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Extrinsic silicon and germanium detectors
Published in Antoni Rogalski, Infrared and Terahertz Detectors, 2019
The development and manufacture of extrinsic photodetectors are mainly concentrated in the United States. The programs on the use of off-atmospheric astronomy have spread especially intensively after the outstanding success of the Infrared Astronomical Satellite (IRAS) [6,7], which used 62 discrete photodetectors arranged in the focal plane. A number of National Aeronautics and Space Administration (NASA)- and National Science Foundation (NSF)-supported programs have been initiated by various research centers and universities. The array manufacturers have taken a strong interest and have done far more for astronomers than they might have anticipated [8,9]. They are Raytheon Vision Systems, DRS Technologies, and Teledyne Imaging Sensors [10,11]. A deep cooled space telescope located in vacuum can cover the entire IR range from 1 to 1,000 μm. Far-infrared astronomy provides key information about the formation and evolution of galaxies, stars, and planets. The low level of background irradiation makes it possible to improve the sensitivity of such systems by increasing the integration time (to hundreds of seconds).
Photon Detectors
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
The InSb photovoltaic detectors are widely used for ground- and space-based infrared astronomy. For applications in astrophysics, these devices are very often operated at 4–7 K with a resistive or capacitive transimpedance amplifier to achieve the lowest noise performance. At these low temperatures, the InSb photodiode resistance is so high that the detector Johnson noise is negligible, and the dominant noise sources are either the feedback resistance or input amplifier noise. Since the latter scales directly with the combined detector and input circuit capacitance, it becomes important to minimise them.
Parallel adaptive high-order CFD simulations characterising SOFIA cavity acoustics
Published in International Journal of Computational Fluid Dynamics, 2016
Michael F. Barad, Christoph Brehm, Cetin C. Kiris, Rupak Biswas
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne, 2.5-m infrared telescope mounted in a large open cavity in the aft fuselage of a Boeing 747SP, as shown in Figure 1(a). The aircraft typically flies high in the atmosphere, between 12 and 14 km (39,000 to 45,000 feet), reducing atmospheric distortion and enabling high quality images. SOFIA is a joint research program between NASA and the German Aerospace Center (DLR). In this work, we focus on (1) noise generation and flow physics in the open cavity where the telescope is mounted, and (2) assessment of solver parallel performance for up to 32 k cores for this multi-scale, demanding application with a complex geometry.
Cross-dispersed in-fibre spectrometer based on helix core bundle
Published in Journal of Modern Optics, 2019
Andreas Stoll, Ziyang Zhang, Kai Sun, Kalaga Madhav, Julia Fiebrandt, Martin M. Roth
In past years, much research effort has been dedicated to the development of compact spectrometers as (de)multiplexers for the wavelength division multiplexing (WDM) optical network but also as miniature wavelength interrogators in optical sensing applications. The most prominent devices are arrayed waveguide gratings (AWG) (1) and echelle-gratings based on planar lightwave circuits (PLCs) (2). In near-infrared astronomy, integrated photonic spectrographs adopting AWGs as key elements have been successfully demonstrated (3). While PLC-based spectrometers have been well-developed and prove to be very reliable, their functionality is limited in that the resolved wavelengths can only be mapped to a single image line due to the two-dimensional (2D) nature of the device. Multilayer photonic circuit designs can partially solve the problem by stacking several structures on one optical chip (4). However, the issue of planarity remains as the waveguides in each layer are still confined to their respective plane. Recent development in the field of ultrafast waveguide inscription technology (5–9) has opened up possibilities for the fabrication of truly three-dimensional (3D) photonic devices. Laser inscription of waveguides has been achieved in various materials, such as diamond and polymers (10, 11). In the field of astrophotonics, complex structures such as photonic lanterns and waveguide fan-outs have been experimentally demonstrated using direct laser inscription (12, 13). Further efforts have been made to realize integrated photonic systems all confined in optical fibres (14–16), thereby introducing the lab-in-fibre concept. An obvious advantage of such devices is the absence of fibre-chip interfaces, which can be problematic due to coupling losses, critical requirements for coupling techniques and instability of bonding material, especially considering operation at cryogenic temperatures.