Multiple-Diffraction Subtractive Double Monochromator with High Resolution and Low Stray Light

Spectrometers play a crucial role in photonic applications, but their design involves trade-offs related to miniaturization, spectral fidelity, and their measurement dynamic range. We demonstrated a high-resolution, low-stray-light spectrometer with a compact size comprising two symmetric multiple-diffraction monochromators. We analyzed the spectral resolution and stray light and built a platform with two double-diffraction monochromators. Multiple diffractions on one grating increased the spectral resolution without volumetric expansion, and the subtractive double-monochromator configuration suppressed stray light effectively. The simulation and experimental results show that compared with single diffraction, repeated diffractions improved the resolution by 5–7 times. The spectral resolution of the home-built setup was 18.8 pm at 1480 nm. The subtractive double monochromator significantly weakened the stray light. The optical signal-to-noise ratio was increased from 34.76 dB for the single monochromator to 69.17 dB for the subtractive double monochromator. This spectrometer design is promising for broadband high-resolution spectral analyses.