Showing papers by "Uwe Griebner published in 2001"

Spatially resolved small-angle noncollinear interferometric autocorrelation of ultrashort pulses with microaxicon arrays.

Abstract: Small-angle, noncollinear, first- and second-order interferometric autocorrelation experiments with Ti:sapphire laser pulses of 9-80-fs duration have been performed with microaxicon arrays. Predictions of short-pulse spatial frequency effects were verified by comparison of interference patterns of single elements and matrices. An angular spectrum of Gaussian-shaped axicons was analyzed on the basis of linear refraction. Experimental data indicate contributions to autocorrelation by nonlinear refraction and travel-time differences. The influence of the spectral bandwidth was separated from the pulse-duration-dependent effects. Spatially resolved information about the coherence time was delivered by the multichannel structure.

Design, characterization, and applications of multilayer micro-optics

Abstract: Multilayer micro-optics combines refractive beam shaping with wavelength selective multiple interference. Layer composition and thickness distribution were optimized by advanced simulation software. Components were fabricated by mask-shaded vapor deposition with planetary rotation. Surface profiles were characterized interferometrically. For two-dimensional reflectance mapping, a high-accuracy automated system was developed. Micro-mirror arrays for self-imaging resonators, mode selective mirrors for miniaturized solid-state lasers and angular-adapted graded AR-coatings for microlenses are presented as applications.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Method and arrangement for spatially resolved and time-resolved interferometric characterization of ultrashort laser pulses

Abstract: Disclosed in a method and arrangement for performing a spatially resolved non-collinear measurement of the autocorrelation function of the first or higher order by means of a matrix of beam shaping individual elements, such that there is a local splitting of the beam into a beam matrix of conical component beams, where each component beam represents spatially integrated information regarding the partial area of the matrix through which it passes, the interference resolution is thus determined by the matrix geometry, and the interference pattern produced in space by each component beam in a certain plane imaged on a matrix camera supplies an autocorrelation function of the first order or, by utilizing non-linear interactions in a suitable medium, of a higher order accordingly, so that the coherence time or the pulse period of individual laser pulses or trains of multiple laser pulses can be determined as a function of location.

Verfahren und Anordnung zur orts- und zeitaufgelösten interferometrischen Charakterisierung von ultrakurzen Laserimpulsen

Abstract: Die Erfindung betrifft Verfahren und eine Anordnung zur orts- und zeitaufgelosten Charakterisierung von ultrakurzen Laserimpulsen. Die Aufgabe der Erfindung, gattungsgemase Verfahren und eine Anordnung zu entwickeln, mit denen die beschriebenen Nachteile des Standes der Technik vermieden werden und mit denen bei einem zugleich kompakten und einfachen Aufbau auf der Basis einer Korrelatortechnik eine zugleich orts- und zeitaufgeloste Messung der Intensitat ultrakurzer Laserimpulse im Einzelschusbetrieb erzielt wird, wird dadurch gelost, dass eine ortsaufgeloste nicht-kollineare Messung der Autokorrelationsfunktion erster oder hoherer Ordnung mittels einer Matrix aus strahlformenden Einzelelementen derart vorgenommen wird, dass eine ortliche Aufspaltung des Strahls in eine Strahl-Matrix aus konischen Teilstrahlen erfolgt, wobei jeder Teilstrahl die raumlich integrierte Information uber die von ihm durchstrahlte Teilflache der Matrix reprasentiert, die Ortsauflosung somit durch die Matrixgeometrie bestimmt wird und dass das durch jeden Teilstrahl in einer bestimmten, auf eine Matrixkamera abgebildeten Ebene im Raum erzeugte Interferenzmuster eine Autokorrelationsfunktion erster Ordnung oder unter Ausnutzung nicht-linearer Wechselwirkungen in einem geeigneten Medium entsprechend hoherer Ordnung liefert, so dass Koharenzzeit oder Impulsdauer von einzelnen Laserimpulsen oder Folgen mehrerer Laserimpulse als Funktion des Ortes bestimmt werden konnen.

Fiber based chirped pulse amplification system with 22 W average power [for laser plasma EUV generation]

Abstract: Summary form only given. We have demonstrated the potential of high-gain Yb-doped fiber amplifier systems to provide ultrashort pulses with average powers of 22 W, what is to our knowledge the highest level of fiber amplified pulses. 100 /spl mu/J pulses generated in a Yb-doped fiber with M/sup 2/ /spl ap/ 1.7 could be compressed to subpicosecond pulse duration. Compressed pulse durations are limited due to third order dispersion effects of the fiber stretcher-grating compressor setup. Nevertheless, the achievable intensities are high enough to create plasmas which can efficiently convert laser light to the EUV radiation.

Fiber based chirped pulse amplification system with 22 W average power

Abstract: For the generation of extreme ultraviolet (EUV) radiation from a laser plasma intensities of about 1012 W/cm2 to 1013 W/cm2 are needed.1

Compact diode-pumped microlaser with mode-selective thin film micro-mirrors

Abstract: Thin film micro-optics has been used for mode stabilization in a compact, diode-pumped Nd-doped solid-state laser. SiO2-microlenses and SiO2:HfO2-multilayer micro-mirrors have been tested in different resonator configurations starting from a hemispherical geometry. By comparing the stability behavior with the case of a macroscopic mirror it has been demonstrated that similar operation characteristics at a reduced output power can be achieved with a miniaturized laser. The special design of the thin film micro-optics can be used to enhance the mode-selectivity by spatial as well as spectral filtering with non-spherical phase distributions and profiled multilayer systems.

High Energy Ultrafast Fiber CPA System

Abstract: We report on a high-gain diode pumped ytterbium-doped fiber amplifier system delivering pulse energies in the 100 µJ range at high repetition rates (32 kHz) with nearly diffraction limited beam quality (M2 ≈ 1.7) at a 1060 nm center wavelength. Femtosecond seed laser pulses are stretched in a commercially available singlemode fiber and compressed after amplification to subpicosecond pulse duration. Power scaling up to several ml pulse energy, beam quality and limitations due to nonlinear effects using large-core-area and large-mode-area fibers will be discussed.

Process and arrangement for a space- and time-resolved interferometric characterization of ultrashort laser pulses

Abstract: The invention relates to methods and apparatus for temporally and spatially resolved characterization of ultrashort laser pulses. The object of the invention to develop generic method and an arrangement by which the described disadvantages of the prior art are avoided and with which at a same time compact and simple structure based on a Korrelatortechnik a both space- and time-resolved measurement of the intensity of ultrashort laser pulses is achieved in the single-shot operation, is achieved in that a spatially resolved non-collinear measuring the autocorrelation function of first or higher order is carried out by means of a matrix of beam shaping individual elements such that a local splitting of the jet takes place in a jet-matrix of the conical part beams, each partial beam spatially integrated information about the irradiated part of it surface of the matrix represents the spatial resolution is thus determined by the array geometry and that the e imaged by each partial beam in a particular, to a matrix camera bene generated interference pattern in space provides an autocorrelation function of the first order or by utilizing non-linear interactions in an appropriate medium corresponding to higher order so that coherence time or pulse duration can be determined by individual laser pulses or sequences of multiple laser pulses as a function of the place.

Spatial frequency effects of polychromatic ultrashort pulse Bessel beam arrays

Abstract: Summary form only given. Thin-film micro-optical components are interesting for ultrashort-pulse beam shaping and characterization because of specific advantages (low dispersion, compactness). Arrays allow to design spatially resolving autocorrelators. Recently, we demonstrated the generation of Bessel-beams from a Ti:sapphire laser for a pulse duration <30 fs in first experiments with arrays of Gaussian-shaped micro-axicons. Theoretical predictions concerning X-pulse formation by spectral interference of conical polychromatic wavepackets in THz and optical range could be verified by detecting characteristic changes of contrast. Whereas other groups used ring-shaped absorbing slits and lenses to transform small parts of the light into an optical Bessel beam, our scheme allows to transfer more energy into the interference zone and to shape a beam matrix by using refractive micro-axicon arrays. Beside the decreasing contrast with shorter pulses, spatial frequency changes were found. Blue-shift could be excluded as responsible mechanism. As a possible explanation, travel time effects were suggested which should be array-specific and neglectable for single elements. Here we give a detailed analysis of the problem of ultrashort pulse spatial frequency effects for arrays of Gaussian-shaped elements based on angular distribution and spectral bandwidth.