The Application of High-Order Harmonics to Extreme Ultraviolet Polarimetry

1. The Application of High-Order Harmonics to Extreme Ultraviolet Polarimetry N. Brimhall, J. C. Painter, M. Turner, R. S. Turley, M. Ware, J. Peatross Brigham Young University, Provo, UT 84602.

2. Overview Development of an instrument that utilizes laser generated high order harmonics as a source of extreme ultraviolet light for polarimetry. • Motivation/Applications • High Harmonics as an EUV source • Prototype Experiment • Full-scale instrument in progress

3. Motivation/Applications Astronomy, Lithography, Microscopy, Plasma Diagnostics IMAGE satellite Venus Express Mars Express http://euv.lpl.arizona.edu/euv/ http://www.esa.int/esaCP/index.html

4. A Problem is Discovered • The complex index of refraction (N = 1-δ+iβ) for one or more materials differed significantly from published values. • These values had to be re-measured to achieve the desired specifications. http://euv.lpl.arizona.edu/euv/

5. Inaccuracies in published optical constants Edges in published constants are different by as much as 3 eV from measured values. Graph of published optical constants of ThO2 versus measured values.

6. An EUV Polarimeter Based on High-Order Harmonics 800 nm, 35 fs, 10 mJ Ti:sapphire laser focused in He, Ne, Ar, or Xe gas produces EUV light Used in a polarimeter, this source is • Cheap • Tabletop • Local J. R. Sutherland et al, Optics Express 12, 4430-4436 (2004).

7. Specifications • hello

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12. Prototype Experiment • Demonstrated feasibility • Show that the source will have sufficient brightness to measure reflectances as low as 0.5%.

13. Full-scale instrument • Rotatable linear polarization • Increased scanning ability • Ability to measure reflectance of multiple wavelengths simultaneously

14. Scanning ability • hello

15. Questions we are addressing • Normalization of reflectances with a highly variable source. • Sample alignment • Determination of sample and detector angles and detected wavelengths • LabView programming for automated positioning • Comparison with other EUV reflectometers and polarimeters (plasma sources, synchrotron sources)

16. Conclusions/Summary • This project promises a useful research tool to the EUV thin-film researchers at BYU . • High harmonics as a source of EUV light constitute a broad range of wavelengths from 8 nm to 62 nm with a flux a factor of 200 times below that available at Beamline 6.3.2 at the Advanced Light Source, but a factor of 30,000 times brighter than a plasma source currently used at BYU. • The well-controlled polarization and the ability to measure reflectances simultaneously over a wide comb of wavelengths are clear advantages. • Our prototype instrument demonstrated the feasibility of this instrument and showed that we can measure reflectances as low as 0.5%.

17. Acknowledgements • Thanks to the high harmonics research group at Brigham Young University… • …including Sergei Voronov and Greg Harris for their work on the prototype instrument. • This project was supported by the National Science Foundation Grant #PHY-0457316 and by Brigham Young University.