We report an electrolyte-gated single layer graphene super-capacitor, embedded in a polyethylene-on-Au Salisbury mirror optical architecture, working as a THz frequency modulator. The gate-tunable single layer graphene in a quarter wave waveguide ensures 40% optical amplitude modulation depth, and saturable absorption mirror operation, with similar to 4.5 Wcm(-2) saturation intensity. By coupling the modulator with a THz quantum cascade laser frequency comb in an external cavity configuration, we also demonstrate fine-tuning of the intermode beatnote frequency, revealing a promising perspective for metrological sources requiring a tight frequency control of the intermode comb frequency

Mirrors are a subset of optical components essential for the success of current and future space missions. Most of the telescopes for space programs ranging from earth observation to astrophysics and covering the whole electromagnetic spectrum from x-rays to far-infrared are based on reflective optics. Mirrors operate in diverse and harsh environments that range from low-earth orbit to interplanetary orbits and deep space. The operational life of space observatories spans from minutes (sounding rockets) to decades (large observatories), and the performance of the mirrors within the mission lifetime is susceptible to degrading, resulting in a drop in the instrument throughput, which in turn affects the scientific return. Therefore, the knowledge of potential degradation mechanisms, how they affect mirror performance, and how to prevent them is of paramount importance to ensure the long-term success of space telescopes. In this review, we report an overview of current mirror technology for space missions with a focus on the importance of the degradation and radiation resistance of coating materials. Special attention is given to degradation effects on mirrors for far and extreme UV, as in these ranges the degradation is enhanced by the strong absorption of most contaminants.

Silicon-based digital electronics have evolved over decades through an aggressive scaling process following Moore's law with increasingly complex device structures. Simultaneously, large-area electronics have continued to rely on the same field-effect transistor structure with minimal evolution. This limitation has resulted in less than ideal circuit designs, with increased complexity to account for shortcomings in material properties and process control. At present, this situation is holding back the development of novel systems required for printed and flexible electronic applications beyond the Internet of Things. In this work we demonstrate the opportunity offered by the source-gated transistor's unique properties for low-cost, highly functional large-area applications in two extremely compact circuit blocks. Polysilicon common-source amplifiers show 49 dB gain, the highest reported for a two-transistor unipolar circuit. Current mirrors fabricated in polysilicon and InGaZnO have, in addition to excellent current copying performance, the ability to control the temperature dependence (degrees of positive, neutral or negative) of output current solely by choice of relative transistor geometry, giving further flexibility to the design engineer. Application examples are proposed, including local amplification of sensor output for improved signal integrity, as well as temperature-regulated delay stages and timing circuits for homeostatic operation in future wearables. Numerous applications will benefit from these highly competitive compact circuit designs with robust performance, improved energy efficiency and tolerance to geometrical variations: sensor front-ends, temperature sensors, pixel drivers, bias analog blocks and high-gain amplifiers.

A set of components will he installed during ITER fist plasma operation to protect the vacuum vessel and other in vessel auxiliary systems from the plasma and from the stray radiation injected at the Electron Cyclotron harmonics to generate breakdown and sustain burn-through. This paper focuses on the quasi-optical design of the system of three mirrors redirecting the microwave beams coming from the Electron Cyclotron Resonance Heating (ECRH) upper launcher to the plasma resonance after proper shaping. In particular, the system consists of two shaped mirrors and one grating mirror. The non absorbed EC power is then intercepted and absorbed into a beam dump located in one equatorial port.

The preliminary design of a polychromator unit for a Raman lidar (Light Detection And Ranging) for atmospheric calibration in the framework of the Cherenkov Telescope Array (CTA) project is presented. To obtain high quality data from CTA, a precise monitoring of the atmospheric transmission is needed. Remote-sensing instruments, like elastic/Raman lidars, have already been proven a powerful tool in environmental studies, and a lidar installed and operated at the CTA site is foreseen for correcting systematic biases on the energy and flux. The lidar we discuss here consists of a powerful laser that emits light pulses into the atmosphere, a mirror of 1.8 m diameter that collects the backscattered light and a polychromator unit where the light is analyzed. The laser is a pulsed Nd:YAG with the first two harmonics available at 355 and 532 nm and the polychromator has 4 read-out channels: two to analyze the elastic backscattering at 355 and 532 nm and two for the Raman Nitrogen back-scattered light, at 387 and 607 nm, respectively. The polychromator module needs to collect the majority of the light coming from the telescope, to split the different wavelengths and to focus the beams onto photomultiplier detectors. The collection and focalization of the beams are done by means of simple lens-couples and the separation with custom-made dichroic mirrors and narrow-band filters. The performance of the conceived optical design, the adopted design choices for the glass, surface figure and size of the lenses, and the expected throughput for the different channels are hereafter described. © 2012 SPIE.

METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS, the "Multi Element Telescope for Imaging and Spectroscopy", is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The mission profile will bring the Solar Orbiter spacecraft as close to the Sun as 0.3 A.U., and up to 35? out-of-ecliptic providing a unique platform for helio-synchronous observations of the Sun and its polar regions. METIS coronagraph is designed for multi-wavelength imaging and spectroscopy of the solar corona. This presentation gives an overview of the innovative design elements of the METIS coronagraph. These elements include: i) multi-wavelength, reflecting Gregorian-Telescope; ii) multilayer coating optimized for the extreme UV (30.4 nm, HeII Lyman-?) with a reflecting cap-layer for the UV (121.6 nm, HI Lyman-?) and visible-light (590-650); iii) inverse external-occulter scheme for reduced thermal load at spacecraft peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror to feed a 1st and 4th-order spherical varied line-spaced (SVLS) grating placed on a section of the secondary mirror; v) liquid crystals electro-optic polarimeter for observations of the visible-light K-corona. The expected performances are also presented. © 2012 SPIE.

We report the programmable pulse shaping of ultrabroadband pulses by the use of a novel design of electrostatic deformable mirror based on push pull technology. We achieved the formation of double and triple pulses with programmable delay and a pulse length of 20fs@1.3?m with spectrum tunability. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Rosetta is one of the cornerstone missions of the European Space Agency for having a roundez-vous with the periodic comet P/Wirtanen in 2011. One of the imaging instruments on board the satellite is the Wide Angle Camera, a cooperation among several european institutes. This camera adopts an all reflecting, unvignetted unobstructed two mirror configuration which allows to cover a 12° × 12° Field of View with an F/5.6 aperture and an optical quality better than 80% geometrical ensquared energy inside approximately 20 arcsec. The flight model of this camera has been successfully integrated and tested in our laboratories and finally has been integrated on the satellite. In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results.

Rosetta is the cornerstone mission of ESA devoted to the study of minor bodies of Solar System. The mission will be launched on January 2003 and has the rendez-vous with 46P/Wirtanen comet (on November 2011) as primary target. The final aim of the mission will be a better understanding of the formation and composition of early Solar System and of its evolution over the last 4.5 billion years. Rosetta has a complex instrumentation devoted both to remote sensing and to in situ investigation. The authors were involved in the design and manufacturing of the Wide Angle Camera (WAC) of the OSIRIS imaging system. The WAC has a very peculiar optical system based on two aspherical mirrors in an off axis configuration, and will be principally devoted to the study of the very faint gas and dust cometary features. To reach this goal an innovative baffling system was designed and constructed in order to obtain the stray-light suppression requirements for source both inside and outside the field of view of the camera. In particular a contrast ratio of 10-4 inside the field of view is needed in order to detect gaseous and dusty features close to the nucleus of the comet. In this paper the process of baffling design and manufacturing is described: the behavior of the baffle, previously calculated by numerical simulations from the mechanical and optical points of view, was assessed both for the single components and for the complete assembly as described in this paper.

In this letter, we present a novel structure for light amplitude modulation based on a lateral p-i-n diode combined with a Bragg reflector which transforms the phase shift induced by the plasma dispersion effect in the intrinsic region of the diode into a voltage controlled variation of the reflectivity of the Bragg mirror. Numerical simulations show a modulation depth of 50% achieved in about 12 ns with a power dissipation of 4.0 mW and an insertion loss of 1.0 dB. The device is demonstrated to be very attractive in terms of power dissipation as compared to a Mach-Zehnder interferometer occupying the same area on chip. © 1997 American Institute of Physics.