Spectral fitting method for obtaining the refractive index and thickness of chalcogenide films

In this paper, we are dedicated to exemplifying a two parameter curve fitting method and developing a Matlab-based simulation program to extract the nonlinear refractive index and nonlinear absorption coefficient from closed-aperture Z-scan or R(z) data without the need for performing open-aperture Z-scan measurement. It should be noted, however, that both approaches can only be applicable to a case for which the on-axis phase shift at the focus is small. In this way, we not only determine the nonlinear parameters quickly with reasonable accuracy, as well as save time, efforts and equipment in the process of Z-scan implementation, but also obtain an initial estimate in order to compare with the results of the open-aperture Z-scan measurement when needed.

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Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

10.5194/gi-2018-19 ◽

2018 ◽

Author(s):

Joshua M. Chadney ◽

Daniel K. Whiter

Keyword(s):

Water Vapour ◽

Atmospheric Parameter ◽

Atmospheric Parameters ◽

Atmospheric Water ◽

Echelle Spectrograph ◽

Atmospheric Water Vapour ◽

Spectral Fitting ◽

Fitting Method ◽

Airglow Emissions ◽

High Throughput Imaging

Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725–740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES), located on Svalbard. In this paper, we describe our new method and show the results of Monte-Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method as well as provide an indication of uncertainties on the retrieval of each atmospheric parameter.

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Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Geoscientific Instrumentation Methods and Data Systems ◽

10.5194/gi-7-317-2018 ◽

2018 ◽

Vol 7 (4) ◽

pp. 317-329 ◽

Cited By ~ 2

Author(s):

Joshua M. Chadney ◽

Daniel K. Whiter

Keyword(s):

Water Vapour ◽

Atmospheric Parameter ◽

Atmospheric Parameters ◽

Atmospheric Water ◽

Echelle Spectrograph ◽

Atmospheric Water Vapour ◽

Spectral Fitting ◽

Fitting Method ◽

Airglow Emissions ◽

High Throughput Imaging

Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725 and 740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. In this paper, we describe our new method and show the results of Monte Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method and provide an indication of uncertainties on the retrieval of each atmospheric parameter. We show that the method allows for the retrieval of OH temperatures with an uncertainty of 6 % when contamination by N2 emission is small. N2 temperatures can be retrieved with uncertainties down to 3 %–5 % when N2 emission intensity is high. We can determine the intensity ratio between the O+ doublets at 732 and 733 nm (which is a function of temperature) with an uncertainty of 5 %.

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