (I e II grado HouseBrackmann), con una variazione tra il primo e l’ultimo periodo che andava dal 78,4% al 87,6% (p < 0,05). Ad un anno post-operatorio la conservazione dell’udito è stata ottenuta nel 61,6% dei pazienti, passando dal 50,9% del primo periodo, al 69,0% del periodo piú recente (p < 0,05) (classe A + B + C dalla classificazione AAO-HNS). L’udito utile (classe A + B) è stato conservato nel 33,5% dei casi complessivamente, con percentuali comprese tra il 21,8% e 42% nel primo e nell’ultimo periodo rispettivamente (p < 0,01). Gli esiti chirurgici dell’asportazion dello schwannoma vestibolare sporadico sono migliorati negli anni per quanto riguarda i risultati funzionali del nervo facciale, la conservazione dell’udito, le perdite di liquido cefalorachidiano, principalmente grazie all’esperienza del team neurotologico. I risultati funzionali dopo la rimozione microchirurgica completa SV di grandi dimensioni dipendono dall’ esperienza maturata sulle lesioni di piccole dimensioniThe management of sporadic vestibular schwannoma (VS) has evolved in the last decades. The aim of this study was to analyse the evolution in surgical outcomes of VSs operated by a neurotological team between 1990 and 2006 by different approaches. A monocentric retrospective review of medical charts of 1006 patients was performed. In order to assess eventual changes and progress, the 17-years period was divided in three periods, each one comprehending 268 VS (1990-1996), 299 VS (1997-2001), and 439 VS (2002-2006). Mean follow-up was 5.9 ± 2.4 years. Overall, complete VS removal was achieved in 99.4% of cases. Mortality rate was 0.3%, meningitis and CSF leaks were observed in 1.2 % and 9 % of the cases, respectively. CSF leakage decreased from 11.6% to 7.1% between the first and last period (p < 0.01) as well as revision surgery from 3.4 % to 0.9 % (p < 0.05). Facial nerve was anatomically preserved in 97.7% of cases. At one year, a good facial nerve function was observed in 85.1% of patients (grade I and II of House-Brackmann grading scale), which ranged between the first and last period from 78.4% to 87.6% (p <0.05). At one year, hearing preservation was obtained in 61.6% of patients, which increased from the first period to the last one from 50.9% to 69.0% (p < 0.05) (class A+B+C from the AAO-HNS classification). Useful hearing (class A+B) was observed in 33.5% of cases overall, with 21.8% and 42% in the first and last period, respectively (p < 0.01). Surgical outcomes of sporadic vestibular schwannoma have improved concerning facial nerve function outcomes, hearing preservation and cerebrospinal fluid (CSF) leaks, mainly due to the neuro-otological team's experience. Functional results after complete microsurgical removal of large VS depend on experience gained on small VS removal