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8: Layout of the imaging part of the system. BFP : Back Focal Plane, FFP : Front Focal Plane. In blue : ray tracing for the real image of the sample, in red : ray tracing for the imaging of the back focal plane of the objective
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With the constant decrease of the size of the transistors in microelectronics, the characterization tools have to be more and more accurate and have to provide higher and higher throughput. Semiconductor manufacturing being a layer-by-layer process, the fine positioning of the stack is crucial. The misalignment of the stack is called overlay and we...
Citations
... The vortices sketched in Fig. 1d are of charge + 1. Experimentally, this prediction implies a significant challenge: to precisely track the polarization response not just at a single wave- length, but across the entire leaky wave dispersion surface, that is, as a function of polar (θ) and azimuthal (ϕ) angle while matching, for each angular setting, the frequency to the leaky wave dispersion relation. Rather than using a traditional ellipsometry technique we use a polarimetric k-space imaging scheme [16][17][18][19][20] , as shown in Fig. 1e. This offers the crucial advantage of measuring all angles of incidence that fit the numerical aperture (NA) of a microscope objective in parallel on a charge-coupled device, without needing any scanned rotation stage. ...
... To observe this vortex, we measure the full polarization state for each wavelength λ and each wavevector k x and k y . This would be extremely tedious with a traditional ellip- someter that scans angle by angle, but is straightforward with our k-space imaging technique by using a linear polarizer and a QWP introduced into the detection arm as a Stokes polarimeter 17,20 . We summarize the polarization ellipse of reflected light by the orienta- tion α of its major axis relative to the x axis and the ellipticity angle χ (for definitions see Fig. 2a). ...
Optical bound states in the continuum (BICs) are states supported by a photonic structure that are compatible with free-space radiation, yet become perfectly bound for one specific in-plane momentum and wavelength1,2. Recently, it was predicted that light radiated by such modes around the BIC momentum–frequency condition should display a vortex in its far-field polarization profile, making the BIC topologically protected³. Here, we study a one-dimensional grating supporting a transverse magnetic mode with a BIC near 700 nm wavelength, verifying the existence of the BIC using reflection measurements, which show a vanishing reflection feature. Using k-space polarimetry, we measure the full polarization state of reflection around the BIC, highlighting the presence of a topological vortex. We use an electromagnetic dipole model to explain the observed BIC through destructive interference between two radiation channels, characteristic of a Friedrich–Wintgen-type BIC⁴. Our findings shed light on the origin of BICs and verify their topological nature.
