Graphene has been proposed to be integrated with Si Photonics because of its very high mobility, fast carrier dynamics and ultra-broadband optical properties. High speed graphene photodetectors have been demonstrated so far, however the most are based on the photo-bolometric or photo-conductive effect. These devices are characterized by large dark current, in the order of milli-Amperes. Photothermal effect (PTE) photodetectors can be used in voltage detection mode with no dark current, it is ultra fast and it operates near zero-bias. Graphene PTE-based photodetectors have been reported so far but high-speed optical telecommunication signal detection has not been shown yet. Here, we report on a graphene PTE-based photodetector on SOI waveguide. Thanks to the optimized design we show a direct detection of 105Gb/s non-return to zero (NRZ) and 120Gb/s 4-level pulse amplitude modulation (PAM) optical signals.
The future global-scale quantum communication network will require free-space and satellite links able to work in daylight conditions and compatible with the telecom fiber infrastructure. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps. The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource for future satellite missions.
Graphene is a suitable material for optoelectronic applications that reveals several advantages and complementarities compared with other technologies. Graphene is a gapless material that absorbs radiation from visible to far-infrared and beyond including the terahertz range. The absorption can be modified by changing the material doping, i.e. Fermi level energy, by applying an external electric field. The change in absorption can be very fast and, for this reason, graphene can be used to realize optical modulators. Moreover, the absorption change occurs along with refractive index change. In particular, conditions, i.e. for Fermi level above the Pauli blocking, light is not absorbed anymore and only phase change occurs. Phase change has been demonstrated to be good for fast Mach Zehnder interferometer based modulation. The broadband absorption of Graphene is also exploited to realize efficient photodetectors. Generation of hot electrons upon light absorption in graphene is the cause of photo-thermal effect (PTE) that leads to photo voltage generation. PTE is an ultrafast process that is used for fast photodetection. In this work, the vision for graphene-based integrated photonics is presented. We review state-of-the-art graphene-based modulators and detectors and outline a roadmap matching the technology readiness requirements with the datacom and telecom market demands. We show that graphene-based integrated photonics could enable ultra-high spatial density, low power consumption for board and intra- data centre connectivity, access networks, metropolitan, core, regional and long-haul optical communications.
In this century of continuous exponential growth of communications worldwide, traditional electrical interconnection is finding increasingly difficult to respond to the bandwidth pressure, and photonic interconnection will most likely be the future standard.
Planar lightwave circuit (PLC) technology is capable of high-throughput fabrication of low loss waveguides, but is in general limited to its 2D geometry.
On the other hand femtosecond direct writing (FDW) provides a solid tool for the fabrication of optical circuits with great flexibility, exploiting its truly 3D properties, but suffers from higher losses and lower throughput.
By combining with PLC technology, FDW could aid in the bridging of different layers of optical circuits, exponentially decreasing their footprint. We report in this work the fabrication of such optical vias.
The fabrication of vertical waveguides in fused silica, using a IR femtosecond fiber laser, with parameters optimised to induce the previously reported micro-explosions mechanism inside fused silica. By using a
long working distance water immersion objective, we reduced spherical aberrations due to a better phase matching with the glass. A helix path was applied to create a cone of damaged material, leaving a stress-induced central waveguide, with propagation losses lower than 1 dB/mm.
Finally, we analyse the possibility of tilting these waveguides and its effect on their optical properties. This feature adds to the flexibility of this method, that could for example accommodate input/output angles of common coupling strategies used with PLC technologies.
Within the European Project TERABOARD, a photonic integration platforms including electronic-photonic integration is developed to demonstrate high bandwidth high-density modules and to demonstrate cost and energy cost target objectives. Large count high bandwidth density EO interfaces for onboard and intra-data center interconnection are reported. For onboard large count interconnections a novel concept based on optical-TSV interconnection platform with no intersections and no WDM multiplexing is reported. All input/output coupler arrays based on a pluggable silica platform are reported as well.
We propose a new dynamic range compression technique for infrared (IR) imaging systems that enhances details visibility and allows the control and adjustment of the image appearance by setting a number of tunable parameters. This technique adopts a bilateral filter to extract a details component and a coarse component. The two components are processed independently and then recombined to obtain the output-enhanced image that fits the display dynamic range. The contribution made is threefold. We propose a new technique for the visualization of high dynamic range (HDR) images that is specifically tailored to IR images. We show the effectiveness of the method by analyzing experimental IR images that represent typical area surveillance and object recognition applications. Last, we quantitatively assess the performance of the proposed technique, comparing the quality of the enhanced image with that obtained through two well-established visualization methods.
M. Romagnoli, L. Socci, L. Bolla, S. Ghidini, P. Galli, C. Rampinini, G. Mutinati, A. Nottola, A. Cabas, S. Doneda, M. Di Muri, R. Morson, T. Tomasi, G. Zuliani, S. Lorenzotti, D. Chacon, S. Marinoni, R. Corsini, F. Giacometti, S. Sardo, M. Gentili, G. Grasso
Silicon is the dominant material in the microelectronic industry and silicon photonics is rapidly gaining importance as a
technological platform for a wide range of applications in telecom, and optical interconnect. It allows the implementation
of many photonic functions through the use of wafer-scale technologies normally used for advanced CMOS-processing.
In this paper some of the most important issues toward a practical implementation of Silicon photonics into an industrial
device will be addressed: low loss waveguides, polarization handling, tunability, hitless switching. A tunable Add-Drop
multiplexer has been chosen as a case study of a fully integrated device.
The visualization of IR images on traditional display devices is often complicated by their high dynamic range.
Classical dynamic range compression techniques based on simple linear mapping, reduce the perceptibility of small
objects and often prevent the human observer from understanding some of the important details. Thus, more
sophisticated techniques are required to adapt the recorded signal to the monitor maintaining, and possibly
improving, object visibility and image contrast. The problem has already been studied with regard to images
acquired in the visible spectral domain, but it has been scarcely investigated in the IR domain. In this work, we
address this latter subject and propose a new method for IR dynamic range compression which stems from the
lesson learnt from existing techniques. First, we review the techniques proposed in the literature for contrast
enhancement and dynamic range compression of images acquired in the visible domain. Then, we present the new
algorithm which accounts for the specific characteristics of IR images. The performance of the proposed method are
studied on experimental IR data and compared with those yielded by two well established algorithms.
In this paper we study passive focusing techniques for infrared sensors. We present a survey of existing focus measures,
i.e. functionals that give an estimate of the quality of focus as a function of the lens position. We synthesize the material
proposed in the literature and show that all the approaches exploit the same general layout differing only for the choice
of the filtering technique used to extract the image details. We present and discuss experimental results obtained on real
infrared data taken in many operating conditions. The experimental analysis aims at comparing the quality of the focus
measures and at evaluating their impact of the subsequent algorithm that searches the best focus position of the lens. For
this purpose, we propose a comparative analysis based on three important properties of the focus measure: symmetry,
smoothness and peakdness.
The development of a compact and high performance MWIR step zoom camera based on the 640x480 staring focal
plane array (FPA) is described. The camera has a 20 magnification step zoom ranging between 24°x20° for the wide
field of view up to 1.2° x 1° for the narrow field of view and an aperture of F#4. The processing electronics is based on a
flexible and expandable architecture. Special emphasis is spent on the solutions adopted for the design of this high zoom
ratio and fast optics FLIR and on the electronic architecture and algorithms for image processing. An overview of the
performance is given.
Optically transparent nanostructured SiO2 glassceramics containing a high density of monodispersed, nanometer sized clusters of SnO2 were obtained by phase separation from sol-gel synthesized xerogel. This material was produced either as bulk samples or as thin films on silicon and it can be easily doped with rare earth ions during the sol-gel synthesis. Spectroscopic measurements were carried out on bulk samples, demonstrating an effective energy-transfer between nanoclusters and rare earth ions. A particular sol-gel derived synthesis was employed, producing silica-based films with relatively low electrical resistivity and thickness ranging between 300 and 1000 nm. Suitable sol features allowed thick single-step deposition by spin-coating techniques, assuring the homogeneous nanosized clustering of the semiconducting SnO2 phase. Refractive index and thickness were analyzed in films produced in different conditions of synthesis and thermal treatments of densification. The current-voltage response and the electro-induced optical emission in this material were investigated, suggesting potential technological applications in photonics and UV-emitting devices.
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