Juergen Schreiber

Imaging the universe in 3D with the VLT: the next-generation field spectrometer SPIFFI

We present SPIFFI, the integral field spectrometer for the VLT. This instrument allows simultaneous observation of IR spectra in more than 1000 image points of a 2D field. With its set of four gratings and a pixel scale that can be varied by a factor of ten, SPIFFI provides high flexibility, and at the same time offers the unique possibility of diffraction limited imaging spectroscopy at an 8m-class telescope, when fed by the adaptive optics system MACAO. We outline the scientific drivers for building such an instrument, the concept of image slicing, the optical design, and the implementation of SPIFFI.

On-sky performance of SPIFFI: the integral field spectrometer for SINFONI at the VLT

SPIFFI (SPectrometer for Infrared Faint Field Imaging) is a fully cryogenic, near-infrared imaging spectrograph built at the Max-Planck-Institute for Extraterrestrial Physics (MPE) and upgraded with a new detector and spectrograph camera by ASTRON/NOVA, ESO and MPE. The upgraded instrument will become a facility instrument for the ESO VLT in summer 2004 as part of the SINFONI (SINgle Faint Object Near-IR Investigation) project, which is the combination of SPIFFI and ESOs adaptive optics module MACAO (Multiple Application Curvature Adaptive Optics), at the Cassegrain focus of Yepun (UT4). In spring 2003 we had the opportunity to observe with SPIFFI as a guest instrument without the AO-module at the Cassegrain focus of UT2 of the VLT. In this paper we discuss the performance of SPIFFI during the guest-instrument phase. First we summarize the technical performance of SPIFFI like the spatial and spectral resolution, the detector performance and the instruments throughput. Afterwards we illustrate the power of integral field spectroscopy by presenting data and results of the Galactic Center.

SPIFFI image slicer: high-precision optics at cryogenic temperatures

SPIFFI is the near-infrared integral field spectrograph of the SINFONI VLT instrument. SPIFFI uses an image slicer with plane mirrors as its integral field unit. The integral field unit consists of two stacks of mirrors, each with 32 mirrors, rearranging a two-dimensional field-of-view of 32 x 32 pixels into a one-dimensional pseudo slit, which is fed into a long-slit spectrograph. The image slicer is constructed solely from Zerodur and is operated at a cryogenic temperature of 77 Kelvin. Only optical contacting is used for the assembly of the individual slicer mirrors and the image slicer on its base-plate. The special slicer mount holds the image slicer stress-free and compensates for the different thermal coefficients of expansion of the Zerodur image slicer and the Aluminium mount. Tests at room and cryogenic temperatures show the performance of the image slicer, the durability of the optical contacting technique, and the accuracy of the slicer mount.

New era of spectroscopy: SINFONI NIR integral field spectroscopy at the diffraction limit of an 8-m telescope

SINFONI, the SINgle Faint Object Near-IR Investigation, is an instrument for the very large telescope (VLT), which will start its operation mid 2002 and allow for the first time near IR integral field spectroscopy at the diffraction limit of an 8-m telescope. SINFONI is the combination of two state-of-the-art instruments, the integral field spectrometer SPIFFI, built by the Max-Planck-Institut fuer extraterrestrische Physik, and the adaptive optics system MACAO, built by the ESO. It will allow a unique type of observations by delivering simultaneously high spatial resolution and a moderate spectral resolution, where the higher spectral resolution mode will allow for software OH suppression. This opens new prospects for astronomy.

Green fluorescent nanodiamond conjugates and their possible applications for biosensing

Various nanoparticles play a prominent role in modern biosciences and medicine. Especially fluorescent cellular biomarkers are a prospective material for diagnostics and therapy. Nevertheless, most of the available biomarkers have some drawbacks due to either physical and optical or cytotoxic properties. Here we investigated the potential of green fluorescent nanodiamonds as extra- and intracellular biomarkers for living cells. We characterized the structure of the used detonation synthesized nanodiamonds (DND) by X-ray diffraction (XRD) and the optical properties by fluorescence and infrared spectroscopy. For the extracellular attachment the nanodiamonds were functionalized by attaching antibodies that target extracellular structures such as membrane. Transfections were mediated by dendrimers, cationic liposomes and protamine sulfate. Using fluorescence microscopy, we confirmed successful extracellular binding on and transfection of the nanodiamonds into prostate cancer cells. Furthermore, nanodiamonds can be targeted selectively to intracellular structures. Therefore, nanodiamonds are a promising tool for biosensing.

Advances in Barkhausen noise analysis

The magnetic Barkhausen Noise technique is a well suited method for the characterization of ferromagnetic materials. The Barkhausen effect results in an interaction between the magnetic structure and the microstructure of materials, and is sensitive to the stresses and microstructure related mechanical properties. Barkhausen noise is a complex signal that provides a large amount of information, for example frequency spectrum, amplitude, RMS value, dependence of magnetic field strength, magnetization frequency and fractal behavior. Although this technique has a lot potentials, it is not commonly used in nondestructive material testing. Large sensors and complex calibration procedures made the method impractical for many applications. However, research has progressed in recent years; new sensor designs were developed and evaluated, new algorithms to simplify the calibration and measurement procedures were developed as well as analysis of additional material properties have been introduced.

Material characterization by laser speckle photometry

The damage and stress conditions of large industrial components have to be tested continuously. Especially welding processes in the field of coal production demand a nondestructive monitoring of internal stresses under an external load. In a first step, a new optical method, Laser Speckle Photometry was used during laboratory welding experiments under tensile and bending loads at high strength construction steels. Laser Speckle Photometry is a fast and contactless method for measuring spatial-temporal dynamics of speckle field with high temporal resolution after local heat excitation. The thermally induced change in the material structure causes changes in the speckle-field, which is formed by a probing laser. The shift of the speckle-field is analyzed by statistical methods, using correlation functions. The result of processing is the two-dimensional distribution of thermal diffusivity coefficient correlated to porosity, materials strain or hardness [1-3]. Here, the results of the welding experiments under load are presented. It is shown, that the Laser Speckle Photometry is a suitable technique for nondestructive monitoring and characterization of internal material stresses under external load.