Work

Single-exposure geometry-constrained volumetric reconstruction of NA = 0.19 EUV focal fields

Year: 2026

Type: article

Abstract: The trend toward increasing numerical aperture (NA) in extreme ultraviolet (EUV) focusing necessitates precise, single-exposure characterization of the three-dimensional focal field. However, conventional Hartmann wavefront sensing is fundamentally challenged in the high-NA regime, where minor calibration errors couple into steep reference wavefronts, generating substantial fictitious phase artifacts. Here, we present a geometry-constrained reconstruction framework that robustly synthesizes the complete 3D focal volume of an NA = 0.19 Schwarzschild objective. Rather than relying on calibration-error-sensitive phase integration, we exploit the geometric signatures of the primary two-bounce beam and a parasitic four-bounce ghost beam specific to Schwarzschild-type concentric cavities. Resolving these geometrically defined constraints within an exact 3D non-linear ray-tracing framework allows for the deterministic extraction of the macroscopic optical alignment state, establishing a pathway for online objective adjustment. Coupling this resolved geometry with the measured intensity distribution accurately maps the principal fluence envelope. Propagating this stabilized field via a vectorial Debye integration generates a precise volumetric dose mapping. Sub-micron spatial registration of this reconstructed dose map with experimental ablation imprints robustly validates the model’s physical fidelity in predicting morphological damage thresholds. This approach broadens the usable scene for the Hartmann wavefront sensor into calibration-hostile, NA = 0.19 Schwarzschild objective systems, enabling single-exposure access to fluence-dependent damage evolution.

Source: Optics Express

DOI: 10.1364/oe.609617