Fig. 2: Measurements of the XPDC cone.
From: X-ray parametric down-conversion reveals EUV-polariton
a–c Circular scattering patterns recorded for phase-matching at ∆Ωa = 0.47°, ∆Ωb = 1.07° and ∆Ωc = 1.87° above the elastic (111)-reflection in diamond, respectively. All data is background subtracted and plotted on a common color scale. Cone openings amount to 0.97°, 1.20° and 0.62° in diameter, respectively. d Enhanced contrast (divergent color scale) visualizes the excellent agreement of measured XPDC with its theoretically predicted signature (green, ellipsoidal wire-frame) across the complete phase-matching region (∆Ω = [0.27, … 1.87°]). Projections of the ellipsoid are shown in gray. The striking two-fold modulation of the scattering pattern can be related to different polaritonic contributions to XPDC (red/blue: predominantly upper branch/lower branch).
