Slicer Mirror Research Articles

Design of the VLT-CUBES image slicers:

CUBES is a high efficiency spectrograph designed for a Cassegrain focus of the Very Large Telescope and is expected to be in operation in 2028. It is designed to observe point or compact sources in a spectral range from 300 to 405nm. CUBES will provide two spectral resolving powers: Rge20,000 for high resolution (HR) and Rge5,000 for low resolution (LR). This is achieved by using an image slicer for each resolution mode. The image slicers re-format a rectangular on-sky field of view of either 1.5arcsec by 10arcsec (HR) or 6arcsec by 10arcsec (LR) into six side-by-side slitlets which form the spectrograph slit. The slit dimensions are 0.19mm times 88mm for HR and 0.77mm times 88mm for LR. The on-sky and physical widths of the slicer mirrors are 0.25arcsec/0.5mm (HR) and 1arcsec/2mm (LR). The image slicers reduce the spectrograph entrance slit etendue and hence the size of the spectrograph optics without associated slit losses. Each of the proposed image slicers consists of two arrays of six spherical mirrors (slicer mirror and camera mirror arrays) which provide a straight entrance slit to the spectrograph with almost diffraction-limited optical quality. This paper presents the description of the image slicers at the end of the Phase A conceptual design, including their optical design and expected performance.

Broadband aberration-corrected snapshot spectrometer with a toroidal slicer mirror.

We demonstrate a broadband aberration-corrected snapshot spectrometer by developing a toroidal slicer mirror as the focusing mirror. A collimating slicer mirror and an integrated grating divide the entire wavelength range into several windows. The toroidal sub-mirrors of the focusing mirror compensate for the coma and correct the astigmatism at different windows to compress the spectral spots over the waveband. From 200 to 1000nm, the RMS spot radii are less than 30μm and the spectral resolution at 600nm is 151.8pm. The optics have a small volume of 11 cm×11 cm×1.5 cm by employing a folded structure.

Broadband snapshot spectrometer based on spliced spectra

Wavelength scanning in broadband spectrometers has limitations on transient imaging and instrument size. We demonstrate a broadband snapshot spectrometer scheme by developing an integrated grating with n different blaze angles on one substrate and a slicer mirror to provide high diffraction intensities in a wide wavelength range. A slicer mirror divides the entire spectrum into n windows, with each window containing a blazed wavelength. The spectra can be spliced and detected by an area-array detector at one exposure. Using this method, we designed and optimized a snapshot spliced-spectrum spectrometer that numerically covers 200–1000 nm wavelength range with a spectral resolution of 0.27 nm.

Compact optical multipass matrix system design based on slicer mirrors.

High path-to-volume ratio (PVR) and low-aberration-output beams are the two main criteria to assess the performance of multipass absorption cells. However, no substantial progress has been reported for large-numerical-aperture-coupled multipass cells, which is due to the accumulated aberrations caused by a large number of off-axis reflections. Based on Chernin's design, in this study, we modified Chernin's four-objective multipass matrix cell by using slicer mirrors to eliminate alignment difficulty and decrease the system volume. A generalized design routine based on user requirements is also proposed. Based on the automatic modeling tool package (Pyzdde) connected with Zemax and boundary conditions of the parameters selection proposed, a low-aberration-output beam and a high PVR are easily obtained compared with other multipass cells schemes. In one demo design, 108 passes (5×7 matrix spots) in a base length of 300mm are presented. The PVR and peak-to-valley value wavefront errors are 67.5m/L and 0.92μm, respectively. Finally, a tolerance analysis of this optical multipass system is also presented. This work may provide better broadband optical absorption cells in terms of response time and a better detection sensitivity in versatile applications.

An Image Slicer Integral Field Unit with Diffraction‐limited Performance for Three‐Dimensional Imaging Spectroscopy

ABSTRACTWe have designed and constructed an advanced image slicer (AIS) integral field unit (IFU). The IFU employs an all‐mirror design and will be installed in the Penn State near‐IR Imager and Spectrograph (PIRIS) for three‐dimensional integral field spectroscopy at various astronomical telescopes. Using the AIS technique, the slicer IFU can preserve the telescope’s focal ratio and pupil (both position and size) while maximizing the packing efficiency for three‐dimensional data on the detector. Compared to other existing AIS IFU designs, our design, which uses monolithic optical components for both pupil and field mirror arrays, provides a convenient engineering solution for manufacturing, using the state‐of‐the‐art diamond‐turning machines and alignment of the IFU optics. Our slicer mirror array was also manufactured by diamond turning, with all the mirrors simultaneously machined, which also simplifies the procedure for the manufacture and the assembly of the mirrors. We present the IFU optical description, component test results, and overall IFU system performance. We also discuss possible science applications using the IFU.