RESUMO
Diffractive lenses are popular in large optical systems owing to their lightweight and multifunctional design. However, they are difficult to calibrate accurately due to the cross talk between the first-order diffraction and the background light. Here, a quadriwave lateral shearing interferometry (QWLSI) with spherical wave illumination was proposed to absolutely measure the focusing properties of diffractive lenses by means of the reference background light, in which the corresponding theoretical modeling was first derived, and then the single-shot experiment on a 210 mm-diameter beam was carried out. The results showed that the measurement error of the focal length was 0.59%, and the consistency error was 0.008%.
RESUMO
We report a new scenario of the time-of-flight technique in which fast neutrons and delayed gamma-ray signals were both recorded in a millisecond time window in harsh environments induced by high-intensity lasers. The delayed gamma signals, arriving far later than the original fast neutron and often being ignored previously, were identified to be the results of radiative captures of thermalized neutrons. The linear correlation between the gamma photon number and the fast neutron yield shows that these delayed gamma events can be employed for neutron diagnosis. This method can reduce the detecting efficiency dropping problem caused by prompt high-flux gamma radiation and provides a new way for neutron diagnosing in high-intensity laser-target interaction experiments.
RESUMO
The adaptive optics system for the second-generation VLT-interferometer (VLTI) instrument GRAVITY consists of a novel cryogenic near-infrared wavefront sensor to be installed at each of the four unit telescopes of the Very Large Telescope (VLT). Feeding the GRAVITY wavefront sensor with light in the 1.4 to 2.4 micrometer band, while suppressing laser light originating from the GRAVITY metrology system, custom-built optical components are required. In this paper, we present the development of a quantitative near-infrared point diffraction interferometric characterization technique, which allows measuring the transmitted wavefront error of the silicon entrance windows of the wavefront sensor cryostat. The technique can be readily applied to quantitative phase measurements in the near-infrared regime. Moreover, by employing a slightly off-axis optical setup, the proposed method can optimize the required spatial resolution and enable real time measurement capabilities. The feasibility of the proposed setup is demonstrated, followed by theoretical analysis and experimental results. Our experimental results show that the phase error repeatability in the nanometer regime can be achieved.
