The chaotic behavior of on external-cavity semiconductor laser (ECSL) working in a regime of low-frequency
fluctuations (LFFs) can be controlled by external electro-optical phase or intensity current modulation. It is shown by
numerical simulation that, for specific values of the modulating frequency and amplitude, the phase difference between
the laser power drop-out and the modulator remains constant in time leading to phase-synchronized states, steady LFFs,
so called m:n phase synchronization. The degree of stabilization is determined by calculating Shannon's entropy and by
the analyzing the stability of the phase locking. The synchronization regions are mapped and zones of low and high
amplitude chaos are identified. The light emission can be stabilized from a regime of large amplitude chaotic oscillations
corresponding to LFFs to one of low-amplitude chaotic or even periodic oscillations. The dynamics of the laser can be
controlled when the period of the modulating signal is comparable with the laser itinerancy time between consecutive
external-cavity modes.
We present proof-of-principle results regarding the possibility of micro-engraving Potassium Dihydrogen Phosphate (KDP) crystals using laser ablation techniques. The results of the work show that this technique can be used for realizing integrated optics and micro-optics components that are based on such crystals, one of the envisaged directions being that of integrated electro-optical modulators.
In optical field analysis, like restoration of optical phase from phase-modulated images, data acquisition is the primary step in practical reconstruction algorithm. The relation between the experimental sampling rate and the sampling rate request by a particular algorithm is very important. A prior knowledge of the field characteristics cannot be ever done. In this paper we present a self-consistence criterion, based on Wittaker-Shannon theorem, for fields reconstruction algorithms. The criterion correlate the energy of the output database using primary data acquisition with the energy of a database obtained by sub-sampling initial data and can increase the confidence in the result of a reconstruction algorithm applied to a specific input field. We apply the criterion to validate the phase restoration of a following- pass, inverse cosine transform algorithm.
Using a numerical code assisted data processing we show that the precision in the ellipsometric type measurements can be improved with a sufficient degree of confidence, up to an order of magnitude. Our method is based on fitting the experimental data with a pari of functions of known theoretical behavior. Essentially, we corroborate the result obtained from one strongly nonlinear function to those given by another behaving 'ultra-linearly'. When working with consistent experimental data, this procedure leads to a pair of 'outputs' that enhance one another producing an increased degree of precision. The paper explicitly applies this idea to an ellipsometric type measurement for the refraction index of a glass specimen.
A method for local thermodynamic equilibrium plasma diagnostics by vibrational structure of diatomic molecule electronic states is elaborated. On this purpose is adopted a model of plasma temperature determination from the relative intensities of the molecular vibrational band head incompletely spectrally resolved. The relative intensities were determined using the temporal integrated profile instead of peak or integrated spectral profile of a band head. This more accurate method of vibrational temperature determination allows obtained new data about the plasma internal processes.
This paper presents a method to retrieve the relative phase of an optical field starting from three digitized intensity records. One record is that of the classical intensity of the field itself, while the second and the third are intensities obtained after some filtering operations performed in the Fourier space of the optical field. The paper also gives several applications of the algorithm to both 1D and 2D cases.
Mixed valence ion doped polymers are potential materials for the real time holography. We review the intimate mechanisms imposing suitable optical properties in Fe:PVA, stressing on the main role played by the Fe ions. Under the UV exposure, both the refractive index and the absorption coefficient are changing due to a local electron transfer from the PVA matrix to the Fe3+ ions. The absorption coefficient proved to be dependent on a new-formed low spin Fe2+ state whereas the refractive index and the absorption coefficient are changing due to a local electron transfer from the PVA matrix to the Fe3+ ions. The absorption coefficient proved to be dependent on a new-formed low spin Fe2+ state whereas the refractive index is related to the total content of the high spin Fe2+ state. The diffraction efficiency data are explained in terms of the Fe2+/Fe3+ ratio. Additional data concerning the electron transfer in Sn:PVA thin films are also discussed.
The molecular vibration temperature of the plasma from an interrupt arc discharge in air at atmospheric pressure and at current intensities in the range of 2 divided by 8 Amperes, using electronic and vibration bands of violet [B2(Sigma) + - X2(Sigma) +] and red [A2(Pi) - X2(Sigma) +] systems of the CN molecule was determined. At the equilibrium temperature of 6400 K, 27 lines of Ti, contained as impurity in coal electrode were found. These spectral lines were found in the 247 divided by 340 nm spectral range, having the upper levels of the excitation energies in the 3.60 divided by 5.69 eV range, in the neighborhood of the energy of dissociation of the CN molecule on the fundamental electronic state. Some considerations about the vibrational states populations are also made.
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