Domenico Bonaccini

Analysis of isoplanatic high resolution stellar fields by the StarFinder code

We describe a new code for the deep analysis of stellar fields, designed for Adaptive Optics Nyquist-sampled images with high and low Strehl ratio. The Point Spread Function is extracted directly from the image frame, to take into account the actual structure of the instrumental response and the atmospheric effects. The code is written in IDL language and organized in the form of a self-contained widget-based application, provided with a series of tools for data visualization and analysis. A description of the method and some applications to AO data are presented.

ESO VLT laser guide star facility

We report in this paper on the design and progress of the ESO Laser Guide Star Facility. The project will create a user facility embedded in UT4, to produce in the Earths Mesosphere Laser Guide Stars, which extend the sky coverage of Adaptive Optics systems on the VLT UT4 telescope. Embedded into the project are provisions for multiple LGS to cope with second generation MCAO instruments.

ARNICA, THE ARCETRI NEAR-INFRARED CAMERA

ARNICA (ARcetri Near-Infrared CAmera) is the imaging camera for the near-infrared bands between 1.0 and 2.5 microns that the Arcetri Observatory has designed and built for the Infrared Telescope TIRGO located at Gornergrat, Switzerland. We describe the mechanical and optical design of the camera, and report on the astronomical performance of ARNICA as measured during the commissioning runs at the TIRGO (December, 1992 to December 1993), and an observing run at the William Herschel Telescope, Canary Islands (December, 1993). System performance is defined in terms of efficiency of the camera+telescope system and camera sensitivity for extended and point-like sources.

SINFONI: a near-infrared AO-assisted integral field spectrometer for the VLT

SINFONI, the SINgle Faint Object Near-IR Investigation, is an instrument for the very large telescope, designed to provide spectroscopy at the telescope diffraction limit in the near-IR. This unique capability is achieved by combining two state-of-the-art developments, an integral field spectrometer and a curvature sensor based adaptive optics system. SINFONI is a collaborative effort by the Max-Planck- Institut fuer extraterrsetrische Physik and the European Southern Observatory.

The VLT laser guide star facility

We report on the ongoing VLT Laser Guide Star Facility project, which will allow the ESO UT4 telescope to produce an artificial reference star for the Adaptive Optics systems NAOS-CONICA and SINFONI. A custom developed dye laser producing >10W CW at 589nm is installed on-board of the UT4 telescope, then relayed by means of a single mode optical fiber behind the secondary mirror, where a 500mm diameter lightweight, f/1 launch telescope is projecting the laser beam at 90 km altitude. We described the design tradeoffs and provide some details of the chosen subsystems. This paper is an update including subsystems results, to be read together with our previous paper on LGSF design description.

MACAO and its application for the VLT Interferometer

The European Southern Observatory is developing a medium order curvature adaptive optics system designed to be operable with minimal modification at any focus of the Very Large telescope (VLT). The first application of this AO system (MACAO) is to equip all four VLT Unit Telescope (UT) Coude foci with 60 element AO systems capable of delivering to the VLT Interferometer (VLTI) > 50% K band Strehl. The AO system being used by an interferometer is constrained to introduce minimal piston and operating as a sub-system of a large and complex instrument to have a robust architecture and simple operation. Installation of the first AO system is scheduled to begin first Quarter 2002 with completion of all four UTs by early 2004. Other applications of the MACAO system will be for use by the CRIRES and SPIFFI spectrographs.

High-power 938-nm cladding pumped fiber laser

We have developed a Nd:doped cladding pumped fiber amplifier, which operates at 938nm with greater than 2W of output power. The core co-dopants were specifically chosen to enhance emission at 938nm. The fiber was liquid nitrogen cooled in order to achieve four-level laser operation on a laser transition that is normally three level at room temperature, thus permitting efficient cladding pumping of the amplifier. Wavelength selective attenuation was induced by bending the fiber around a mandrel, which permitted near complete suppression of amplified spontaneous emission at 1088nm. We are presently seeking to scale the output of this laser to 10W. We will discuss the fiber and laser design issues involved in scaling the laser to the 10W power level and present our most recent results.

Compact fiber laser approach to generating 589 nm laser guide stars

We are developing an all-fiber laser system for generating 589 nm light for laser-guided adaptive optics. If only natural stars can be used to measure the turbulence in the Earths atmosphere, at most a few percent of the sky is accessible to adaptive optics correction. Laser guide stars are therefore crucial to the broad use of adaptive optics, because they facilitate access to a large fraction of possible locations on the sky. In particular, lasers tuned to the 589 nm resonance line of atomic sodium are able to create an artificial beacon at altitudes of 95-105 km, thus coming as close as possible to reproducing the light path of starlight. The deployment of multiconjugate adaptive optics on large aperture telescopes world-wide will require the use of three to five sodium laser guide stars in order to achieve uniform correction over the aperture with a high Strehl value. Current estimates place the minimum required laser power at 10 W per laser for a continuous wave source. In addition, the lasers need to be compact, efficient, robust and turnkey.

Scalable 11W 938nm Nd3+ doped fiber laser

11W of 938nm light was produced in an Nd3+ fiber laser. Optimization of the ratio of the fiber core and cladding areas permitted operation of the laser at room temperature by minimizing 1088nm gain.

Fiber Raman laser development for multiple sodium laser guide star adaptive optics

We report on our research to develop a fiber Raman laser for multiple sodium laser guide star adaptive optics. Our goal is a fiber laser source at 589 nm with a diffraction-limited continuous-wave output power of at least 10 W and a linewidth of less than 3 GHz. In this paper we present and model our concept of a frequency-doubled fiber Raman amplifier. Recent advances in commercially available pump and seed laser technologies are making the amplifier approach a highly attractive solution for a turn-key sodium-guide star laser system.