Abstract
We present an overview of recent results on optical coherence tomography with the use of extreme ultraviolet and soft X-ray radiation (XCT). XCT is a cross-sectional imaging method that has emerged as a derivative of optical coherence tomography (OCT). In contrast to OCT, which typically uses near-infrared light, XCT utilizes broad bandwidth extreme ultraviolet (XUV) and soft X-ray (SXR) radiation (Fuchs et al in Sci Rep 6:20658, 2016). As in OCT, XCT’s axial resolution only scales with the coherence length of the light source. Thus, an axial resolution down to the nanometer range can be achieved. This is an improvement of up to three orders of magnitude in comparison to OCT. XCT measures the reflected spectrum in a common-path interferometric setup to retrieve the axial structure of nanometer-sized samples. The technique has been demonstrated with broad bandwidth XUV/SXR radiation from synchrotron facilities and recently with compact laboratory-based laser-driven sources. Axial resolutions down to 2.2 nm have been achieved experimentally. XCT has potential applications in three-dimensional imaging of silicon-based semiconductors, lithography masks, and layered structures like XUV mirrors and solar cells.
Highlights
Optical Coherence Tomography (OCT) is a well-established technique providing cross-sectional imaging of samples in a non-invasive and contact-free manner using infrared and visible light [1, 2]
When the sample is irradiated with broad bandwidth XUV coherence tomography (XCT) utilizes broad bandwidth extreme ultraviolet (XUV) radiation, the reflected spectrum exhibits well-defined modulation frequencies Δ depending on the depths of the layers
high-harmonic generation (HHG) source, (2) laser-plasma sources (LPS) source, (3) in nm; limited by width of the spectral filter, (4) Kaiser–Bessel window, (5) Gaussian window, (6) [27], (7) [41, 42], and (8) e.g., ΔE = 20 − 280 eV [36], ΔE = 250 − 3000 eV [43], 4 Discussion In Table 1, we summarize the most important features of different realizations of the coherence tomography experiments in the XUV/soft X-ray (SXR) regime
Summary
Optical Coherence Tomography (OCT) is a well-established technique providing cross-sectional imaging of samples in a non-invasive and contact-free manner using infrared and visible light [1, 2]. The lateral resolution is limited by the focus spot size provided by the conventional imaging, whereas the axial resolution is equivalent to the coherence length of the radiation source. In the near-infrared regime with a central wavelength of 0 = 1 m and a bandwidth of Δ = 400 nm , the axial resolution is limited to 1.1 m. This resolution is sufficient to investigate, for example, retinal structures, imaging of nanoscaled objects like semiconductor structures is out of reach.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
