Slicer Integral Field Unit Research Articles

Development of micro-mirror slicer integral field unit for space-borne solar spectrographs

We present an innovative optical design for image slicer integral field unit (IFU) and a manufacturing method that overcomes optical limitations of metallic mirrors. Our IFU consists of a micro-mirror slicer of 45 arrayed, highly narrow, flat metallic mirrors and a pseudo-pupil-mirror array of off-axis conic aspheres forming three pseudo slits of re-arranged slicer images. A prototype IFU demonstrates that the final optical quality is sufficiently high for a visible light spectrograph. Each slicer micro-mirror is 1.58 mm long and 30 $$\upmu$$ m wide with surface roughness $$\le$$ 1 nm rms, and edge sharpness $$\le$$ 0.1 $$\upmu$$ m, etc. This IFU is small size and can be implemented in a multi-slit spectrograph without any moving mechanism and fore optics, in which one slit is real and the others are pseudo slits from the IFU. The IFU mirrors were deposited by a space-qualified, protected silver coating for high reflectivity in visible and near IR wavelength regions. These properties are well suitable for space-borne spectrograph such as the future Japanese solar space mission SOLAR-C. We present the optical design, performance of prototype IFU, and space qualification tests of the silver coating.

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.