Lasers for LISA: Overview and phase characteristics

We have investigated two alternative laser systems for the Laser Interferometer Space Antenna (LISA). One consisted of the laser of LISA's technology precursor LISA Pathfinder and a fiber amplifier originally designed for a laser communication terminal onboard TerraSar-X. The other consisted of a commercial fiber distributed feedback (DFB) laser seeding a fiber amplifier. We have shown that the TerraSar-X amplifier can emit more than 1W without the onset of stimulated Brillouin scattering as required by LISA. We have measured power noise and frequency noise of the LISA Pathfinder laser (LPL) and the fiber laser. The fiber laser shows comparable or even lower power noise than the LPL. LISA will use electro-optical modulators (EOMs) between seed laser and amplifier for clock noise comparison between spacecraft. This scheme requires that the excess noise added by the amplifiers be negligible. We have investigated the phase characteristics of two fiber amplifiers emitting 1 W and found them to be compatible with the LISA requirement on amplifier differential phase noise.DLR/50 OQ 0501DLR/50 OQ 060

Optical bench development for LISA

For observation of gravitational waves at frequencies between 30 μHz and 1 Hz, the LISA mission will be implemented in a triangular constellation of three identical spacecraft, which are mutually linked by laser interferometry in an active transponder scheme over a 5 million kilometer arm length. On the end point of each laser link, remote and local beam metrology with respect to inertial proof masses inside the spacecraft is realized by the LISA Optical Bench. It implements further- more various ancillary functions such as point-ahead correction, acquisition sensing, transmit beam conditioning, and laser redundancy switching. A comprehensive design of the Optical Bench has been developed, which includes all of the above mentioned functions and at the same time ensures manufacturability on the basis of hydroxide catalysis bonding, an ultrastable integration technology already perfected in the context of LISA's technology demonstrator mission LISA Pathfinder. Essential elements of this design have been validated by dedicated pre-investigations. These include the demonstration of polarizing heterodyne interferometry at the required Picometer and Nanoradian performance levels, the investigation of potential non-reciprocal noise sources in the so-called backlink fiber, as well as the development of a laser redundancy switch breadboard

Interferometric Space Missions for the Search for Terrestrial Exoplanets: Requirements on the Rejection Ratio

The requirements on space missions designed to study Terrestrial exoplanets are discussed. We then investigate whether the design of such a mission, specifically the Darwin nulling interferometer, can be carried out in a simplified scenario. The key element here is accepting somewhat higher levels of stellar leakage. We establish detailed requirements resulting from the scientific rationale for the mission, and calculate detailed parameters for the stellar suppression required to achieve those requirements. We do this utilizing the Darwin input catalogue. The dominating noise source for most targets in this sample is essentially constant for all targets, while the leakage diminishes with the square of the distance. This means that the stellar leakage has an effect on the integration time only for the nearby stars, while for the more distant targets its influence decreases significantly. We assess the impact of different array configurations and nulling profiles and identify the stars for which the detection efficiency can be maximized.Comment: 21 pages, 8 figures; TBP in Astrophysics and Space Science 200

DC readout experiment in Enhanced LIGO

The two 4 km long gravitational wave detectors operated by the Laser Interferometer Gravitational-wave Observatory (LIGO) were modified in 2008 to read out the gravitational wave channel using the DC readout form of homodyne detection and to include an optical filter cavity at the output of the detector. As part of the upgrade to Enhanced LIGO, these modifications replaced the radio-frequency (RF) heterodyne system used previously. We describe the motivations for and the implementation of DC readout and the output mode cleaner in Enhanced LIGO. We present characterizations of the system, including measurements and models of the couplings of the noises from the laser source to the gravitational wave readout channel. We show that noise couplings using DC readout are improved over those for RF readout, and we find that the achieved shot-noise-limited sensitivity is consistent with modeled results

Frequency stabilization and actuator characterization of an ytterbium-doped distributed-feedback fiber laser for LISA

We have investigated an ytterbium-doped distributed-feedback fiber master oscillator power amplifier system emitting 1 W and its suitability for the space-borne interferometric gravitational-wave detector Laser Interferometer Space Antenna (LISA). For this purpose we measured the laser system's free-running frequency noise, characterized its frequency actuator, and implemented a robust frequency stabilization. Up to 100 Hz Fourier frequency the free-running frequency, noise was comparable to that of a nonplanar ring oscillator. The first resonance of the actuator was at 32 kHz with a quality factor of 26 and a delay of 20 mu s. The frequency lock to a thermally shielded Fabry-Perot cavity was stable over many hours and fulfilled the LISA requirements. (C) 2009 Optical Society of Americ

1 ASTROPHYSICAL IMAGING WITH THE DARWIN IR INTERFEROMETER

The proposed infrared space interferometry mission Darwin has two main aims: (i) to detect and characterize exo-planets similar to the Earth, and (ii) to carry out astrophysical imaging in the wavelength range 6- 20 micron at a sensitivity similar to JWST, but at an angular resolution up to 100 times higher. In this contribution we will first briefly discuss the imaging performance of the Darwin mission. We will then discuss how Darwin will contribute in a very significant way to our understanding of the formation and evolution of planets, stars, galaxies, and supermassive black-holes located at the centers of galaxies. Key words: instrumentation: interferometers; infrared: general; stars: formation; galaxies: active; galaxies: evolution. 1

Delft testbed interferometer: layout design and research goals

The Delft Testbed Interferometer (DTI) will be presented. The main purpose for the DTI is to demonstrate the feasibility of homothetic mapping, both fixed and under scanning conditions. The driving design issues behind the DTI will be presented together with a list of experiments to be conducted with the DTI system in the field of wide field imaging

Influence of atmospheric turbulence on the performance and design of GENIE

International audienc

Influence of atmospheric turbulence on the performance and design of GENIE

International audienc