Interaction and fusion of light pulses at the dynamical four-wave mixing in photorefractive media
All-optical control of impulse parameters is realized via a dynamical transmission four-wave mixing. We show that the nonlinear system, which includes both coupled wave equations and an evolution equation for the dynamical grating amplitude, contains soliton-like solution for the intensity pattern formed in the medium. The nonlocality of the nonlinear response is the main important requirement to the soliton-like solution is established during the wave-mixing process. On some determined conditions the convergence of input pulses into one pulse takes place (i.e. the merge of the solitons) that lead to the dramatic changes of the output pulse shapes and intensities. The precise conditions, when the impulse output can be driven by another guiding pulse are obtained and discussed.
Analytic Structure of the Four-Wave Mixing Model in Photoreactive Material
In order to later find explicit analytic solutions, we investigate the singularity structure of a fundamental model of nonlinear optics, the four-wave mixing model in one space variable z. This structure is quite similar, and this is not a surprise, to that of the cubic complex Ginzburg-Landau equation. The main result is that, in order to be single valued, time-dependent solutions should depend on the space-time coordinates through the reduced variable xi=\sqrt{z} exp(-t / tau), in which tau is the relaxation time.
Portable Computing in Psychiatry
Personal digital assistants (PDAs) or handheld computers have become more popular in the practice of medicine. These devices have implications for psychiatric practice, and this paper reviews various published articles describing their use. The literature demonstrates their use in document editing, patient tracking, accessing medical information and drug reference guides, prescription writing, and medical education. Security on these devices is covered, and the value and increasing implementation of PDAs in psychiatry is discussed.