skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Shack-Hartmann wavefront sensor measurement for dynamic temperature profiles in heat-capacity laser rods

Abstract

A Shack-Hartmann sensor nonintrusive measurement for the temperature profile in a heat-capacity neodymium-doped glass rod is proposed. This technique is possible because the optical path length of the rod changes with temperature linearly over a wide range. The temperature change of the solid-state laser rod is often recorded by using a thermocouple, thermal camera, or phase-shifting interferometer. Based on an analysis of temperature-induced changes in length and index of refraction, we can get the temperature profiles from the wavefront reconstructions in real time. The results suggest the Shack-Hartmann sensors could replace microbolometer-based thermal cameras and phase-shifting interferometers for dynamic temperature profiles in heat-capacity laser rods with particular advantages. A strange temperature chaos of the Nd:glass rod just after the pump cycle is discovered.

Authors:
; ; ;
Publication Date:
OSTI Identifier:
20929735
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Optics; Journal Volume: 46; Journal Issue: 15; Other Information: DOI: 10.1364/AO.46.002963; (c) 2007 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOLOMETERS; CAMERAS; DOPED MATERIALS; GLASS; INTERFEROMETERS; MEASURING METHODS; NEODYMIUM; REFRACTIVE INDEX; RODS; SOLID STATE LASERS; SPECIFIC HEAT; TEMPERATURE MEASUREMENT; THERMOCOUPLES

Citation Formats

Wang Xiaobo, Xu Xiaojun, Lu Qisheng, and Xi Fengjie. Shack-Hartmann wavefront sensor measurement for dynamic temperature profiles in heat-capacity laser rods. United States: N. p., 2007. Web. doi:10.1364/AO.46.002963.
Wang Xiaobo, Xu Xiaojun, Lu Qisheng, & Xi Fengjie. Shack-Hartmann wavefront sensor measurement for dynamic temperature profiles in heat-capacity laser rods. United States. doi:10.1364/AO.46.002963.
Wang Xiaobo, Xu Xiaojun, Lu Qisheng, and Xi Fengjie. Sun . "Shack-Hartmann wavefront sensor measurement for dynamic temperature profiles in heat-capacity laser rods". United States. doi:10.1364/AO.46.002963.
@article{osti_20929735,
title = {Shack-Hartmann wavefront sensor measurement for dynamic temperature profiles in heat-capacity laser rods},
author = {Wang Xiaobo and Xu Xiaojun and Lu Qisheng and Xi Fengjie},
abstractNote = {A Shack-Hartmann sensor nonintrusive measurement for the temperature profile in a heat-capacity neodymium-doped glass rod is proposed. This technique is possible because the optical path length of the rod changes with temperature linearly over a wide range. The temperature change of the solid-state laser rod is often recorded by using a thermocouple, thermal camera, or phase-shifting interferometer. Based on an analysis of temperature-induced changes in length and index of refraction, we can get the temperature profiles from the wavefront reconstructions in real time. The results suggest the Shack-Hartmann sensors could replace microbolometer-based thermal cameras and phase-shifting interferometers for dynamic temperature profiles in heat-capacity laser rods with particular advantages. A strange temperature chaos of the Nd:glass rod just after the pump cycle is discovered.},
doi = {10.1364/AO.46.002963},
journal = {Applied Optics},
number = 15,
volume = 46,
place = {United States},
year = {Sun May 20 00:00:00 EDT 2007},
month = {Sun May 20 00:00:00 EDT 2007}
}
  • A Shack-Hartmann wavefront sensor (SWHS) splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. The accuracy of the centroid measurement determines the accuracy of the SWHS. Many methods have been presented to improve the accuracy of the wavefront centroid measurement. However, most of these methods are discussed from the point of view of optics, based on the assumption that the spot intensity of the SHWS has a Gaussian distribution, which is not applicable to the digital SHWS. In this paper, we present a centroid measurement algorithm based on the adaptive thresholding andmore » dynamic windowing method by utilizing image processing techniques for practical application of the digital SHWS in surface profile measurement. The method can detect the centroid of each focal spot precisely and robustly by eliminating the influence of various noises, such as diffraction of the digital SHWS, unevenness and instability of the light source, as well as deviation between the centroid of the focal spot and the center of the detection area. The experimental results demonstrate that the algorithm has better precision, repeatability, and stability compared with other commonly used centroid methods, such as the statistical averaging, thresholding, and windowing algorithms.« less
  • We developed a new, to the best of our knowledge, test method to measure the wavefront error of the high-NA optics that is used to read the information on the high-capacity optical data storage devices. The main components are a pinhole point source and a Shack-Hartmann sensor. A pinhole generates the high-NA reference spherical wave, and a Shack-Hartmann sensor constructs the wavefront error of the target optics. Due to simplicity of the setup, it is easy to use several different wavelengths without significant changes of the optical elements in the test setup. To reduce the systematic errors in the system,more » a simple calibration method was developed. In this manner, we could measure the wavefront error of the NA 0.9 objective with the repeatability of 0.003{lambda} rms ({lambda}=632.8 nm) and the accuracy of 0.01{lambda} rms.« less
  • The wavefront of the radiation of two types from high-power solid-state (Ti:sapphire and Nd:glass) lasers is experimentally studied. The measurements are performed using a Shack - Hartmann wavefront sensor. The technical and functional potential of this sensor in measuring laser-based schemes is demonstrated. The results of measuring both static and dynamic wavefront aberrations are discussed. The estimated dynamics of defocus aberration is in agreement with the experimental data. (measurement of laser radiation parameters)
  • We propose a simple and powerful algorithm to extend the dynamic range of a Shack-Hartmann wave-front sensor. In a conventional Shack-Hartmann wave-front sensor the dynamic range is limited by the f-number of a lenslet, because the focal spot is required to remain in the area confined by the single lenslet. The sorting method proposed here eliminates such a limitation and extends the dynamic range by tagging each spot in a special sequence. Since the sorting method is a simple algorithm that does not change the measurement configuration, there is no requirement for extra hardware, multiple measurements, or complicated algorithms. Wemore » not only present the theory and a calculation example of the sorting method but also actually implement measurement of a highly aberrated wave front from nonrotational symmetric optics.« less
  • A table top extreme ultraviolet (EUV)-source was developed at Laser-Laboratorium Goettingen for the characterization of optical components and sensoric devices in the wavelength region from 11 to 13 nm. EUV radiation is generated by focusing the beam of a Q-switched Nd:YAG laser into a pulsed xenon gas jet. Since a directed gas jet with a high number density is needed for an optimal performance of the source, conical nozzles with different cone angles were drilled with an excimer laser to produce a supersonic gas jet. The influence of the nozzle geometry on the gas jet was characterized with a Hartmann-Shackmore » wave front sensor. The deformation of a planar wave front after passing the gas jet was analyzed with this sensor, allowing a reconstruction of the gas density distribution. Thus, the gas jet was optimized resulting in an increase of EUV emission by a factor of two and a decrease of the plasma size at the same time.« less