Advisors

Nano optics: Ultrashort pulse-induced nanogratings

When ultrashort laser pulses are focused into transparent materials nonlinear absorption leads to localized energy deposition in the focal volume [1]. In glasses self-organized periodic sub-wavelength structures, so-called nanogratings, emerge in a certain parameter regime resulting in birefringent modifications embedded within the otherwise isotropic host material [2]. The nanogratings evolve under the irradiation of several hundred laser pulses and are always oriented perpendicular to the laser polarization (see figure). Hence their structural properties and thus their birefringence can be controlled by tuning the laser parameters [3]. Within this project the formation process and the influence of different processing parameters is investigated. Based on this analysis different optical elements for the local control of the polarization, ranging from waveplates e.g. for the generation of radial or azimuthal polarization to complex structures for advanced microscopy techniques or even chiral structures will be realized.

References

  1. K. Itoh, W. Watanabe, S. Nolte, C. Schaffer, “Ultrafast processes for bulk modification of transparent materials,” MRS Bull. 31, 620-625 (2006).
  2. S. Richter, A. Plech, M. Steinert, M. Heinrich, S. Döring, F. Zimmermann, U. Peschel, E.- B. Kley, A. Tünnermann, and S. Nolte, “On the fundamental structure of femtosecond laser-induced nanogratings,“ Laser Photonics Rev. 6, 787-792 (2012).
  3. L.P.R. Ramirez, M. Heinrich, S. Richter, et al.,“Tuning the structural properties of femtosecond-laser induced nanogratings,” Appl. Phys. A 100, 1-6 (2010).

Fig: a) Sketch of the nanograting inscribing process. b) Development of nanogratings with increasing number of laser pulses incident. c) Three-dimensional reconstruction of the fundamental structure of femtosecond pulse-induced nanostructures.

Contact:

Felix.Zimmermann@uni-jena.de