Calibrating photometric redshift measurements with the Multi-channel Imager (MCI) of the China Space Station Telescope (CSST)

The China Space Station Telescope (CSST) photometric survey aims to perform a high spatial resolution (~0.15'') photometric imaging for the targets that cover a large sky area (~17,500 deg^2) and wide wavelength range (from NUV to NIR). It expects to explore the properties of dark matter, dark energy, and other important cosmological and astronomical areas. In this work, we evaluate whether the filter design of the Multi-channel Imager (MCI), one of the five instruments of the CSST, can provide accurate photometric redshift (photo-$z$) measurements with its nine medium-band filters to meet the relevant scientific objectives. We generate the mock data based on the COSMOS photometric redshift catalog with astrophysical and instrumental effects. The application of upper limit information of low signal-to-noise ratio (SNR) data is adopted in the estimation of photo-z. We investigate the dependency of photo-z accuracy on the filter parameters, such as band position and width. We find that the current MCI filter design can achieve good photo-z measurements with accuracy sigma_z~0.017 and outlier fraction f_c~2.2%. It can effectively improve the photo-z measurements of the main CSST survey using the Survey Camera (SC) to an accuracy sigma_z~0.015 and outlier fraction f_c~1.5%. It indicates that the original MCI filters are proper for the photo-z calibration.

Optical, Thermal, and Mechanical Properties of (Y1-xScx)2O3 Transparent Ceramics

Sesquioxides such as Y2O3 and Sc2O3 are important optical materials, but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400 oC. In this work, a series of (Y1-xScx)2O3 transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives, and the effect of Scandium (Sc) content on the crystal structure and optical/thermal/mechanical properties were evaluated. Y2O3 and Sc2O3 form a complete solid solution with a cubic bixbyite structure. The formation of (Y1-xScx)2O3 solid solution promotes the densification of ceramics, leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35-8 mm. In particular, the in-line transmittance in the range of 0.6-6 mm remains above 80% for (Y1-xScx)2O3 with x = 0.23-0.31, while the pristine Y2O3 and Sc2O3 are opaque. Moreover, the mechanical properties including Vickers hardness (Hv), fracture toughness (KIC), and biaxial strength (δb) are evidently enhanced due to the solid solution strengthening, while the thermal conductivity is reduced due to the reduction of photon free path. This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxides transparent ceramics with high optical and mechanical quality.

Research on Next Generation Fiber Optical Amplifiers and Their Evaluation in Dense Communication Systems

In recent years, the information technology sector has developed rapidly and there has been a rapid increase in the amount of information transmitted. The demand for larger telecommunication network capacities is growing, therefore it is necessary to increase the number of channels and transmission speed in wavelength division multiplexed transmission systems. Various optical amplifiers can be used to compensate for the attenuation of the accumulated signal (over a wide wavelength range). The Doctoral Thesis did research on the use of EDFA, Raman, FOPA and combined optical amplifiers in wavelength division multiplexing systems. In the work, special emphasis is placed on erbium and ytterbium alloy fibers with the study of computer modeling of optical amplifiers in cladding pumping technology.

A full decade (2009-2019) of continuous nightglow observations from the NUV to the NIR

<p>The airglow emission of the mesopause region comprises molecular bands and atomic lines in the near-ultraviolet to the near-infrared wavelength range, e.g. the prominent roto-vibrational OH bands, a weak FeO/NiO continuum, the green OI line, the NaD doublet and some others. Since ground-based astronomical facilites observe through the Earth's atmosphere, the fingerprint of these emissions is visible in astronomical spectra taken with a telescope.<br>We have assembled a comprehensive data set of about 100,000 spectra in total taken between 1st of October 2009 and 30th of September 2019 with the X-shooter spectrograph, which is mounted at the Very Large Telescope in the Chilean Atacama desert (24.6°S, 70.4°W). This instrument provides medium-resolution spectra covering the entire wavelength range from 0.3 to 2.5μm simultaneously by incorporating three spectral subranges (UVB: 0.3-0.56μm; VIS: 0.56-1.02μm; NIR: 1.02-2.5μm).</p><p>The X-shooter instrument was continuously in operation during the covered period and frequently used by astronomers. Thus, the temporal coverage of the available observations is very dense for astronomical data allowing various airglow studies on time scales from minutes to a full decade. Due to the simultaneously observed wide wavelength range, individual airglow emitters as well as correlations between them can be investigated in detail (cf. Noll et al. 2021, this session, for more information).</p><p>In this presentation we describe the properties and the calibration of this unique data set.</p>