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- ItemGeneration of millijoule few-cycle pulses at 5 μm by indirect spectral shaping of the idler in an optical parametric chirped pulse amplifier(Washington, DC : Soc., 2018) Bock, Martin; Grafenstein, Lorenz von; Griebner, Uwe; Elsaesser, ThomasSpectral pulse shaping in a high-intensity midwave-infrared (MWIR) optical parametric chirped pulse amplifier (OPCPA) operating at 1 kHz repetition rate is reported. We successfully apply a MWIR spatial light modulator (SLM) for the generation of ultrashort idler pulses at 5 μm wavelength. Only bulk optics and active phase control of the 3.5 μm signal pulses via the SLM are employed for generating compressed idler pulses with a duration of 80 fs. The 80-fs pulse duration corresponds to less than five optical cycles at the central wavelength of 5.0 μm. The pulse energy amounts to 1.0 mJ, which translates into a peak power of 10 GW. The generated pulse parameters represent record values for high-intensity MWIR OPCPAs.
- Item43 W, 1.55 μm and 12.5 W, 3.1 μm dual-beam, sub-10 cycle, 100 kHz optical parametric chirped pulse amplifier(Washington, DC : Soc., 2018) Mero, Mark; Heiner, Zsuzsanna; Petrov, Valentin; Rottke, Horst; Branchi, Federico; Thomas, Gabrielle M.; Vrakking, Marc J. J.We present a 100 kHz optical parametric chirped pulse amplifier (OPCPA) developed for strong-field attosecond physics and soft-x-ray transient absorption experiments. The system relies on noncollinear potassium titanyl arsenate booster OPCPAs and is pumped by a 244 W, 1.1 ps Yb:YAG Innoslab chirped pulse laser amplifier. Two optically synchronized infrared output beams are simultaneously available: a 430 μJ, 51 fs, carrier-envelope phase stable beam at 1.55 μm and an angular-dispersion-compensated, 125 μJ, 73 fs beam at 3.1 μm.
- ItemTowards Poisson noise limited optical pump soft X-ray probe NEXAFS spectroscopy using a laser-produced plasma source(Washington, DC : Soc., 2019) Jonas, Adrian; Stiel, Holger; Glöggler, Lisa; Dahm, Diana; Dammer, Katharina; Kanngießer, Birgit; Mantouvalou, IoannaWe present a laboratory setup for near edge X-ray absorption spectroscopy (NEXAFS) in the soft X-ray regime between 284 eV to 1303 eV with a resolving power of up to 1370. Based on a laser-produced plasma source, a pair of identical reflection zone plates and an X-ray CCD camera, the setup is intended for optical pump X-ray probe NEXAFS measurements with a detectable change in absorption of the excited sample down to 10-4 and 500 ps time resolution. Because of the high stability of the source the statistical error only depends on the detector response and the number of photons detected and can reach the detector noise limit after a couple of thousands single shots. Thus, structure-function relationship investigations of bio-molecules are rendered feasible in the laboratory.
- ItemConvective Nozaki-Bekki holes in a long cavity OCT laser(Washington, DC : Soc., 2019) Slepneva, Svetlana; O'Shaughnessy, Ben; Vladimirov, Andrei G.; Rica, Sergio; Viktorov, Evgeny A.; Huyet, GuillaumeWe show, both experimentally and theoretically, that the loss of coherence of a long cavity optical coherence tomography (OCT) laser can be described as a transition from laminar to turbulent flows. We demonstrate that in this strongly dissipative system, the transition happens either via an absolute or a convective instability depending on the laser parameters. In the latter case, the transition occurs via formation of localised structures in the laminar regime, which trigger the formation of growing and drifting puffs of turbulence. Experimentally, we demonstrate that these turbulent bursts are seeded by appearance of Nozaki-Bekki holes, characterised by the zero field amplitude and π phase jumps. Our experimental results are supported with numerical simulations based on the delay differential equations model.
- ItemDifferential Cross Sections for the H + D2 → HD(v′ = 3, j′ = 4-10) + D Reaction above the Conical Intersection(Washington, DC : Soc., 2015) Gao, Hong; Sneha, Mahima; Bouakline, Foudhil; Althorpe, Stuart C.; Zare, Richard N.We report rovibrationally selected differential cross sections (DCSs) of the benchmark reaction H + D2 → HD(v′ = 3, j′ = 4–10) + D at a collision energy of 3.26 eV, which exceeds the conical intersection of the H3 potential energy surface at 2.74 eV. We use the PHOTOLOC technique in which a fluorine excimer laser at 157.64 nm photodissociates hydrogen bromide (HBr) molecules to generate fast H atoms and the HD product is detected in a state-specific manner by resonance-enhanced multiphoton ionization. Fully converged quantum wave packet calculations were performed for this reaction at this high collision energy without inclusion of the geometric phase (GP) effect, which takes into account coupling to the first excited state of the H3 potential energy surface. Multimodal structures can be observed in most of the DCSs up to j′ = 10, which is predicted by theory and also well-reproduced by experiment. The theoretically calculated DCSs are in good overall agreement with the experimental measurements, which indicates that the GP effect is not large enough that its existence can be verified experimentally at this collision energy.
- ItemTropospheric Aqueous-Phase Oxidation of Isoprene-Derived Dihydroxycarbonyl Compounds(Washington, DC : Soc., 2017) Otto, Tobias; Stieger, Bastian; Mettke, Peter; Herrmann, HartmutThe dihydroxycarbonyls 3,4-dihydroxy-2-butanone (DHBO) and 2,3-dihydroxy-2-methylpropanal (DHMP) formed from isoprene oxidation products in the atmospheric gas phase under low-NO conditions can be expected to form aqSOA in the tropospheric aqueous phase because of their solubility. In the present study, DHBO and DHMP were investigated concerning their radical-driven aqueous-phase oxidation reaction kinetics. For DHBO and DHMP the following rate constants at 298 K are reported: k(OH + DHBO) = (1.0 ± 0.1) × 109 L mol-1 s-1, k(NO3 + DHBO) = (2.6 ± 1.6) × 106 L mol-1 s-1, k(SO4-+ DHBO) = (2.3 ± 0.2) × 107 L mol-1 s-1, k(OH + DHMP) = (1.2 ± 0.1) × 109 L mol-1 s-1, k (NO3 + DHMP) = (7.9 ± 0.7) × 106 L mol-1 s-1, k(SO4- + DHMP) = (3.3 ± 0.2) × 107 L mol-1 s-1, together with their respective temperature dependences. The product studies of both DHBO and DHMP revealed hydroxydicarbonyls, short chain carbonyls, and carboxylic acids, such as hydroxyacetone, methylglyoxal, and lactic and pyruvic acid as oxidation products with single yields up to 25%. The achieved carbon balance was 75% for DHBO and 67% for DHMP. An aqueous-phase oxidation scheme for both DHBO and DHMP was developed on the basis of the experimental findings to show their potential to contribute to the aqSOA formation. It can be expected that the main contribution to aqSOA occurs via acid formation while other short-chain oxidation products are expected to back-partition into the gas phase to undergo further oxidation there.
- ItemActive Plasmonic Colloid-to-Film-Coupled Cavities for Tailored Light-Matter Interactions(Washington, DC : Soc., 2019) Goßler, Fabian R.; Steiner, Anja Maria; Stroyuk, Oleksandr; Raevskaya, Alexandra; König, Tobias A.F.For large-scale fabrication of optical circuits, tailored subwavelength structures are required to modulate the refractive index. Here, we introduce a colloid-to-film-coupled nanocavity whose refractive index can be tailored by various materials, shapes, and cavity volumes. With this colloidal nanocavity setup, the refractive index can be adjusted over a wide visible wavelength range. For many nanophotonic applications, specific values for the extinction coefficient are crucial to achieve optical loss and gain. We employed bottom-up self-assembly techniques to sandwich optically active ternary metal-chalcogenides between a metallic mirror and plasmonic colloids. The spectral overlap between the cavity resonance and the broadband emitter makes it possible to study the tunable radiative properties statistically. For flat cavity geometries of silver nanocubes with sub-10 nm metallic gap, we found a fluorescence enhancement factor beyond 1000 for 100 cavities and a 112 meV Rabi splitting. In addition, we used gold spheres to extend the refractive index range. By this easily scalable colloidal nanocavity setup, gain and loss building blocks are now available, thereby leading to new generation of optical devices. Copyright © 2019 American Chemical Society.