Echelle Grating Spectroscopic Technology for High-Resolution and Broadband Spectral Measurement

Abstract

Echelle grating provides high spectral resolving power and diffraction efficiency in a broadband wavelength range by the Littrow mode. The spectrometer with the cross-dispersed echelle scheme has seen remarkable growth in recent decades. Rather than the conventional approach with common blazed grating, the cross-dispersed echelle scheme achieves the two-dimensional spatial distribution of the spectrum by one exposure without scanning in the broadband spectral range. It is the fastest and most sensitive spectroscopic technology as of now, and it has been extensively applied in commercial and astronomical spectrometers. In this review, we first highlight the characteristics of the echelle and then present the optical layout, detection approach, and method of calibration. Finally, we discuss the state-of-the-art implementations and applications of commercial and astronomical instruments.

Improvements in VPHGs for astronomy based on photopolymers

“…Indeed, the maximum spectral range depends on the detector size once the dispersion is set and it cannot exceed λ -2λ if we want to avoid diffraction orders contamination. Usually these limits are overcome employing the echelle spectrograph, which exploits the high orders diffraction followed by a cross-dispersion of the orders to fill the detector 50 . We have proposed two configurations: i) a dual order VPHG to cover a very wide spectral range at low dispersion in a single exposure avoiding the order contamination; ii) a stacked VPHG to mimic an echellete grating.…”