High-responsivity graphene photodetectors integrated on silicon microring resonators

Abstract: Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs’ low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10−9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print

L’acquisizione dei profili intonativi di italiano L2 attraverso un’unità di apprendimento in modalità blended learning

This study assumes that adopting specific teaching techniques can improve learners’ recognition and production of the prosodic features of Italian L2, with special reference to some particular intonation contours. In fact, according to this assumption, which is supported in the literature also by neurological motivations, adult learners are not subject to evolution in the suprasegmental features that contribute to the characterization of the so called “foreign accent”. In this study, we analyse the effectiveness of training in the production and perception of some intonational patterns: polar questions and exclamatives. The intonational analysis is supported and integrated by an auditory evaluation on the adequacy of intonation patterns produced by different learners in different experimental phases

High responsivity near-infrared photodetectors in evaporated Ge-on-Si

Germanium is considered the most suitable semiconductor for monolithic integration of near-infrared detectors on silicon photonic chips. Here we report on Ge-on-Si near-infrared photodetectors fabricated by thermal evaporation, demonstrating the use of phosphorus spin-on-dopant to compensate the acceptor states introduced by dislocations. The detectors exhibit 1.55 mu m responsivities as high as 0.1 A/W, more than two orders of magnitude larger than in undoped devices and comparing well with state-of-the-art p-i-n photodiodes. This approach enables simple and low-cost monolithic integration of near-infrared sensors with silicon photonics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747213

Fast and Broadband SOI Photonic Integrated Microwave Phase Shifter

An integrated silicon-on-insulator microwave photonic phase shifter based on an optical deinterleaver and a reverse-biased pn-junction waveguide providing broadband phase shift up to more than 400° with fast reconfiguration time of 1 ns is demonstrated

Photonic integrated microwave phase shifter up to the mm-wave band with fast response time in silicon-on-insulator technology

An integrated silicon-on-insulator microwave photonic phase shifter is demonstrated, based on an optical deinterleaver providing box-like transfer function and a reverse-biased pn-junction waveguide optical phase shifter. The photonic integrated circuit is proved to precisely control the phase of microwave signals in a range of more than 400° with a fast reconfiguration time of 1 ns, with a broad bandwidth of more than 6 GHz around an RF carrier flexibly selectable between 10 and 16 GHz, and limited in-band RF power variations. Moreover, thanks to the periodic behavior of the deinterleaver, the device is demonstrated to correctly control the phase of signals in the mm-wave band (>30 GHz) as well. The performance guaranteed by the proposed microwave phase shifter suggests its use in demanding applications as rapidly reconfiguring phased array antennas in future wireless communications systems