Simultaneous design of power stage and controller for switchingpower supplies

This paper develops a method for simultaneously designing the power stage and controller for a switching power supply. The method utilizes a numerical optimization procedure, which facilitates computer-aided design. It is found that better performance can be achieved than with a traditional two-step design process, where the power stage and controller are designed sequentially. Optimization and simulation results for a buck power converter are presented to illustrate the design process and benefits     

Passively Q-switched solid-state lasers with intracavity opticalparametric oscillators

A rate-equation-based model that describes the behavior of a passively Q-switched solid-state laser containing an intracavity optical parametric oscillator (OPO) is developed. In such a laser there is no output at the fundamental or pump wavelength. When the OPO signal field begins to build up, it acts as a loss for the pump and thus cavity dumps the pump resonator. The model developed explains this behavior and enables one to select OPO parameters which optimize the system's performance. Application of the model to a compact, lightweight, eye-safe, laser range finder operating at 1.54 μm is also described     

The role of the pion cloud in the interpretation of the valence light-cone wavefunction of the nucleon

The pion cloud renormalises the light-cone wavefunction of the nucleon which is measured in hard, exclusive photon-nucleon reactions. We discuss the leading twist contributions to high-energy exclusive reactions taking into account both the pion cloud and perturbative QCD physics. The nucleon’s electromagnetic form-factor at high Q² is proportional to the bare nucleon probability Z and the cross-sections for hard (real at large angle or deeply virtual) Compton scattering are proportional to Z². Our present knowledge of the pion-nucleon system is consistent with Z = 0.7 ± 0.2. If we apply just perturbative QCD to extract a light-cone wavefunction directly from these hard exclusive cross-sections, then the light-cone wavefunction that we extract measures the three valence quarks partially screened by the pion cloud of the nucleon. We discuss how this pion cloud renormalisation effect might be understood at the quark level in terms of the (in-)stability of the perturbative Dirac vacuum in low energy QCD.     

A new technique for spatially resolved thermal lensing measurements

A new method is presented for spatially resolved thermal lensing measurements using multiple narrow probe beams and a two-dimensional array detector. The method is applied to an Er, Tm, Ho: YAG laser rod. No significant deviation from a parabolic temperature profile has been found although there is extraordinarily strong thermal lensing in the crystal. Thermo-optical constants of the material are reported.     

Properties of diode laser pumps for high-power solid-state lasers

Diode lasers used to pump high average power solid-state lasers typically have broad spectral width so that most of the pump light is not at the peak of the gain medium's absorption feature. However, the long absorption length in these lasers enables even weakly absorbed light to pump efficiently. The result is that high absorption efficiency and improved pump distribution uniformity are possible when using realistic pump diodes. In addition, both quantities are nearly independent of the pump center wavelength.     

High-brightness white-light source based on up-conversion phosphors

We report the implementation of a new, high brightness, high efficiency white-light source based on up-conversion phosphors. Up-conversion materials absorb near infrared light and re-emit in red, green, and blue. It is possible to combine these colors to create a white-light source. Such a source has the same appealing characteristics as those reported for up-conversion displays: very high brightness operation without damage to the emitters, long lifetimes, and efficiencies comparable to those of existing technologies. In addition, they offer simplicity of fabrication and a variety of operating modes. Here we demonstrate a 7-lm/W D65 white light emitter yielding 2 kcd/m/sup 2/ on a simple diffuser.     

(α-Nitroalkyl)-ONN-azoxysulfones and some of their transformations

A regioselective method for the synthesis of [(-nitroalkyl)-ONN-azoxy]alkyl- and-arylsulfones by oxidative condensation of pseudonitroles with aliphatic and aromatic sulfamides under the action of dibromoisocyanurate (DBI) was proposed. The behavior of the azoxysulfones obtained toward acids and bases as well as futher transformations of the products of acid hydrolysis into salts and halo-derivatives of nitroalkylazoxysulfones were investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1267–1270, July, 1994.