XUV Coherence Tomography with Nanoscale Resolution · XUV Coherence Tomography with Nanoscale...
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XUV Coherence Tomography with Nanoscale Resolution S Fuchs 1 , J J Abel 1 , M Wuensche 1 , J Nathanael 1 , and G G Paulus 1,2 1 Helmholtz Institut Jena, Jena, Germany 2 Institute of Optics and Quantum Electronics, Friedrich-Schiller-Universität Jena, Jena, Germany Contact Email: [email protected] Figure 1: XUV coherence tomogram of a sample consist- ing of two structured gold layers buried in silicon at a depth of 230 and 330 nm. In addition, we detected an oxide layer at 170 nm that was inadvertently created dur- ing the production of the sample. Only the sensitivity of a transmission electron microscope (TEM) was sufficient to verify the XCT scan. For the TEM the sample had to destroyed The use of extreme ultraviolet (XUV) radia- tion for nano-scale imaging has distinctive advan- tages: it is label-free, affords high contrast, allows material identification and penetrates opaque mat- ter. Recent advances in the laser-based genera- tion of high-flux XUV radiation render this imag- ing modality accessible to a growing number of users. At the same time, unique properties such as ultrafast temporal resolution attract the interest of more and more scientists. On the other hand, there are challenges: Laser-based XUV radiation usually has broad spectra while XUV imaging reg- ularly calls for monochromatic radiation. In addi- tion, cross-sectional imaging is a challenge. Both challenges can be overcome by coher- ence tomography. In the visible spectral range, optical coherence tomography (OCT) has found widespread applications since its invention in 1990. For example, OCT is a standard diagnostic tech- nique at ophthalmologists’ offices to date. Being a variant of white-light interferometers, the reso- lution of OCT scales with the square of the wave- length and the inverse of the bandwidth. This sug- gests that XUV coherence tomography can achieve nanometer resolution. We report on the first demonstration of XUV coherence tomography (XCT) with a broadband high- harmonic source and show that XCT with nanometer depth resolution is indeed feasible. Moreover, XCT turns out to be highly sensitive and thus represents a very competitive non-invasive cross-sectional nano- scale imaging method that efficiently exploits broadband XUV radiation. A three-step phase retrieval algorithm allows using simple schemes while eliminating artifacts.
Transcript of XUV Coherence Tomography with Nanoscale Resolution · XUV Coherence Tomography with Nanoscale...
XUV Coherence Tomography with Nanoscale Resolution
S Fuchs1, J J Abel1, M Wuensche1, J Nathanael1, and G G Paulus1,2
1Helmholtz Institut Jena, Jena, Germany2Institute of Optics and Quantum Electronics, Friedrich-Schiller-Universität Jena, Jena, Germany
Contact Email: [email protected]
Figure 1: XUV coherence tomogram of a sample consist-ing of two structured gold layers buried in silicon at adepth of 230 and 330 nm. In addition, we detected anoxide layer at 170 nm that was inadvertently created dur-ing the production of the sample. Only the sensitivity ofa transmission electron microscope (TEM) was sufficientto verify the XCT scan. For the TEM the sample had todestroyed
The use of extreme ultraviolet (XUV) radia-tion for nano-scale imaging has distinctive advan-tages: it is label-free, affords high contrast, allowsmaterial identification and penetrates opaque mat-ter. Recent advances in the laser-based genera-tion of high-flux XUV radiation render this imag-ing modality accessible to a growing number ofusers. At the same time, unique properties suchas ultrafast temporal resolution attract the interestof more and more scientists. On the other hand,there are challenges: Laser-based XUV radiationusually has broad spectra while XUV imaging reg-ularly calls for monochromatic radiation. In addi-tion, cross-sectional imaging is a challenge.
Both challenges can be overcome by coher-ence tomography. In the visible spectral range,optical coherence tomography (OCT) has foundwidespread applications since its invention in 1990.For example, OCT is a standard diagnostic tech-nique at ophthalmologists’ offices to date. Beinga variant of white-light interferometers, the reso-lution of OCT scales with the square of the wave-length and the inverse of the bandwidth. This sug-gests that XUV coherence tomography can achievenanometer resolution.
We report on the first demonstration of XUV coherence tomography (XCT) with a broadband high-harmonic source and show that XCT with nanometer depth resolution is indeed feasible. Moreover, XCTturns out to be highly sensitive and thus represents a very competitive non-invasive cross-sectional nano-scale imaging method that efficiently exploits broadband XUV radiation. A three-step phase retrievalalgorithm allows using simple schemes while eliminating artifacts.
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