scholarly journals Measuring and characterizing the line profile of HARPS with a laser frequency comb

2020 ◽  
Vol 645 ◽  
pp. A23
Author(s):  
F. Zhao ◽  
G. Lo Curto ◽  
L. Pasquini ◽  
J. I. González Hernández ◽  
J. R. De Medeiros ◽  
...  

Aims. We study the 2D spectral line profile of the High Accuracy Radial Velocity Planet Searcher (HARPS), measuring its variation with position across the detector and with changing line intensity. The characterization of the line profile and its variations are important for achieving the precision of the wavelength scales of 10−10 or 3.0 cm s−1 necessary to detect Earth-twins in the habitable zone around solar-like stars. Methods. We used a laser frequency comb (LFC) with unresolved and unblended lines to probe the instrument line profile. We injected the LFC light – attenuated by various neutral density filters – into both the object and the reference fibres of HARPS, and we studied the variations of the line profiles with the line intensities. We applied moment analysis to measure the line positions, widths, and skewness as well as to characterize the line profile distortions induced by the spectrograph and detectors. Based on this, we established a model to correct for point spread function distortions by tracking the beam profiles in both fibres. Results. We demonstrate that the line profile varies with the position on the detector and as a function of line intensities. This is consistent with a charge transfer inefficiency effect on the HARPS detector. The estimate of the line position depends critically on the line profile, and therefore a change in the line amplitude effectively changes the measured position of the lines, affecting the stability of the wavelength scale of the instrument. We deduce and apply the correcting functions to re-calibrate and mitigate this effect, reducing it to a level consistent with photon noise.

2014 ◽  
Vol 14 (8) ◽  
pp. 1037-1045 ◽  
Author(s):  
Fei Zhao ◽  
Gang Zhao ◽  
Gaspare Lo Curto ◽  
Hui-Juan Wang ◽  
Yu-Juan Liu ◽  
...  

Science ◽  
2019 ◽  
Vol 363 (6430) ◽  
pp. 965-968 ◽  
Author(s):  
Qi-Fan Yang ◽  
Boqiang Shen ◽  
Heming Wang ◽  
Minh Tran ◽  
Zhewei Zhang ◽  
...  

Determination of laser frequency with high resolution under continuous and abrupt tuning conditions is important for sensing, spectroscopy, and communications. We show that a single microresonator provides rapid and broadband measurement of optical frequencies with a relative frequency precision comparable to that of conventional dual-frequency comb systems. Dual-locked counterpropagating solitons having slightly different repetition rates were used to implement a vernier spectrometer, which enabled characterization of laser tuning rates as high as 10 terahertz per second, broadly step-tuned lasers, multiline laser spectra, and molecular absorption lines. Besides providing a considerable technical simplification through the dual-locked solitons and enhanced capability for measurement of arbitrarily tuned sources, our results reveal possibilities for chip-scale spectrometers that exceed the performance of tabletop grating and interferometer-based devices.


2012 ◽  
Vol 8 (S293) ◽  
pp. 407-409 ◽  
Author(s):  
F. Zhao ◽  
G. Lo Curto ◽  
L. Pasquini ◽  
G. Zhao

AbstractHigh precision spectroscopy is one of the most successful methods to detect extra-solar planets. To enable the detection of Earth-like planets in the habitable zone, extremely precise instruments are required. Our lack of knowledge of the instrument line profile, non-linearity and charge transfer efficiency effects in the detector limits the achievable precision of an instrument. We report our studies on the HARPS (High Accuracy Radial- velocity Planet Searcher) line profiles, measured using the unresolved lines of a Laser Frequency Comb (LFC). We show how the line profile changes as a function of position and signal, and estimate the errors made in the line centroid measurement due to the variation of the line profile.


2017 ◽  
Vol 25 (14) ◽  
pp. 15890 ◽  
Author(s):  
Govind Vedala ◽  
Mustafa Al-Qadi ◽  
Maurice O’Sullivan ◽  
John Cartledge ◽  
Rongqing Hui

Author(s):  
Frank U. Grupp ◽  
Liang Wang ◽  
Hanna Kellermann ◽  
Ralf Bender ◽  
Ulrich Hopp

2016 ◽  
Vol 10 (4) ◽  
pp. 623-630 ◽  
Author(s):  
Francesco Cappelli ◽  
Giulio Campo ◽  
Iacopo Galli ◽  
Giovanni Giusfredi ◽  
Saverio Bartalini ◽  
...  

Author(s):  
N. David Theodore ◽  
Leslie H. Allen ◽  
C. Barry Carter ◽  
James W. Mayer

Metal/polysilicon investigations contribute to an understanding of issues relevant to the stability of electrical contacts in semiconductor devices. These investigations also contribute to an understanding of Si lateral solid-phase epitactic growth. Metals such as Au, Al and Ag form eutectics with Si. reactions in these metal/polysilicon systems lead to the formation of large-grain silicon. Of these systems, the Al/polysilicon system has been most extensively studied. In this study, the behavior upon thermal annealing of Au/polysilicon bilayers is investigated using cross-section transmission electron microscopy (XTEM). The unique feature of this system is that silicon grain-growth occurs at particularly low temperatures ∽300°C).Gold/polysilicon bilayers were fabricated on thermally oxidized single-crystal silicon substrates. Lowpressure chemical vapor deposition (LPCVD) at 620°C was used to obtain 100 to 400 nm polysilicon films. The surface of the polysilicon was cleaned with a buffered hydrofluoric acid solution. Gold was then thermally evaporated onto the samples.


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