Noncollinearity limit

Although there are no slits associated with an AOTF device, there are some necessary compromises regarding throughput. First, there are physical restrictions on the size of available crystals, and in the case of the normal noncollinear arrangement where the inpnt beam direction is traversed by the acoustic wave front, then the open beam apertnre needs to be limited so that the transit time of the aconstic wave front across the crystal is limited, in order that a narrow optical band pass can be maintained. Typically this is of the order of a few millimeters. 

Transform-limited (TL) visible pulses with as short as sub-5-fs duration have been generated from a noncollinear optical parametric amplifier and applied to the study of polyacetylene, polydiacetylene, azobenzene, and J-aggregates of porphyrin for optical -devices. 

Transform-limited (TL) visible pulses with as short as 3.9 and 4.7-fs duration have been generated from noncollinear optical parametric amplifiers (NOPA)[l-7], and they were applied to the study of various systems [8-14], We reported several new phenomena the direct observation of transition state during photochemical reaction by probing the change in the electronic transition probability induced by nuclear motion. In this paper four subjects are discussed. They are (1) NOPA, (2) polyacetylene, (3) polydiacetylene and (4) bacteriorhodopsin. 

Experiments were performed using a visible optical parametric amplifier based on noncollinear phase-matching in /3-barium borate, followed by a pulse compressor using chirped dielectric mirrors. This optical source provides ultrabroadband pulses, with bandwidth extending from 500 to 720 nm, compressed to an almost transform-limited duration of 5-6 fs. The pump-... 

In conclusion, the self-consistent PF model is a powerful tool for the analysis of a large variety of long-period magnetic structures, collinear (antiphase, amplitude-modulated) as well as noncollinear (helix, fan,. ..). In the examples presented above this model is limited to single-g (and obviously to its harmonics and 2=0) systems but it can be extended without problem to the case of multi-g systems. 

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