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This contribution presents the design and implementation of a compact and robust Echelle-inspired cross-grating spectrometer which is arranged as a double pass setup. This allows use of the employed refractive elements for collimation of the incoming light and, after diffraction at the reflective crossed diffraction grating, for imaging the diffracted light onto the detector. The crossed diffraction grating combines the two dispersive functionalities of a classical Echelle spectrometer in a single element and is therefore formed by a superposition of two blazed linear gratings which are oriented perpendicularly. The refractive elements and the plane grating are arranged in a rigid objective group which is beneficial in terms of stability and robustness. The experimental tests prove that the designed resolving power of more than 300 is achieved for the addressed spectrum ranging from 400 nm to 1100 nm by using an entrance pinhole diameter of 105 µm. The utilization of a single mode fiber increases the resolving power to more than 1000, but leads to longer acquisition times.

The concept and the implementation of a compact and simplified echelle spectrometer are presented, and the working principle is demonstrated by first experimental measurements. The crucial element of the setup is a cross-grating, combining an echelle grating utilizing several higher diffraction orders (5th up to 11th) and a superposed perpendicular-oriented cross-dispersing grating. Two alternative manufacturing approaches for the cross-grating are presented and discussed. The first approach combines Talbot lithography for the deep echelle grating and interference lithography for the cross-dispersing structure. As a second approach, direct laser-beam writing was applied. The compact echelle spectrometer covers a spectral range from 380 to 700 nm and offers a spectral resolution of ∼2 .

Echelle inspired cross-grating spectrometers offer the potential to bridge the gap between classical high-end echelle spectrometers and curved-grating single-element instruments. In particular, the cross-grating approach offers the possibility to simultaneously achieve a high spectral resolution and a wide accessible spectral range in compact dimensions and without moving parts. We report on the complete realization and implementation details of an all-reflective cross-grating spectrometer based on a modified Czerny–Turner configuration including a folded beam path and a toric-convex mirror for aberration compensation. The applicability of the cross-grating spectrometer is demonstrated by test measurements including the recording of the spectra of different plant leaves. For the cross-grating spectrometer, with an accessible wavelength range between 330 and 1100 nm, a spectral resolution of 0.6 nm at 589 nm was achieved.

Echelle-inspired cross-grating spectrometers try to combine the high performance of classical Echelle spectrometers and the small footprint of compact line-grating spectrometers. Therefore, a cross-grating is used which is a superposition of two perpendicularly oriented line gratings in a single element. Highly resolved, but overlapping, diffractions orders are created by the main grating, which are separated by the cross-disperser. This powerful approach is connected to different challenges concerning the optical design, the fabrication of the cross-grating and implementation of the device. These challenges are addressed by a compact and rigid double-pass design, which utilizes the same refractive elements for collimation of the incoming beam and focusing of the diffracted light on the detector. This contribution gives an overview on the design and focusses on the implementation of the spectrometer. This includes on one hand the mounting of the cross-grating and the refractive elements in a rigid objective group and, on the other hand, the adjustment of the objective to the entrance fiber and the 2D detector. Furthermore, the implemented and calibrated instrument allows to conduct several validating experimental tests in order to proof the working principle. The spectrometer addresses a spectral range from 400 nm to 1100 nm and reaches a resolving power of 300 with an entrance pinhole diameter of 105 μm. An even higher resolving power of more than 1000 is reached with a reduced pinhole diameter of approximately 5 μm.