Introduction to the Special Issue on Structured Light Coherence

Statistical optics, and optical coherence in particular, developed into a stand-alone branch of physical optics in the second half of the 20th century and has found a number of ground-breaking applications in astronomical measurements, medical diagnostics, environmental remote sensing, and wireless communications [...]

Constraint analysis of measurement accuracy in high-precision X-ray pulsar positioning

In this paper, the relationship between direct measurement of X-ray pulsar angular position and second-order correlation is analyzed by classical statistical optics. On this basis, a scheme for measuring pulsar angle position is put forward on account of X-ray band intensity correlation, which is expected to achieve a positioning accuracy of 10 Mas. Finally, the connection between positioning accuracy and complex correlation in the intensity correlation measurement is studied. Also, main factors that affected the measurement are analyzed.

Numerical analysis of brilliance and coherent photon flux of segmented undulator radiation based on statistical optics

A method based on wave optics together with electron tracking is used to analyze synchrotron radiation from a segmented undulator in a double or multi mini-β function lattice storage ring. Radiation brilliance and transverse coherence features are investigated, where the former is calculated with the Wigner distribution function and the latter is evaluated by integrating the photon flux and cross-spectral density to exhibit the coherent flux and overall degree of coherence. To be specific, radiation properties for a single undulator in a typically single mini-β function and a tandem undulator in a double mini-β y lattice are compared in this work. As a result, both, brilliance and coherent flux can be enhanced by a second tandem undulator at the Taiwan Photon Source.

ANALYSIS OF A TWO-CRYSTAL DELAY LINE FOR FEMTOSECOND PULSES OF THE X-RAY FREE ELECTRON LASER

Using the methods of statistical optics the formation of delayed X-ray pulses in the diffraction reflection of an incident pulse with an arbitrary degree of temporal coherence from a system of parallel crystals with different lattice periods is considered. The results are of interest for constructing delay lines in experiments with a time resolution of the pump-and-probe type and realizing of the self-seeding mode to increase the degree of temporal coherence of the X-ray free-electron laser radiation. A rigorous theory of dynamic diffraction in Bragg geometry is applied to the diffraction reflection of short X-ray pulses from a system of two parallel crystals with arbitrary thicknesses, and also, for a system of two pairs of parallel crystals. The dependence of the delay time and the intensity of the delayed pulses on the thickness of the crystals and the distances between them are analyzed. Since the pulses from the X-ray free electron laser have high spatial coherence, i.e. a small angular divergence, but very poor temporal coherence, special attention is paid to the effect of the degree of temporal coherence on the width of the energy spectrum of the incident pulses and on the influence of this width on the intensity of the delayed pulses.