Suppression of Secondary Diffraction Maxima via Binarized Cosine Window Transmission Gratings

Transmission gratings are widely used in soft X-ray spectroscopy for laser-plasma diagnostics due to their structural simplicity, moderate spectral resolution, and broad bandwidth. However, secondary diffraction maxima located between the principal orders introduce spectral contamination and degrade measurement accuracy. In this work, we propose a binarized cosine window to replace conventional rectangular slit apertures in transmission gratings. Through theoretical analysis, numerical simulations, and visible-light experiments, we demonstrate that the proposed design effectively redistributes diffracted energy from secondary maxima into the principal maxima. Experimental results show a reduction of 93.12% in secondary peak intensity and an improvement of approximately 27.36 dB in signal-to-noise ratio. This suppression mechanism enhances both spectral resolution and measurement reliability, providing a practical approach for improving soft X-ray spectroscopic diagnostics. The proposed method offers a promising pathway for high-precision spectral analysis in applications such as high energy density physics and advanced materials research.