The fiber-fed High Resolution Spectrograph of the Chinese Xinglong 2.16-m Telescope is the main instrument for high precision spectral detection in China. In order to improve the observation performance, a wavelength calibrator based on Fabry-P´erot etalon (FPE) is developed. Here, we report on the design, transmission charac-teristics and vacuum-thermostatic performance of the system. To meet the requirements of the calibration, the calibrator is custom-designed with the FPE gap of 5 mm, fineness value of 40, and illuminating fiber of 100 μm in diameter, which could generate calibration lines with 30 GHz in lines space and covering 500 – 700 nm.
"A joint project has been proposed by the Chinese and Spanish astronomy communities, to develop a high-resolution, ultra- stable spectrograph for the Gran Telescopio Canarias (GTC) at La Palma. Being expected to conduct precise radial velocity (PRV) measurement with extreme precision of up to 10 cm s−1, the instrument would promote the very high, present interest in the astronomical community to detect and characterize exoplanets. The project successfully passed the conceptual design review (CoDR) in 2019. The instrument is composed of a near-UV band spectrograph (UVS) and a visible band spectrograph (VIS). They provide a spectral resolving power of R ≥100,000 in the visible band (420 nm – 780 nm), and R≥25,000 in the UV band (310 nm – 420 nm). The VIS subsystem will be enclosed in an ultra-stable environment in the Coudé room for the stellar precise radial velocity (PRV) measurements. T he UVS subsystem will be located near the Nasmyth focus to improve the total throughput at the wavelength shorter than 400 nm, to ensure various additional science cases ranging from stellar evolution to the measurement of fundamental constants. This paper gives an overview of the project background, science cases, and technical considerations during the conceptual design phase."
Solar cells operating in harsh conditions such as extraterrestrial environment suffer from ionizing UV irradiation from the sun and radiation damages from high-energy particles. Titania (TiO2) can achieve high transmittance in the visible and near-infrared while efficiently blocking UV irradiations. Cerium-doped yttrium aluminum garnet (YAG:Ce) is commercially used as an efficient spectral downconverter in white-light LEDs, and it has also been studied for its potential as a radiation-withstanding scintillator. We propose TiO2 / YAG : Ce thin films utilizing TiO2’s UV cut-off properties as well as YAG:Ce’s downshifting properties as both multipurpose protector and performance enhancer for solar cells.
When a multimode fiber transmits a laser beam, the speckle will form in its output field. A dynamic fiber scrambler
could be used to suppress the speckle. No matter what actual way of suppressing speckle is, such as fiber scrambling or
using a rotating phase plate, the suppression is the result of exerting disturbance in the process of the speckle forming.
We could disturb the phase of the input beam with specific method to weaken the speckle effect. To get a speckle image
formed by a multimode fiber, we simulate different diffraction patterns under different phase conditions using diffraction
model, in which the phase of the input beam is modulated by a rough surface, and then sum them to form the
instantaneous speckle. To study the speckle suppression, we superpose instantaneous speckles, and as a consequence the
final speckle is suppressed. The simulation would help us understand the speckle suppression experiment with the input
beam phase modulation conducted in our lab.
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