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Simultaneously spatially and temporally focusing light for tailored ultrafast micro-machining

: Thomas, Jens U.; Block, Erica; Greco, Michael; Meier, Amanda; Durfee, Charles G.; Squier, Jeffrey A.; Nolte, Stefan; Tünnermann, Andreas


Heisterkamp, A. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Frontiers in Ultrafast Optics. Biomedical, Scientific, and Industrial Applications XIV : February 2014, San Francisco, California, United States
Bellingham, WA: SPIE, 2014 (SPIE Proceedings 8972)
ISBN: 978-0-8194-9885-4
Paper 897219
Conference "Frontiers in Ultrafast Optics - Biomedical, Scientific, and Industrial Applications" <14, 2014, San Francisco/Calif.>
Fraunhofer IOF ()
ultrafast optics; micromachining; dispersion; focussing; wave optics

Simultaneous spatially and temporally focussing (SSTF) of ultrashort pulses allows for an unprecedented control of the intensity distribution of light. It has therefore a great potential for widespread applications ranging from nonlinear microscopy, ophthalmology to micro-machining. SSTF also allows to overcome many bottlenecks of ultrashort pulse micro-machining, especially non-linear effects like filamentation and self-focussing. Here, we describe and demonstrate in detail how SSTF offers an additional degree of freedom for shaping the focal volume. In order to obtain a SSTF beam, the output of an ultrafast laser is usually split by a grating into an array of copies of the original beam, which we refer to as beamlets. The ratio of the beamlet array width to the width of the invidual beamlet is the beam aspect ratio. The focal volume of the SSTF beam can now be tailored transversally by shaping the cross-section of the beamlets and axially by choosing the right beam aspect ratio. We will discuss the requirements of the setup for a successful implementation of this approach: Firstly, the group velocity dispersion and the third order dispersion have to be compensated in order to obtain a high axial confinement. Secondly, the beamlet size and their orientation should not vary too much spectrally. Thirdly, beamlet and SSTF focus should match. We will hence demonstrate how SSTF allows to inscribe tailored three-dimensional structures with fine control over their aspect ratio. We also show how the SSTF focus can be adapted for various glasses and crystals.