Abstract:A coherent-mode representation for spatially and spectrally partially coherent pulses is derived both in the space-frequency domain and in the space-time domain. It is shown that both the cross-spectral density and the mutual coherence function of partially coherent pulses can be expressed as a sum of spatially and spectrally and temporally completely coherent modes. The concept of the effective degree of coherence for nonstationary fields is introduced. As an application of the theory, the propagation of Gaus… Show more
“…This result differs from other reported works [17][18][19] in that the whole train of pulses is considered rather than assuming that each pulse is incoherent with all other pulses. The spectral density [19] of the pulsed beam as a function of frequency and position is defined to be…”
Section: Modulation and Propagationcontrasting
confidence: 85%
“…The theoretical study of non-stationary statistical optics, applied to pulse trains, has seen a recent resurgence [17][18][19][20]. In the model presented in these references, a restricted class of non-stationary fields is considered in which a stationary field is modulated in a deterministic fashion -this is known as an intrinsically stationary model [21].…”
The problem of predicting and interpreting the results of interferometric optical experiments involving pulse trains is addressed. Specifically, a cyclostationary field arising from the modulation of a stationary, stochastic source is considered in the classical Young's experiment. It is shown that the effects of modulation may be identical to unrelated statistical interference effects.
“…This result differs from other reported works [17][18][19] in that the whole train of pulses is considered rather than assuming that each pulse is incoherent with all other pulses. The spectral density [19] of the pulsed beam as a function of frequency and position is defined to be…”
Section: Modulation and Propagationcontrasting
confidence: 85%
“…The theoretical study of non-stationary statistical optics, applied to pulse trains, has seen a recent resurgence [17][18][19][20]. In the model presented in these references, a restricted class of non-stationary fields is considered in which a stationary field is modulated in a deterministic fashion -this is known as an intrinsically stationary model [21].…”
The problem of predicting and interpreting the results of interferometric optical experiments involving pulse trains is addressed. Specifically, a cyclostationary field arising from the modulation of a stationary, stochastic source is considered in the classical Young's experiment. It is shown that the effects of modulation may be identical to unrelated statistical interference effects.
“…To describe FEL statistical pulse properties with a simple model we considered that the FEL beam spectral crosscorrelation function can be characterized in the framework of the Gaussian Schell model (GSM) [48] …”
Section: Theoretical Principles Of Intensity-intensity Interferommentioning
We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation.
“…The global degree of coherence for scalar waves [36][37][38][39][40] has been translated to the vectorial case in Ref. 22 in terms of the spatial weighted average of the square of the local degree of coherence for vectorial fields ͑r 1 , r 2 ͒ in Eq.…”
We assess the degree of coherence of vectorial electromagnetic fields in the space-frequency domain as the distance between the cross-spectral density matrix and the identity matrix representing completely incoherent light. This definition is compared with previous approaches. It is shown that this distance provides an upper bound for the degree of coherence and visibility for any pair of scalar waves obtained by linear combinations of the original fields. This same approach emerges when applying a previous definition of global coherence to a Young interferometer.
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