Interferogram distribution

Figure Bl.2.7. Time domain and frequency domain representations of several interferograms. (a) Single frequency, (b) two frequencies, one of which is 1.2 times greater than the other, (c) same as (b), except the high frequency component has only half the amplitude and (d) Gaussian distribution of frequencies.

Fig. 8.4. Interferogram (left) and radial electron density distribution (right) for a plasma obtained with a ASE-like laser pulse, from [41]. The arrow and the horizontal line in the interferogram indicate the focus position and the 3 mm gas-jet slit position, respectively...

We have recorded the visibility for a series of interferograms at different gas pressures and we observe the expected exponential decay. A good quantitative agreement with decoherence theory is obtained after taking into account the details of the velocity selection in our experiment. For example our predictions for the visibility are obtained by weighting Eq. (7) with the classical velocity distribution in the detector - which corresponds to an averaging over... 

In order to imderstand this important property of Fourier transform spectroscopy, let us consider a broad spectrum over a wide wave number range with one narrow absorption line in it (cf. Fig. 12). Then, according to the rules of Fourier transformation, the broad spectrum produces an interferogram with highly damped oscillation. The maximum amplitude of the oscillation and also the mean value of the interferogram are equal to the total intensity or to the area under the spectral distribution [see Appdx 1 and Eqs. (A 1.1) and (A 1.2)] ... 

Figures.11 (left) shows the reduced distribution of the fit of the real interfero-gram with the simulated interferogram for different cut-off wavenumbers. It can be observed that a minimum peak appears around 20 cm Figure3.11 (right) presents...

Fig. 3.11 Reduced distribution of the fit of the real interferogram with the simulated inter-ferogram for different cut-off wavenumbers (left). Real interferogram (black) and the computed one (W e) when a 21 cm filter is introduced (n gto). The weight coefficients are ci = 1.07 and C2 = 0.45...

To add the photon noise contribution to the interferograms generated by the simulator, Igraw, the dominant term of the NEP considered is the shot noise. In this situation, photon noise follows Poisson statistics and it can be approximated by a Gaussian probability distribution. The generation-recombination contribution to the NEP is assumed to follow also Poisson statistics. The total NEP is calculated as... 

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