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G. W. 't Hooft

Publications and source records attributed to G. W. 't Hooft.

6 recordsLinked to original sources
arXiv2015

Light is Heavy

Einstein's relativity theory appears to be very accurate, but at times equally puzzling. On the one hand, electromagnetic radiation must have zero rest mass in order to propagate at the speed of light, but on the other hand, since it definitely carries momentum and energy, it has non-zero inertial mass. Hence, by the principle of equivalence, it must have non-zero gravitational mass, and so, light must be heavy. In this paper, no new results will be derived, but a possibly surprising perspective on the above paradox is given.

physics.hist-ph↗
arXiv2008

Shannon dimensionality of quantum channels and its application to photon entanglement

We introduce the concept of Shannon dimensionality D as a new way to quantify bipartite entanglement as measured in an experiment. This is applied to orbital-angular-momentum entanglement of two photons, using two state analyzers composed of a rotatable angular-sector phase plate that is lens-coupled to a single-mode fiber. We can deduce the value of D directly from the observed two-photon coincidence fringe. In our experiment, D varies between 2 and 6, depending on the experimental conditions. We predict how the Shannon dimensionality evolves when the number of angular sectors imprinted in the phase plate is increased and anticipate that D = 50 is experimentally within reach.

quant-ph↗
arXiv2007

Observation of Goos-Hänchen shifts in metallic reflection

We report the first observation of the Goos-H$\rm \ddot{\textbf{a}}$nchen shift of a light beam incident on a metal surface. This phenomenon is particularly interesting because the Goos-H$\rm \ddot{\textbf{a}}$nchen shift for $p$ polarized light in metals is negative and much bigger than the positive shift for $s$ polarized light. The experimental result for the measured shifts as a function of the angle of incidence is in excellent agreement with theoretical predictions. In an energy-flux interpretation, our measurement shows the existence of a backward energy flow at the bare metal surface when this is excited by a $p$ polarized beam of light.

physics.optics↗
arXiv2004

Photoluminescence studies study of a phenyl-substituted PPV

We report on the photophysics of a phenyl-substituted PPV both in solution and as a film. For both systems we have studied the decay of the photoluminescence and of the emission anisotropy for a large set of wavelengths spanning the entire photoluminescence spectrum. At long wavelengths the decay behavior is that of an interchain species. At the shortest wavelengths the decay of the photoluminescence from the film is observed to have a long-lived component, in addition to the rapidly decaying component usually associated with energy transfer. We attribute this slow component to emission by isolated intrachain excitons with reduced nonradiative relaxation.

physics.chem-ph↗
arXiv2004

Measuring the gain dynamics in a conjugated polymer film

We present a simple method for measuring the gain decay time in a conjugated polymer film by optically exciting the film with two mutually delayed ultrashort pump pulses. When the pump is set at such a power level that amplified spontaneous emission marginally develops along the polymer waveguide, the total output emitted from its edge decays exponentially as a function of the interpulse delay. The corresponding decay time represents the decay time of the gain of the polymer material.

physics.chem-ph↗