University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Control reconfiguration & Software. The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

Rotational Doppler effect in nonlinear optics

Abstract: The change in pitch of a passing car engine is a classic example of the translational Doppler effect, but rotational Doppler shifts can also arise, as shown for circularly polarized light passing through a spinning nonlinear optical crystal. The translational Doppler effect of electromagnetic and sound waves has been successfully applied in measurements of the speed and direction of vehicles, astronomical objects and blood flow in human bodies1,2,3,4,5,6,7,8, and for the Global Positioning System. The Doppler effect plays a key role for some important quantum phenomena such as the broadened emission spectra of atoms9 and has benefited cooling and trapping of atoms with laser light10,11,12. Despite numerous successful applications of the translational Doppler effect, it fails to measure the rotation frequency of a spinning object when the probing wave propagates along its rotation axis. This constraint was circumvented by deploying the angular momentum of electromagnetic waves13—the so-called rotational Doppler effect. Here, we report on the demonstration of rotational Doppler shift in nonlinear optics. The Doppler frequency shift is determined for the second harmonic generation of a circularly polarized beam passing through a spinning nonlinear optical crystal with three-fold rotational symmetry. We find that the second harmonic generation signal with circular polarization opposite to that of the fundamental beam experiences a Doppler shift of three times the rotation frequency of the optical crystal. This demonstration is of fundamental significance in nonlinear optics, as it provides us with insight into the interaction of light with moving media in the nonlinear optical regime.

Procrastination in Different Life-Domains: Is Procrastination Domain Specific?

Abstract: Procrastination, putting off until tomorrow what one had intended to do today, is a well-known phenomenon in everyday life. In an attempt to understand the character of procrastination, a large body of research has been accumulating over the last 40 years. The present study was to evaluate the need to distinguish between procrastination in different life-domains by gathering first hints as to whether procrastination is domain specific or domain general. In an online survey on 260 students (mean age = 23.56; SD = 3.74) the procrastination frequency in 6 different life-domains (academic and work, everyday routines and obligations, health, leisure, family and partnership, social contacts) was examined. Confirmatory factor analysis (CFA) and the analysis of mean-level differences revealed that procrastination is domain specific, but not extremely so. The results encourage further investigations into the domain specificity of procrastination and suggest that future diagnoses of and interventions for procrastination will profit from considering the life-domain procrastination occurs in.