We show the real-space observation of fast and slow pulses propagating inside a photonic crystal waveguide by time-resolved near-field scanning optical microscopy. Local phase and group velocities of modes are measured. For a specific optical frequency we observe a localized pattern associated with a flat band in the dispersion diagram. 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.
Expect the unexpected: The interaction between cyanuric acid (CA) and melamine (M) molecules is a key structural motif in supramolecular chemistry. The adsorption and coadsorption of M and CA on a Au(111) surface under ultrahigh vacuum (UHV) is investigated using STM with submolecular resolution (see image). In addition to the expected structure with a 1:1 CA/M ratio, a novel phase with a 1:3 CA/M forms upon sequential deposition.
We present the first experimental proof for the influence of a nearby nanosized metal object on the angular photon emission by a single molecule. Using a novel angular sensitive detection scheme, we directly quantify the redirection of angular emission for different molecular dipole orientations as an object is scanned laterally over the molecule at different heights. An excellent agreement between experiments and 2D-numerical simulations is found for molecules oriented perpendicular to the sample, whereas, for parallel orientations, the observed behavior contradicts the calculated behavior.
We show that the propagation of a femtosecond laser pulse inside a photonic structure can be directly visualized and tracked as it propagates using a time-resolved photon scanning tunneling microscope. From the time-dependent and phase-sensitive measurements, both the group velocity and the phase velocity are unambiguously and simultaneously determined. It is expected that this technique will find applications in the investigation of the local dynamic behavior of photonic crystals and integrated optical circuits.
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