  Spectral measurements play a vital role in understanding laser-plasma
interactions. The ability to accurately measure the spectrum of radiation
sources is crucial for unraveling the underlying physics. In this article, we
introduce a novel approach that significantly enhances the efficiency of binary
Sinusoidal Transmission Grating Spectrometers (STGS). The grating was tailored
especially for Extreme Ultraviolet (EUV) measurements. The new design, High
Contrast Sinusoidal Transmission Grating (HCSTG), not only suppresses high
diffraction orders and retains the advantageous properties of previous designs
but also exhibits a fourfold improvement in first-order efficiency. In
addition, the HCSTG offers exceptional purity in the first order due to
effectively eliminating half-order contributions from the diffraction pattern.
The HCSTG spectrometer was employed to measure the emission of laser-produced
Sn plasma in the 1-50 nm spectral range, achieving spectral resolution of
$\lambda/\Delta\lambda=60$. We provide a comprehensive analysis comparing the
diffraction patterns of different STGs, highlighting the advantages offered by
the HCSTG design. This novel, enhanced efficiency HCSTG spectrometer, opens new
possibilities for accurate and sensitive EUV spectral measurements.
