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- Kröll, Stefan, et al.
(author)
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Influence of laser mode amplitude and laser mode phase fluctuations on spectral noise in CARS
- 1989
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In: Quantum Electron Laser Sci Conf. ; , s. 92-92
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Conference paper (peer-reviewed)abstract
- A model for calculating the noise in nonlinear optical processes arising from (nonquantum) stochastic fluctuations (mode beating) in and between the lasers participating in the nonlinear interaction has been previously developed. Assuming that all individual laser mode phases and laser modes are (statistically) independent (Gaussian statistics) and that the nonlinear interaction can be expressed as a perturbation expansion in the participating fields, deterministic expressions for the expected intensity and higher order moments for the signal were obtained in a straightforward way. The authors have explicitly evaluated the deterministic expressions, obtaining closed-form expressions for the SNR in coherent anti-Stokes Raman scattering (CARS) as a function of laser mode spacing, laser and Raman bandwidths and the duration of the anti-Stokes pulse. Those results qualitatively agreed with their experimental results. The theoretical analysis further indicates that the (nonquantum) noise in nonlinear optical processes from multimode lasers can be separated into terms (explicitly evaluated) arising from shot-to-shot fluctuations in the laser mode amplitudes and terms arising from shot-to-shot fluctuations in the individual laser mode phases.
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- Kröll, Stefan, et al.
(author)
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Noise characteristics of single shot broadband Raman-resonant CARS with single- and multimode lasers
- 1987
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In: Applied Optics. - 2155-3165. ; 26:6, s. 1068-1073
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Journal article (peer-reviewed)abstract
- A simple model is presented as an aid in understanding, first, the relative noise performance and, second, the noise reduction achievable by referencing, in different experimental approaches to single shot broadband coherent anti-Stokes Raman scattering (CARS). Qualitative agreement is obtained with previous experimental investigations of CARS noise. The broadband dye laser radiation is described as the sum of independent modes with random phases. The dye laser contribution to the CARS noise is then approximately inversely proportional to the square root of the number of dye laser modes generating the detected signal. A fundamental idea is that in Raman resonant spectra only the number of Stokes modes actually participating in driving the Raman resonance should be counted. This means, e.g., that for narrow Raman resonances, as in an atmospheric flame, the noise generated by the dye laser will be higher for a single-mode pump laser than for a multimode pump laser with the experimental CARS configuration normally employed. The implications of the model for the dual broadband type CARS techniques are also discussed.
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- Kröll, Stefan, et al.
(author)
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Time-resolved laser spectroscopy on high-lying states in neutral oxygen
- 1985
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In: Physical Review Letters. - 1079-7114. ; 55:3, s. 284-287
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Journal article (peer-reviewed)abstract
- Radiative lifetimes have been measured for five triplet states of atomic oxygen. The oxygen atoms were generated by photodissociation of NO2 and the investigated states were populated through a two-step process involving a two-photon excitation to the lowest excited triplet state of even parity, 2p33p 3P, followed by a one-photon excitation to the investigated state. A similar scheme is applicable to the study of excited states in many light atoms.
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