6 research outputs found
All-optical free-space routing of upconverted light by metasurfaces via nonlinear interferometry
All-optical modulation yields the promise of high-speed information
processing. In this frame, metasurfaces are rapidly gaining traction as
ultrathin multifunctional platforms for light management. Among the featured
functionalities, they enable light wavefront manipulation and, more recently,
demonstrated the ability to perform light-by-light manipulation through
nonlinear optical processes. Here, by employing a nonlinear periodic
metasurface, we demonstrate all-optical routing of telecom photons upconverted
to the visible range. This is achieved via the interference between two
frequency-degenerate upconversion processes, namely third-harmonic and
sum-frequency generation, stemming from the interaction of a pump pulse with
its frequency-doubled replica. By tuning the relative phase and polarization
between these two pump beams, and concurrently engineering the nonlinear
emission of the individual elements of the metasurfaces (meta-atoms) along with
its pitch, we route the upconverted signal among the diffraction orders of the
metasurface with a modulation efficiency up to 90%. Thanks to the phase control
and the ultrafast dynamics of the underlying nonlinear processes, free-space
all-optical routing could be potentially performed at rates close to the
employed optical frequencies divided by the quality factor of the optical
resonances at play. Our approach adds a further twist to optical
interferometry, which is a key-enabling technique in a wide range of
applications, such as homodyne detection, radar interferometry, LiDAR
technology, gravitational waves detection, and molecular photometry. In
particular, the nonlinear character of light upconversion combined with phase
sensitivity is extremely appealing for enhanced imaging and biosensing.Comment: 18 pages, 6 figure
Last results of technological developments for ultra-lightweight, large aperture, deployable mirror for space telescopes
The aim of this work is to describe the latest results of new technological concepts for Large Aperture Telescopes Technology (LATT) using thin deployable lightweight active mirrors. This technology is developed under the European Space Agency (ESA) Technology Research Program and can be exploited in all the applications based on the use of primary mirrors of space telescopes with large aperture, segmented lightweight telescopes with wide Field of View (FOV) and low f/#, and LIDAR telescopes. The reference mission application is a potential future ESA mission, related to a space borne DIAL (Differential Absorption Lidar) instrument operating around 935.5 nm with the goal to measure water vapor profiles in atmosphere. An Optical BreadBoard (OBB) for LATT has been designed for investigating and testing two critical aspects of the technology: 1) control accuracy in the mirror surface shaping. 2) mirror survivability to launch. The aim is to evaluate the effective performances of the long stroke smart-actuators used for the mirror control and to demonstrate the effectiveness and the reliability of the electrostatic locking (EL) system to restraint the thin shell on the mirror backup structure during launch. The paper presents a comprehensive vision of the breadboard focusing on how the requirements have driven the design of the whole system and of the various subsystems. The manufacturing process of the thin shell is also presented
Technological developments for ultra-lightweight, large aperture, deployable mirror for space telescopes
The increasing interest on space telescopes for scientific applications leads to implement the manufacturing technology of the most critical element, i.e. the primary mirror: being more suitable a large aperture, it must be lightweight and deployable. The presented topic was originally addressed to a spaceborne DIAL (Differential Absorption LIDAR) mission operating at 935.5 nm for the measurement of water vapour profile in atmosphere, whose results were presented at ICSO 2006 and 2008. Aim of this paper is to present the latest developments on the main issues related to the fabrication of a breadboard, covering two project critical areas identified during the preliminary studies: the design and performances of the long-stroke actuators used to implement the mirror active control and the mirror survivability to launch via Electrostatic Locking (EL) between mirror and backplane. The described work is developed under the ESA/ESTEC contract No. 22321/09/NL/RA. The lightweight mirror is structured as a central sector surrounded by petals, all of them actively controlled to reach the specified shape after initial deployment and then maintained within specs for the entire mission duration. The presented study concerns: a) testing the Carbon Fiber Reinforced Plastic (CFRP) backplane manufacturing and EL techniques, with production of suitable specimens; b) actuator design optimisation; c) design of the deployment mechanism including a high precision latch; d) the fabrication of thin mirrors mock-ups to validate the fabrication procedure for the large shells. The current activity aims to the construction of an optical breadboard capable of demonstrating the achievement of all these coupled critical aspects: optical quality of the thin shell mirror surface, actuators performances and back-plane - EL subsystem functionality
The LATT way towards large active primaries for space telescopes
The Large Aperture Telescope Technology (LATT) goes beyond the current paradigm of future space telescopes, based on a deformable mirror in the pupil relay. Through the LATT project we demonstrated the concept of a low-weight active primary mirror, whose working principle and control strategy benefit from two decades of advances in adaptive optics for ground-based telescopes. We developed a forty centimeter spherical mirror prototype, with an areal density lower than 17 kg/m2, controlled through contactless voice coil actuators with co-located capacitive position sensors. The prototype was subjected to thermo-vacuum, vibration and optical tests, to push its technical readiness toward level 5. In this paper we present the background and the outcomes of the LATT activities under ESA contract (TRP programme), exploring the concept of a lightweight active primary mirror for space telescopes. Active primaries will open the way to very large segmented apertures, actively shaped, which can be lightweight, deployable and accurately phased once in flight
Laboratory demonstration of a primary active mirror for space with the LATT: large aperture telescope technology
The LATT project is an ESA contract under TRP programme to demonstrate the scalability of the technology from ground-based adaptive mirrors to space active primary mirrors. A prototype spherical mirror based on a 40 cm diameter 1 mm thin glass shell with 19 contactless, voice-coil actuators and co-located position sensors have been manufactured and integrated into a final unit with an areal density lower than 20 kg/m2. Laboratory tests demonstrated the controllability with very low power budget and the survival of the fragile glass shell exposed to launch accelerations, thanks to an electrostatic locking mechanism; such achievements pushes the technology readiness level toward 5. With this prototype, the LATT project explored the feasibility of using an active and lightweight primary for space telescopes. The concept is attractive for large segmented telescopes, with surface active control to shape and co-phase them once in flight. In this paper we will describe the findings of the technological advances and the results of the environmental and optical tests
Coherent all-optical steering of upconverted light by a nonlinear metasurface
In recent years a strong drive towards the miniaturization of nonlinear optics has been motivated by the functionalities it could empower in integrated devices. Among these, the upconversion of near-infrared photons to the visible and their manipulation is fundamental to downscale optical information. We propose a dual-beam scheme whereby a pulse at the telecom frequency ω (1550 nm wavelength) is mixed with its frequency-doubled replica at 2ω. When the two pump pulses are superimposed on a nonlinear, all-dielectric metasurface two coherent frequency-tripling pathways are excited: third-harmonic generation (THG, ω+ω+ω) and sum-frequency generation (SFG, ω+2ω). Their coherent superposition at 3ω produces interference, which we enable by filtering the k-space with the metasurface diffraction. The steering of the emission among diffraction orders, is sensitive to the relative phase between the two pumps. Therefore, by exploiting the phase as a tuning knob, the upconverted signal can be switched between diffraction orders with an efficiency >90%. The proposed approach can be envisioned as an all-optical method to reroute upconverted telecom photons