Self-referenced characterization of space-time couplings in near single-cycle laser pulses

We report on the characterization of space-time couplings in high energy sub-2-cycle 770nm laser pulses using a self-referencing single-shot method. Using spatially-encoded arrangement filter-based spectral phase interferometry for direct electric field reconstruction (SEA-F-SPIDER) we characterize few-cycle pulses with a wave-front rotation of 2.8x?10^11 rev/sec (1.38 mrad per half-cycle) and pulses with pulse front tilts ranging from to -0.33 fs/um to -3.03 fs/um.Comment: 6 pages, 6 figure

Attosecond sampling of arbitrary optical waveforms

Advances in the generation of ultrashort laser pulses, and the emergence of new research areas such as attosecond science, nanoplasmonics, coherent control, and multidimensional spectroscopy, have led to the need for a new class of ultrafast metrology that can measure the electric field of complex optical waveforms spanning the ultraviolet to the infrared. Important examples of such waveforms are those produced by spectral control of ultrabroad bandwidth pulses, or by Fourier synthesis. These are typically tailored for specific purposes, such as to increase the photon energy and flux of high-harmonic radiation, or to control dynamical processes by steering electron dynamics on subcycle time scales. These applications demand a knowledge of the full temporal evolution of the field. Conventional pulse measurement techniques that provide estimates of the relative temporal or spectral phase are unsuited to measure such waveforms. Here we experimentally demonstrate a new, all-optical method for directly measuring the electric field of arbitrary ultrafast optical waveforms. Our method is based on high-harmonic generation (HHG) driven by a field that is the collinear superposition of the waveform to be measured with a stronger probe laser pulse. As the delay between the pulses is varied, we show that the field of the unknown waveform is mapped to energy shifts in the high-harmonic spectrum, allowing a direct, accurate, and rapid retrieval of the electric field with subcycle temporal resolution at the location of the HHG

Attosecond streaking of photoelectron emission from disordered solids

Attosecond streaking of photoelectrons emitted by extreme ultraviolet light has begun to reveal how electrons behave during their transport within simple crystalline solids. Many sample types within nanoplasmonics, thin-film physics, and semiconductor physics, however, do not have a simple single crystal structure. The electron dynamics which underpin the optical response of plasmonic nanostructures and wide-bandgap semiconductors happen on an attosecond timescale. Measuring these dynamics using attosecond streaking will enable such systems to be specially tailored for applications in areas such as ultrafast opto-electronics. We show that streaking can be extended to this very general type of sample by presenting streaking measurements on an amorphous film of the wide-bandgap semiconductor tungsten trioxide, and on polycrystalline gold, a material that forms the basis of many nanoplasmonic devices. Our measurements reveal the near-field temporal structure at the sample surface, and photoelectron wavepacket temporal broadening consistent with a spread of electron transport times to the surface

Explosions of water clusters in intense laser fields

Energetic, highly-charged oxygen ions, $O^{q+}$ ($q\leq 6$), are copiously produced upon laser field-induced disassembly of highly-charged water clusters, $(H_2O)_n$ and $(D_2O)_n$, $n\sim$ 60, that are formed by seeding high-pressure helium or argon with water vapor. $Ar_n$ clusters (n$\sim$40000) formed under similar experimental conditions are found undergo disassembly in the Coulomb explosion regime, with the energies of $Ar^{q+}$ ions showing a $q^2$ dependence. Water clusters, which are argued to be considerably smaller in size, should also disassemble in the same regime, but the energies of fragment O$^{q+}$ ions are found to depend linearly on $q$ which, according to prevailing wisdom, ought to be a signature of hydrodynamic expansion that is expected of much larger clusters. The implication of these observations on our understanding of the two cluster explosion regimes, Coulomb explosion and hydrodynamic expansion, is discussed. Our results indicate that charge state dependences of ion energy do not constitute an unambiguous experimental signature of cluster explosion regime.Comment: Submitted to Phys. Rev.

Tax Principles, Policy Feedback and Self-Interest: Cross-National Experimental Evidence on Wealth Tax Preferences

Rising wealth inequality and squeezed public budgets has brought wealth tax back into policy discussions. A net wealth tax might help to boost state revenue and reduce wealth inequality. Yet little is known about citizens’ attitudes towards the design of a net wealth tax (i.e. the tax unit, exemption and rate). Using a novel multifactorial survey experiment, we examine citizens’ endorsement of fundamental principles of taxation. Building on policy feedback theory, we examine if preferences differ in three policy arenas (USA, Germany and UK) and whether individuals’ reasoning is dependent on self-interest. While a clear majority in all three countries generally endorses a wealth tax, our findings show that citizens care more about the amount exempted than the tax unit or rate. We do not identify a preference for any specific tax unit. Furthermore, tax preferences seem to be strikingly similar among citizens of all three countries. Yet we show that individuals are mostly concerned about not being personally affected by such a tax, which is reflected in their preference for substantial exemptions. We discuss our findings with regard to our understanding of wealth inequality, tax equity and the potential implications for policymakers.1. Introduction 2. Background 3. Data and method 4. Results 5. Discussion Footnotes Acknowledgements References Supplementary dat

Unequal but Just? Experimental Evidence on (Gendered) Distributive Justice Principles in Parental Financial Gifts

Research has documented gender inequalities in parental financial gifts, but it is unclear under which conditions these inequalities are socially accepted. We combine distributive justice theory with sociological and economic perspectives on intergenerational transfers to examine perceptions of fair allocations of parental gifts. By manipulating children’s characteristics in a multifactorial vignette experiment, we conducted in Germany in 2020 (N¼4284 observations of 714 respondents), we test the prevalence and gendered application of four justice principles (equality, need, entitlement and equity). While the equality principle was widespread, unequal gifts were legitimized both by children’s financial needs (unemployment) and exchange services (helping in parents’ household). These results indicate that the family is perceived as an agency for economic redistribution, potentially affecting society’s socio-economic structure. Moreover, exchange services weighed more for sons while needs weighed more for daughters, suggesting that gendered fairness perceptions are one possible mechanism explaining gender inequalities in financial gifts.1. Introduction 2. Theory and empirical background 3. Methods 4. Results 5. Discussion 6. Conclusion Acknowledgements References Supplementary dat

The Gender (Tax) Gap in Parental Transfers: Evidence from Administrative Inheritance and Gift Tax Data

This study examines how inheritance and gift tax systems in combination with gendered parental transfer behavior strengthen gender wealth inequalities. Gender differences in transfers can be reproduced if men benefit differently than women from tax exemptions. This might happen when men and women receive different types of assets where only some are tax-exempted. To investigate gendered parental transfer behavior and gender differences in tax rates, we draw on German administrative inheritance and gift tax data. Women were less likely than men to receive tax-relevant parental transfers, the value of the transfers were lower, and women and men differed in the asset types they received. Moreover, we identify a gender tax gap of 2% for inheritances and 22% for gifts. Our analyses suggest that men benefit more from tax exemptions on business assets. This study adds the tax system as yet another factor implicated in the reproduction of gender wealth inequalities. (Stone Center on Socio-Economic Inequality Working Paper