Overview of High-Efficiency Transmission Gratings for Molecular Spectroscopy

Most diode array–based diffractive spectrometers for the ultraviolet (UV), visible (vis), and near-infrared (NIR) spectral ranges use reflection-type diffraction gratings and are generally optimized for high resolution rather than high optical throughput. During the past 5–10 years, transmission-type gratings have been developed that provide near 100% efficiency for any polarization. These gratings have found widespread use for Raman spectroscopy and astronomy, where very little light is available, but elsewhere the awareness of the distinct benefits provided by transmission gratings seems quite limited. The purpose of this article is to provide a basic overview of the capabilities of transmission gratings optimized for molecular spectroscopy. Specifically, we will describe the two most commonly used types of gratings: the surface relief transmission grating (SRTG) and the volume phase hologram (VPH).