摘要： Optical coherence tomography (OCT) is a well-established method to retrieve three-dimensional, cross-sectional images of biological samples in a non-invasive way using near-infrared radiation. The axial resolution of OCT is on the order of the coherence length lc ∝ λ 2 /Δλ which depends on the central wavelength λ0 and the spectral width Δλ of the light source. As a consequence, the axial resolution only depends on the spectrum rather than the geometrical properties of the radiation. OCT with broadband visible and near-infrared sources typically reaches axial (depth) resolutions on the order of a few micrometers [1]. Here we present extreme ultra violet (XUV) coherence tomography (XCT) [2], which takes advantage of the fact that the coherence length can be signi?cantly reduced if broadband XUV and soft X-ray (SXR) radiation is used. XCT can display its full capabilities when used in the spectral transmission windows of the sample materials. For instance, the silicon transmission window (30-99 eV) corresponds to a coherence length of about 12 nm, thus suggesting applications for semiconductor inspection. In the water window at 280-530 eV, a coherence length as short as 3 nm can be achieved and highlights possible applications of XCT for life sciences. XCT utilizes a variant of the Fourier-domain OCT scheme that completely avoids a beam splitter. In the experiment, broadband XUV from a lab-based high-harmonic generation light source [3] is focused onto the surface of the sample. The re?ected spectrum is measured with a grating spectrometer (see Fig. 1 left side). The top layer re?ection assumes the role of a reference beam. Previously, this simpli?cation led to artifacts [2]. Here we show a novel one-dimensional phase retrieval algorithm (PR) to mitigate such disadvantages and enable artifact-free so-called PR-XCT [4]. The right side of Fig. 1 shows a 3D-tomogram of a nondestructive XCT scan of two nanometer thin laterally structured gold layers embedded in silicon. An axial resolution of 24 nm could be reached in the silicon transmission window with the table-top system. Another remarkable result is the high material sensitivity of XCT. At a depth of about 160 nm, a Silicon dioxide layer (blue) was detected which developed during the production process of the sample and has a thickness of a few nanometers only. This layer could not be detected with a SEM in a thin slice cut out of the sample, and even in a TEM image it is only barely visible. Furthermore, the PR-XCT algorithm is capable of extracting material information about the materials inside of the sample. We will present ?rst results on material-resolved XCT.