Abstract

Precision spectroscopy in the mid-infrared (MIR) region is of great importance for many applications including breath diagnosis and astronomical spectroscopy as various molecular vibrational modes exist in this region. A mid-infrared comb combined with a broadband comb-resolved spectrometer can be a promising method to do this since target gas contains multiple molecular species in most applications. A two-dimensional array detector and highly dispersive diffraction optics such as a virtually-imaged phased array (VIPA) achieved such a spectrometer[1]. Although VIPAs are a powerful tool to fulfill both high resolution and broad bandwidth, the diffraction efficiency cannot be very high in principle. On the other hand, echelle gratings can realize relatively high diffraction efficiency, but the use for broadband comb-resolved spectroscopy has been limited because of their diffraction order of a few hundred[2]. In this study, we constructed a high-throughput spectrometer for a 1-GHz comb by developing an extremely-high-order germanium immersion echelle grating (EGIG).

© 2017 IEEE