The reformatting advantage: photonics vs conventional optics!

Abstract

In recent decades, spectroscopic capabilities have been significantly enhanced by new technological developments, in particular spatial reformatting. Spatial reformatting allows multiple functionalities: the observation of a larger area of sky, obtaining the spectra of all spatial elements under the same atmospheric conditions; modification of the shape and size of the field of view; focal-ratio conversion for the optimized coupling between the telescope and the spectrograph; increase in the spatial and spectral resolving power; the observation of multiple objects; homogeneity in the illumination; scrambling of spatial and/or phase induced structure with the instrument, thus improving the system stability; relocation of the exit pupil, especially important for telecentric systems. The impact of reformatting and the breadth of science cases is so great that many alternative methods and technologies have been proposed: image slicers using refractive or reflective solutions; optical fibers with different core sizes and geometries; microlenses used in isolation or combined with fibers and more recently, photonic devices such as Photonic lanterns to produce modal decomposition. In this paper, a comparison between all currently available options is presented, with a detailed analysis of their advantages and limitations and a proposal for a new reformatter combining slicers and photonic devices. This proposal presents the advantages of the other alternatives and additionally offers: minimization of focal-ratio degradation; produces image and modal decomposition; improves the throughput along the spectral range, increases the spectral resolving power and adds the functionality of scrambling. All of these advantages are combined in a system where photonic and astronomical instrumentation capabilities are joined in an innovative solution with many applications, like for example, the Extremely Large Telescope.

High-speed optical imaging with sCMOS pixel reassignment

“…In this study, we utilized image reformatting with flexible fiber optic pixel reassignment to take advantage of the rapid line readout capability inherent in sCMOS sensors. Despite their wide-ranging applications in imaging and sensing, such as endoscopy and spectroscopy, among others [87][88][89][90][91][92][93][94][95][96][97][98][99][100] , fiber optic relays have not previously been harnessed to exploit this feature. Thus, sHAPR presents users with the opportunity to enhance imaging speed while having the flexibility to rearrange pixels to achieve the most suitable FOV for their application.…”

Multi-core fibre-fed integral field spectrograph (MCIFU) IV: the fiber link

“…This is leading to proposals for alternative instruments, using different methods, which interestingly is in line with the older development of conventional IFUs. 4 Recently, several single-mode (SM) fiber-fed instruments have been proposed. [5][6][7][8] These take advantage of the spatial filtering properties of SM fibers, increasing the contrast between the star and planet.…”