107 research outputs found

    Roadmap on all-optical processing

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    The ability to process optical signals without passing into the electrical domain has always attracted the attention of the research community. Processing photons by photons unfolds new scenarios, in principle allowing for unseen signal processing and computing capabilities. Optical computation can be seen as a large scientific field in which researchers operate, trying to find solutions to their specific needs by different approaches; although the challenges can be substantially different, they are typically addressed using knowledge and technological platforms that are shared across the whole field. This significant know-how can also benefit other scientific communities, providing lateral solutions to their problems, as well as leading to novel applications. The aim of this Roadmap is to provide a broad view of the state-of-the-art in this lively scientific research field and to discuss the advances required to tackle emerging challenges, thanks to contributions authored by experts affiliated to both academic institutions and high-tech industries. The Roadmap is organized so as to put side by side contributions on different aspects of optical processing, aiming to enhance the cross-contamination of ideas between scientists working in three different fields of photonics: optical gates and logical units, high bit-rate signal processing and optical quantum computing. The ultimate intent of this paper is to provide guidance for young scientists as well as providing research-funding institutions and stake holders with a comprehensive overview of perspectives and opportunities offered by this research field

    Optically pumped planar waveguide lasers, part I: fundamentals and fabrication techniques

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    The tremendous interest in the field of waveguide lasers in the past two decades is largely attributed to the geometry of the gain medium, which provides the possibility to store optical energy on a very small dimension in the form of an optical mode. This allows for realization of sources with enhanced optical gain, low lasing threshold, and small footprint and opens up exciting possibilities in the area of integrated optics by facilitating their on-chip integration with different functionalities and highly compact photonic circuits. Moreover, this geometrical concept is compatible with high-power diode pumping schemes as it provides exceptional thermal management, minimizing the impact of thermal loading on laser performance. The proliferation of techniques for fabrication and processing capable of producing high optical quality waveguides has greatly contributed to the growth of waveguide lasers from a topic of fundamental research to an area that encompasses a variety of practical applications. In this first part of the review on optically pumped waveguide lasers the properties that distinguish these sources from other classes of lasers will be discussed. Furthermore, the current state-of-the art in terms of fabrication tools used for producing waveguide lasers is reviewed from the aspects of the processes and the materials involved

    Fabrication and characterisation of tellurite planar waveguides

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    Tellurite glasses, which contain Tellurium dioxide as the main component, have some remarkable optical properties which are well recognised and exploited in the bulk optics and fibre fields. They include a high acousto-optic figure of merit, wide mid infrared transparency, the highest optical nonlinearity amongst oxides, and excellent rare earth hosting, etc. Despite these attractive properties, until now, no one has succeeded in fabricating low loss planar waveguides in these materials. This work develops high quality optical planar waveguides in Tellurium dioxide for the first time. The project investigates the materials science for optical Tellurium dioxide films and discovers an appropriate waveguide fabrication method. The thin films have been fabricated by reactive radio frequency magnetron sputtering using a Tellurium target in an oxygen and argon atmosphere. Propagation losses at 1550nm in the planar films are 0.1dB/cm or lower in stoichiometric composition. The properties of films have been also found to be stable with thermal annealing up to 300 degree Celsius. Plasma etching of tellurite glasses has been systematically studied. High quality etching of Tellurium dioxide and chalcogenide glass films has been demonstrated with a Methane/Hydrogen/Argon gas mixture. As a result, a fabrication recipe which produces low loss (0.1dB/cm) planar waveguides has been discovered. The nonlinear coefficient of the sputtered TeO2 has been characterised by self-phase modulation (SPM) experiments and the second order nonlinear coefficient has been measured to be around 25 times that of silica. Significant signal conversion, -4dB, has achieved with large bandwidth of 30nm in the four-wave mixing (FWM) experiment pumped at 1550nm in a slightly normal dispersion waveguide. Erbium doped Tellurium oxide thin films have also been fabricated by co-sputtering of Erbium and Tellurium targets into an Oxygen and Argon atmosphere. The obtained films have been found to have good properties for Erbium doped waveguide amplifiers. The Erbium concentration can be controlled within the range of interest with Erbium/Tellurium ratios ranging from 0.1% to 3% or more. The 1.5 micrometre photoluminescence properties of the films are excellent with effective bandwidth of more that 60nm and intrinsic lifetime of order of 3ms. Despite the fact that there was OH contamination in the films, single mode Erbium doped waveguide amplifiers with high internal gain have been successfully obtained. The 1480nm pumped amplifier achieved internal gain from below 1520nm to beyond 1600nm. The peak gain of 2.8dB/cm and 40nm 3dB gain bandwidth have been accomplished. These results are a major stepping stone towards ""system-on-chip"" optical applications for telecom and mid infrared optics given the multifunctional nature of tellurite materials. -- provided by Candidate
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