IN THIS SECTION
ORC Seminar Series
"Time resolved motion of pulses in photonic crystal waveguides: a real space investigation "
Speaker: H. Gersen
Date: 4 February 2009
Venue: B53 Seminar Room
H. Gersen1,*, T.J. Karle2, J. P. Korterik1, T.F. Krauss2, N.F. van Hulst1, L Kuipers1,3
1) Applied Optics group, MESA+ Research Institute, University of Twente, NL.
2) Photonic Band Gap Research Group, University of St. Andrews, UK.
3) Nanophotonics Group, FOM-institute for Atomic and Molecular Physics (AMOLF), NL.
*) Currently part of : Nano-physics and Soft Matter Group, University of Bristol, UK
Strong dispersion combined with distributed Bragg diffraction makes pulse propagation through a photonic crystal (PhC) an exciting research topic. To study the complex interplay between different mechanisms, local time-resolved measurements are crucial. However, peeking inside a photonic structure is far from trivial as conventional optical microscopy is limited by the diffraction limit. What occurs inside the device therefore remains mostly hidden. Recently, we demonstrated a non-invasive technique to “visualize” pulses as they propagate through an optical device with both temporal and spatial resolution. [1,2]
Figure 1 schematically depicts how we extended a heterodyne detection phase-sensitive PSTM, which allows the measurement of both the amplitude and phase of propagating light , to perform local time-resolved measurements. At a reference time determined by the position of an optical delay the position of a pulse is pinpointed. With this technique we have recently been able to observe time-resolved motion of an ultrashort pulse through a photonic crystal waveguide. Figure 2 shows an example for a fixed reference time in which a 120 femtosecond pulse has split in multiple pulses each with a different modal distribution. By repeating this measurement for different reference times the motion of each pulse can be followed through the waveguide in time, giving a direct measure for local group and phase velocities. At the same time the phase-sensitivity of our technique allows to directly measure the bandstructure for the first time, revealing multiple Brillouin zones due to zone folding. At a specific optical frequency the existence of long-lived modes not propagating along the waveguide is found. During at least 3 ps, movement of this field is hardly discernible: its group velocity would be at most c/1000. The huge trapping times without the use of a cavity reveal new perspectives for dispersion and time control within photonic crystals.
 M.L.M. Balistreri, H. Gersen, J.P. Korterik et al., Science 294 (5544), 1080 (2001).
 H. Gersen, J.P. Korterik, N.F. van Hulst, and L. Kuipers, Phys. Rev. E. 68, 026604-1 (2003).
 M.L.M. Balistreri, J.P. Korterik, L. Kuipers et al., Phys. Rev. Lett. 85, 294 (2000).
 H. Gersen, et. al., Phys. Rev. Lett. 94, 123901 (Apr. 2005)
 H. Gersen, et. al., Phys. Rev. Lett. 94, 073903 (Feb. 2005)
Copyright University of Southampton 2006