Integrated programmable spectral filter for frequency-multiplexed neuromorphic computers.

Artificial neural networks (ANN) are a groundbreaking technology massively employed in a plethora of fields. Currently, ANNs are mostly implemented through electronic digital computers, but analog photonic implementations are very interesting mainly because of low power consumption and high bandwidth. We recently demonstrated a photonic neuromorphic computing system based on frequency multiplexing that executes ANNs algorithms as reservoir computing and Extreme Learning Machines. Neuron signals are encoded in the amplitude of the lines of a frequency comb, and neuron interconnections are realized through frequency-domain interference. Here we present an integrated programmable spectral filter designed to manipulate the optical frequency comb in our frequency multiplexing neuromorphic computing platform. The programmable filter controls the attenuation of 16 independent wavelength channels with a 20 GHz spacing. We discuss the design and the results of the chip characterization, and we preliminary demonstrate, through a numerical simulation, that the produced chip is suitable for the envisioned neuromorphic computing application.

Integrated InP frequency discriminator for Phase-modulated microwave photonic links.

We report the design, fabrication and characterization of an integrated frequency discriminator on InP technology for microwave photonic phase modulated links. The optical chip is, to the best of our knowledge, the first reported in an active platform and the first to include the optical detectors. The discriminator, designed as a linear filter in intensity, features preliminary SFDR values the range between 67 and 79 dB.Hz(2/3) for signal frequencies in the range of 5-9 GHz limited, in principle, by the high value of the optical losses arising from the use of several free space coupling devices in our experimental setup. As discussed, these losses can be readily reduced by the use of integrated spot-size converters improving the SFDR by 17.3 dB (84-96 dB.Hz(2/3)). Further increase up to a range of (104-116 dB.Hz(2/3)) is possible by reducing the system noise eliminating the EDFA employed in the setup and using a commercially available laser source providing higher output power and lower relative intensity noise. Other paths for improvement requiring a filter redesign to be linear in the optical field are also discussed.

PAX7-FKHR fusion gene inhibits myogenic differentiation via NF-kappaB upregulation

OBJECTIVE: Alveolar rhabdomyosarcomas (ARMS) are characterised by a PAX3/7-FKHR translocation, which is presumed to promote a differentiation arrest in the myogenic lineage, in which setting secondary genetic events occur, resulting in sarcomagenesis. The aim of this study was to identify the mechanism by which PAX3/7-FKHR expression results in a myogenic differentiation block, as discrete from the secondary genetic events that complete the sarcomagenic process. METHODS: We performed a novel differential gene expression analysis comparing normal mesenchymal stem cells with previously generated non-tumorigenic mesenchymal stem cells expressing the PAX7-FKHR fusion gene, as well as with a known tumorigenic, PAX7-FKHR-expressing ARMS cell line, CW9019. RESULTS: This novel analysis uncovered the upregulation of the NF-kappaB pathway as a function of PAX3/7-FKHR expression, but distinct from the secondary sarcomagenic process; thus implicating NF-kappaB as a mediator of the PAX3/7-FKHR differentiation block. We further show that NF-kappaB activity is upregulated in PAX7-FKHR cells when compared to parental MSCs due to upregulation of the PI3K/AKT pathway. In addition we show that NF-kappaB inhibits myogenesis via activation of cyclinD1/ cdk4 complexes, which sequester MyoD1, a key myogenic transcription factor. CONCLUSIONS: Our results highlight the importance of the NF-kappaB pathway in myogenesis and sarcomagenesis and suggest that this pathway may be one of the potential therapeutic targets in the treatment of ARMS (AU)

All silicon waveguide spherical microcavity coupler device.

A coupler based on silicon spherical microcavities coupled to silicon waveguides for telecom wavelengths is presented. The light scattered by the microcavity is detected and analyzed as a function of the wavelength. The transmittance signal through the waveguide is strongly attenuated (up to 25 dB) at wavelengths corresponding to the Mie resonances of the microcavity. The coupling between the microcavity and the waveguide is experimentally demonstrated and theoretically modeled with the help of FDTD calculations.

Transmission and group-delay characterization of coupled resonator optical waveguides apodized through the longitudinal offset technique.

In this Letter, the amplitude and group delay characteristics of coupled resonator optical waveguides apodized through the longitudinal offset technique are presented. The devices have been fabricated in silicon-on-insulator technology employing deep ultraviolet lithography. The structures analyzed consisted of three racetracks resonators uniform (nonapodized) and apodized with the aforementioned technique, showing a delay of 5 ± 3 ps and 4 ± 0.5 ps over 1.6 and 1.4 nm bandwidths, respectively.

Apodized coupled resonator waveguides.

In this paper we propose analyse the apodisation or windowing of the coupling coefficients in the unit cells of coupled resonator waveguide devices (CROWs) as a means to reduce the level of secondary sidelobes in the bandpass characteristic of their transfer functions. This technique is regularly employed in the design of digital filters and has been applied as well in the design of other photonic devices such as corrugated waveguide filters and fiber Bragg gratings. The apodisation of both Type-I and Type-II structures is discussed for several windowing functions.