Seminar: "Large-scale grain-boundary-free copper films for nanoplasmonics" & "Single-shot intensity-corrected phase tagging for weak carrier-envelope-phase effects" by Dr. Soo Hoon Chew

1. Large-scale grain-boundary-free copper films for nanoplasmonics
Copper is generally regarded as a poor plasmonic material compared to gold and silver because of its notorious oxidation issues when subjected to air exposure. Here, I will discuss the use of large-scale grain-boundary-free copper films grown epitaxially on sapphire substrates in combination with focused ion beam milling to pattern plasmonic nanostructures with superior quality. The copper films prepared using a single-crystal copper sputtering target exhibit a strong resistance to oxidation, overcoming the bottleneck in conventional copper film fabrication. Hence, copper surfaces with a very low roughness, high conductivity and high durability can be achieved. The atomically flat single-crystal copper films yield improved optical properties and enhanced robustness, confirmed by surface plasmon resonance and extraordinary optical transmission measurements.

2. Single-shot intensity-corrected phase tagging for weak carrier-envelope-phase effects
The presence of a laser intensity-related carrier-envelope-phase (CEP) artefact in CEP-dependent nonlinear photoemission experiments using a single-shot CEP tagging technique has obscured the detection of weak intrinsic CEP effects. The artefact is found to be correlated with random laser intensity fluctuations in the experimental setup. This issue is remedied by implementing single-shot intensity tagging in addition to the present CEP tagging technique in order to assign a corresponding laser intensity to each detected photoelectron for every laser shot. After applying intensity filtering and an appropriate intensity correction, we demonstrate the capability of detecting weakly CEP-dependent photoemission from a bulk tungsten surface with a modulation depth as low as ~1% within a measurement time of ~30 min at 10 kHz repetition rate. Our approach has proven successful in increasing the sensitivity of the single-shot CEP tagging technique, which allows the studies of weak CEP effects in atoms, molecules and solids.

Bio: Soo Hoon Chew received her Master of science in physics from University of Malaya, Malaysia, and Ph.D. in physics from Ludwig Maximilian University of Munich, Germany. Since 2016, she joined Max Planck POSTECH/KOREA Research Initiative as a reseacher and she is currently working in Pusan National Unversity, South Korea. Her main research interests include attosecond imaging using extreme ultraviolet pulses from high harmonic generation and carrier-envelope-phase control of plasmonic nanostructures and metal surfaces, femtosecond time-resolved photoemission electron microscopy for studying plasmonic materials as well as plasmonic applications using optical characterization techniques.