Interference effects in femtosecond spectroscopy

Abstract

This article aims to provide a short synopsis of interference effects connected with ultrafast laser pulses, where 'ultrafast' is defined as ca. 100 fs or faster. The discussion is divided into three parts: the first shows how interference between waves is responsible for generation of light pulses in the femtosecond and attosecond time domains; the second describes characterization of ultrafast pulses by different interferometric techniques, including diffraction of femtosecond light by a double slit; and the final section discusses selected measurements of interference phenomena created and probed with femtosecond time resolution, with an emphasis on experiments in atomic physics. The article attempts to illustrate how wave-like interference is a unifying concept that pervades much of physics on a femtosecond time-scale.

Coherent Energy Transfer under Incoherent Light Conditions

“…13 This is not the case because even if one could decompose sunlight as a collection of, for example, femtosecond coherent pulses, the temporal coherence associated with the ensemble is short, on the order of only 1 fs. 31 The formalism we have presented above allows for a description of the excitation process under continuous illumination with a collection of photoexcitation and deexcitation events, leading to steady-state dynamics. This carries with itself a statistical average of all possible absorptions (and emissions) of a photon at different energies and different instants of time.…”

“…In such a case the radiation field creates a superposition of exciton states after the absorption of a single photon, thereby imprinting its correlations on the excited molecular state. , It was previously suggested that sunlight could be regarded as a series of random ultrashort spikes and as such sunlight would create a coherent superposition of states . This is not the case because even if one could decompose sunlight as a collection of, for example, femtosecond coherent pulses, the temporal coherence associated with the ensemble is short, on the order of only 1 fs …”

Experimental Coherent Laser Control of Physicochemical Processes

“…The accelerated progress and the very exciting successes in this field have increased the demand for reviews. During the past few years, a number of reviews have been written on coherent control, the majority of them emphasizing theoretical concepts rather than experimental implementation. − This review takes a different approach. Instead of focusing on the theory, we focus on the experiments, their requirements, the signals, and their interpretation.…”