114 research outputs found
Guided-wave photodetectors in germanium on optical chips in silicon-on-insulator
We report the integration of near-infrared waveguide photodetectors in polycrystalline Germanium with Silicon on Insulator optical chips for power monitor applications. We discuss design and fabrication of the devices as well as their characterization in terms of dark current, responsivity and signal to noise ratio
High-speed double layer graphene electro-absorption modulator on SOI waveguide
We report on a C-band double layer graphene electro-absorption modulator on a passive SOI platform showing 29GHz 3dB-bandwith and NRZ eye-diagrams extinction ratios ranging from 1.7 dB at 10 Gb/s to 1.3 dB at 50 Gb/s. Such high modulation speed is achieved thanks to the quality of the CVD pre-patterned single crystal growth and transfer on wafer method that permitted the integration of high-quality scalable graphene and low contact resistance. By demonstrating this high-speed CVD graphene EAM modulator integrated on Si photonics and the scalable approach, we are confident that graphene can satisfy the main requirements to be a competitive technology for photonics
Chirp management in silicon-graphene electro absorption modulators
We study the frequency chirp properties of graphene-on-silicon electro-absorption modulators (EAMs). By experimentally measuring the chirp of a 100 \ub5m long single layer graphene EAM, we show that the optoelectronic properties of graphene induce a large positive linear chirp on the optical signal generated by the modulator, giving rise to a maximum shift of the instantaneous frequency up to 1.8 GHz. We exploit this peculiar feature for chromatic-dispersion compensation in fiber optic transmission thanks to the pulse temporal lensing effect. In particular, we show dispersion compensation in a 10Gb/s transmission experiment on standard single mode fiber with temporal focusing distance (0-dB optical-signal-to-noise ratio penalty) of 60 km, and also demonstrate 100 km transmission with a bit error rate largely lower than the conventional Reed-Solomon forward error correction threshold of 10 123
Photo Thermal Effect Graphene Detector Featuring 105 Gbit s-1 NRZ and 120 Gbit s-1 PAM4 Direct Detection
The challenge of next generation datacom and telecom communication is to
increase the available bandwidth while reducing the size, cost and power
consumption of photonic integrated circuits. Silicon (Si) photonics has emerged
as a viable solution to reach these objectives. Graphene, a single-atom thick
layer of carbon5, has been recently proposed to be integrated with Si photonics
because of its very high mobility, fast carrier dynamics and ultra-broadband
optical properties. Here, we focus on graphene photodetectors for high speed
datacom and telecom applications. High speed graphene photodetectors have been
demonstrated so far, however the most are based on the photo-bolometric (PB) or
photo-conductive (PC) effect. These devices are characterized by large dark
current, in the order of milli-Amperes , which is an impairment in
photo-receivers design, Photo-thermo-electric (PTE) effect has been identified
as an alternative phenomenon for light detection. The main advantages of
PTE-based photodetectors are the optical power to voltage conversion, zero-bias
operation and ultra-fast response. Graphene PTE-based photodetectors have been
reported in literature, however high-speed optical signal detection has not
been shown. Here, we report on an optimized graphene PTE-based photodetector
with flat frequency response up to 65 GHz. Thanks to the optimized design we
demonstrate a system test leading to direct detection of 105 Gbit s-1
non-return to zero (NRZ) and 120 Gbit s-1 4-level pulse amplitude modulation
(PAM) optical signal
Complex effective index in graphene-silicon waveguides
We report for the first time and characterize experimentally the complex optical
conductivity of graphene on silicon photonic waveguides. This permits us to predict
accurately the behavior of photonic integrated devices encompassing graphene layers.
Exploiting a Si microring add/drop resonator, we show the effect of electrical gating of
graphene on the complex effective index of the waveguide by measuring both the wavelength
shift of the resonance and the change in the drop peak transmission. Due to electro-refractive
effect of graphene a giant (>10 123) change in the effective index is demonstrated for the first
time on Si photonics waveguides and this large effect will crucially impact performances and
consumption of Si photonics devices. We confirmed the results by two independent
experiments involving two different gating schemes: Si gating through the ridge waveguide,
and polymer-electrolyte gating. Both the experiments demonstrate a very large phase effect in
good agreement with numerical calculations. The reported results validate the Kubo model
for the case of graphene-Si photonics interfaces and for propagation in this type of
waveguide. This is fundamental for the next design and fabrication of future graphene-silicon
photonics devices
High-responsivity graphene photodetectors integrated on silicon microring resonators.
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
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Identification of Novel Type 2 Diabetes Candidate Genes Involved in the Crosstalk between the Mitochondrial and the Insulin Signaling Systems
Type 2 Diabetes (T2D) is a highly prevalent chronic metabolic disease with strong co-morbidity with obesity and cardiovascular diseases. There is growing evidence supporting the notion that a crosstalk between mitochondria and the insulin signaling cascade could be involved in the etiology of T2D and insulin resistance. In this study we investigated the molecular basis of this crosstalk by using systems biology approaches. We combined, filtered, and interrogated different types of functional interaction data, such as direct protein–protein interactions, co-expression analyses, and metabolic and signaling dependencies. As a result, we constructed the mitochondria-insulin (MITIN) network, which highlights 286 genes as candidate functional linkers between these two systems. The results of internal gene expression analysis of three independent experimental models of mitochondria and insulin signaling perturbations further support the connecting roles of these genes. In addition, we further assessed whether these genes are involved in the etiology of T2D using the genome-wide association study meta-analysis from the DIAGRAM consortium, involving 8,130 T2D cases and 38,987 controls. We found modest enrichment of genes associated with T2D amongst our linker genes (p = 0.0549), including three already validated T2D SNPs and 15 additional SNPs, which, when combined, were collectively associated to increased fasting glucose levels according to MAGIC genome wide meta-analysis (p = 8.12×10−5). This study highlights the potential of combining systems biology, experimental, and genome-wide association data mining for identifying novel genes and related variants that increase vulnerability to complex diseases
Identification of novel type 2 diabetes candidate genes involved in the crosstalk between the mitochondrial and the insulin signaling systems
Type 2 Diabetes (T2D) is a highly prevalent chronic metabolic disease with strong co-morbidity with obesity and cardiovascular diseases. There is growing evidence supporting the notion that a crosstalk between mitochondria and the insulin signaling cascade could be involved in the etiology of T2D and insulin resistance. In this study we investigated the molecular basis of this crosstalk by using systems biology approaches. We combined, filtered, and interrogated different types of functional interaction data, such as direct protein-protein interactions, co-expression analyses, and metabolic and signaling dependencies. As a result, we constructed the mitochondria-insulin (MITIN) network, which highlights 286 genes as candidate functional linkers between these two systems. The results of internal gene expression analysis of three independent experimental models of mitochondria and insulin signaling perturbations further support the connecting roles of these genes. In addition, we further assessed whether these genes are involved in the etiology of T2D using the genome-wide association study meta-analysis from the DIAGRAM consortium, involving 8,130 T2D cases and 38,987 controls. We found modest enrichment of genes associated with T2D amongst our linker genes (p = 0.0549), including three already validated T2D SNPs and 15 additional SNPs, which, when combined, were collectively associated to increased fasting glucose levels according to MAGIC genome wide meta-analysis (p = 8.12×10(-5)). This study highlights the potential of combining systems biology, experimental, and genome-wide association data mining for identifying novel genes and related variants that increase vulnerability to complex diseases
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
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