The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications.
We report the experimental observation of all-optical modulation of light in a graphene film. The graphene film is scanned across a standing wave formed by two counter-propagating laser beams in a Sagnac interferometer. Through a coherent absorption process the on-axis transmission is modulated with close to 80% efficiency. Furthermore we observe modulation of the scattered energy by mapping the off-axis scattered optical signal: scattering is minimized at a node of the standing wave pattern and maximized at an antinode. The results highlight the possibility to switch and modulate any given optical interaction with deeply sub-wavelength films. PACS numbers: 310.6860, 310.6628, 240.3695, 310.1030 Sub-wavelength media, such as metamaterials, graphene and heterostructure layered media [1][2][3], have great potential to provide enhanced functionality to optomechanical and photonic devices. A major limitation in the use of these materials is inefficient light-matter coupling at the nanoscale.Here, we examine the possibility to control both the absorption and scattering of light from graphene films through a process related to 'coherent perfect absorption' (CPA).Coherent perfect absorption was first proposed in thick absorbing media, i.e., thicker than the optical wavelength [4, 5], whereby the medium acts as a resonator cavity. Through a mechanism similar to a time-reversed laser [6, 7], two coherent, monochromatic counterpropagating beams will be perfectly absorbed. These processes have been further developed in alternative geometries [8, 9], including coherent absorption in nonlinear media [10].It has recently been shown that it is also possible to observe CPA in a sub-wavelength film, allowing the coherent modulation of 'light-with-light' without the use of nonlinearity [11][12][13]. This is possible due to the intricate nature of light-matter interaction at the nanoscale. Coherent light-with-light modulation in sub-wavelength films may arise in the presence of two counter-propagating light beams, a and b, that form a standing wave (within the coherence length of the laser). A sub-wavelength film that is placed in the path of the counter-propagating beams experiences a very different electric field amplitude, depending on its position within the standing wave. If the film is positioned within a node of the standing wave, the electric field amplitude is constant in time and equal to zero: the light beams will pass the film without loss. However at an anti-node, the position of maximum amplitude of the field, the light beams undergo strong, ideally 100% absorption. This provides a method to modulate the absorption of light with a thin absorbing film by simply changing the relative phases of the interacting beams. This mechanism was first reported using a metamaterial thin film structure with properties tuned so as to provide a * Corresponding author: d.faccio@hw.ac.uk single-pass absorption close to the ideal 50% limit that is required for perfect 100% coherent absorption [11, 14]. In single layer graphene, simil...
Time t (ps) 3.1 eV 4.1 meV ×2.7 Joint fit 1/Γ ee =100 fs
SUMMARY Short-term i.v. infusion of streptokinase was performed in 93 patients within 6 hours after the onset of acute myocardial infarction. Twenty-six patients underwent angiography in the acute phase (group A) and 52 underwent angiography in the fourth week only (group B); 15 patients had no angiography. Seven patients died during the hospital stay and six suffered nonfatal reinfarctions. There were no bleeding complications.In 11 of 21 group A patients, occluded coronary arteries were opened within 1 hour after the streptokinase infusion was started. In 84% of groups A and B, the infarct-related coronary artery was patent in the fourth week. In 75% of the patent arteries, the residual luminal diameter stenosis was less than 70%. According to serial serum CK-MB curves, recanalization was achieved mostly within 1-2 hours.Myocardial salvage was indicated by improvement in local contraction disorders in the recanalized group A patients and by the significant relationship between infarct size and time from symptom onset to treatment in group B.These data suggest that a high-dose, short-term, i.v. infusion of streptokinase is a safe and efficient method of restoring coronary blood flow. Expeditious initiation of i.v. streptokinase infusion is a critical determinant for early recanalization and salvage of myocardium. Patients with thrombotically subtotal occlusion probably receive the most benefit. Evaluation of the true impact on survival and myocardial function will require controlled clinical trials. THE MOST effective way to limit myocardial necrosis in evolving myocardial infarction may be early restoration of coronary blood flow. This concept is based on animal studies demonstrating that early revascularization can reduce the predicted extent of myocardial infarction'" and can favorably affect survival.5Coronary angiography within a few hours after transmural myocardial infarction in man has revealed a high incidence of coronary arteries occluded by thrombus.6' 7 This finding is in accordance with the postmortem findings of occlusive thrombi in about 90% of patients dying of acute transmural myocardial infarction.>" These findings were the rationale for intracoronary thrombolysis as a method of coronary artery reperfusion in patients with evolving myocardial infarction. In recent clinical studies, early reopening of the thrombotically occluded coronary artery could be demonstrated in most patients with acute myocardial infarction.4 12-14 The aim of our study was to evaluate whether i.v. streptokinase in a high-dose, short-term infusion could produce similar results. Preliminary data have already been presented. '5' 16 After the procedure was explained, each patient gave informed consent. The Ethical Committee of the Berlin Free University Steglitz hospital approved the study. Methods Patients and TreatmentNinety-three patients with symptoms and an ECG typical of acute myocardial infarction were selected for the study. Patients with contraindications to thrombolysis and anticoagulation and those in whom tre...
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