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Quantum path interferences occur whenever multiple equivalent and coherent transitions result in a common final state. Such interferences strongly modify the probability of a particle to be found in that final state, a key concept of quantum coherent control. When multiple nonlinear and energy-degenerate transitions occur in a system, the multitude of possible quantum path interferences is hard to disentangle experimentally. Here, we analyze quantum path interferences during the nonlinear emission of electrons from hybrid plasmonic and photonic fields using time-resolved photoemission electron microscopy. We experimentally distinguish quantum path interferences by exploiting the momentum difference between photons and plasmons and through balancing the relative contributions of their respective fields. Our work provides a fundamental understanding of the nonlinear photon–plasmon–electron interaction. Distinguishing emission processes in momentum space, as introduced here, could allow nano-optical quantum-correlations to be studied without destroying the quantum path interferences.

The optical and electronic tunability of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has enabled emerging applications as diverse as bioelectronics, flexible electronics, and micro- and nano-photonics. High-resolution spatial patterning of PEDOT:PSS opens up opportunities for novel active devices in a range of fields. However, typical lithographic processes require tedious indirect patterning and dry etch processes, while solution-processing methods such as ink-jet printing have limited spatial resolution. Here, we report a method for direct write nano-patterning of commercially available PEDOT:PSS through electron-beam induced solubility modulation. The written structures are water stable and maintain the conductivity as well as electrochemical and optical properties of PEDOT:PSS, highlighting the broad utility of our method. We demonstrate the potential of our strategy by preparing prototypical nano-wire structures with feature sizes down to 250 nm, an order of magnitude finer than previously reported direct write methods, opening the possibility of writing chip-scale microelectronic and optical devices. We finally use the high-resolution writing capabilities to fabricate electrically-switchable optical diffraction gratings. We show active switching in this archetypal system with >95 % contrast at CMOS-compatible voltages of +2 V and −3 V, offering a route towards highly-miniaturized dynamic optoelectronic devices.

The spectral relaxation of photogenerated excitations and the stimulated emission is studied in an alpha-sexithienyl single crystal using femtosecond differential transmission spectroscopy and time-resolved photoluminescence measurements at low temperature. Stimulated emission with amplification of the probe light which results in a positive differential transmission signal is found at two spectral positions for polarization parallel to the molecular c-axis.

Author(s): Th. Weber [1]; H. Giessen [2]; M. Weckenbrock [1]; G. Urbasch [2]; A. Staudte [1]; L. Spielberger [1]; O. Jagutzki [1]; V. Mergel [1]; M. Vollmer [2]; R. Dörner [...]

A universal approach to increase the bandwidth of the widely used shear-force feedback using lock-in technique is presented. It was observed that a good bandwidth is not attained by optimizing the phase offset of the lock-in for signal amplitude alone. A theoretical model that discloses the relation between the mechanical and electrical properties of the combination of tuning fork and fiber tip is developed. Using a numerical simulation based on the model, the frequency response of the shear-force detection system is measured.