Collinear broadband optical parametric generation in periodically poled lithium niobate crystals by group velocity matching

Collinear broadband optical parametric generation (OPG) using periodically poled lithium niobate (PPLN) crystals were designed and experimentally demonstrated with the quasi-phase matching (QPM) periods of 21.5, 24.0, and 27.0 μm. The broad gain bandwidth was accomplished by choosing a specific set of the period and the pump wavelength that allows the group velocities of the signal and the idler to match close to the degeneracy point. OPG gain bandwidth and also the spectral region could be controlled by proper design of QPM period and pump wavelength. The total OPG gain bandwidth of 600, 900, and 1200 nm was observed for the PPLN devices with QPM periods of 21.5, 24.0, and 27.0 μm, respectively. We have also observed multiple color visible generation whenever the OPG spectrum was significantly broad. From the visible peaks of the three PPLN samples, it is found that broad gain bandwidth is crucial in the temperature-insensitive collinear simultaneous RGB generation from a single crystal.     

Aryltriazene photopolymer thin films as sacrificial release layers for laser-assisted forward transfer systems: study of photoablative decomposition and transfer behavior

Thin films of a tailor-made photodecomposible aryltriazene polymer were applied in a modified laser-induced forward transfer (LIFT) process as sacrificial release layers. The photopolymer film acts as an intermediate energy-absorbing dynamic release layer (DRL) that decomposes efficiently into small volatile fragments upon UV laser irradiation. A fast-expanding pressure jet is generated which is used to propel an overlying transfer material from the source target onto a receiver. This DRL-assisted laser direct-write process allows the precise deposition of intact material pixels with micrometer resolution and by single laser pulses. Triazene-based photopolymer DRL donor systems were studied to derive optimum conditions for film thickness and laser fluences necessary for a defined transfer process at the emission wavelength of a XeCl excimer laser (308 nm). Photoablation, surface detachment, delamination and transfer behavior of aryltriazene polymer films with a thickness from 25 nm to ∼400 nm were investigated in order to improve the process control parameters for the fabrication of functional thin-film devices of microdeposited heat- and UV-sensitive materials.     

First-principles investigation of electronic and optical properties in wurtzite Zn<Subscript>1-x</Subscript>Mg<Subscript>x</Subscript>O

A first-principles study has been performed to evaluate the electronic and optical properties of wurtzite Zn_1-xMg_xO. Substitutional doping is considered with Mg concentrations of x = 0, 0.0625, 0.125, 0.1875 and 0.25, respectively. Mg incorporation can induce band gap widening due to the decrease of Zn 4s states. The imaginary part of the dielectric function shows that the optical transition from band edge emission decreases slightly with increasing Mg contents. The optical band gap also increases from 3.2 to 3.7 eV with increasing Mg contents from 0.0625 to 0.25. The calculated results suggest that relatively high Mg concentration is necessary for effective band gap engineering of wurtzite Zn_1-xMg_xO.     

Phase theory for binary one-dimensional Fermi gases in harmonic traps

The phase theory of two interacting one-dimensional degenerate Fermi gases confined to different harmonic traps is developed based on the concept of bosonization. The excitation spectra of mass and composition waves are calculated and stability boundaries as function of interaction strength and frequency detuning of the traps are found. The experimentally accessible non-local mobilities and their relation to the excitation frequencies are also studied. The problem of the Kohn mode within phase theory is discussed and a solution is proposed. As an example of the simplicity and effectiveness of the new approach the propagation of a composition perturbation across the Fermi seas is calculated analytically.     

Ion extraction from the surface ablated materials in electric fields using an intense femtosecond laser pulse

In order to develop a femtosecond laser ablation (fsLA) ion source for TOF mass spectrometry, we have analyzed time-resolved images of laser-induced fluorescence from Sm⁺ ions produced by fsLA of a solid samarium in electric fields. The polarity and the strength of electric fields had a remarkable effect on the expansion of Sm⁺ ions. Moreover, accelerating electric fields elongated the duration of the ion emission from the samarium surface in fsLA, which degraded time-focusing of the ions. We have found that suppression the continuous ion emission caused by fsLA in electric fields is most important in TOF measurements.     

Recurrence spectra and dynamical simulation of Rydberg hydrogen atom near a metal surface

By using the closed-orbit theory including the effect of Coulomb scattering together with an electrical image potential approach, the recurrence spectra and the dynamical behaviours of the Rydberg hydrogen atom near a metal surface are presented. Theoretical analysis and numerical simulation reveal that the impacts of the image potential contributing to the recurrence spectrum are qualitatively analogous to that of the parallel electrical and magnetic fields on the Rydberg atom. The recurrence spectra are computed for a few selected scaled energies and the results demonstrate that the scaled energy dominates the dynamical properties of system. With the increase of the scaled energy e from small to large, the whole trend of spectral structure is from simple to complex,and then simple.     

Microwave specific loss power of magnetic fluids subjected to a static magnetic field

This paper reports on the frequency dependence of the magnetic and electric power dissipation in a magnetic fluid sample, in the microwave frequency range (0.5 to 8GHz), at various values of the static magnetic field (0 to 167.8kA/m). The computation of the power dissipation relies on the experimental values measured for the complex dielectric permittivity, ɛ = ɛ′ - iɛ″, and the complex magnetic permeability, μ = μ′ - iμ″, over the same frequency range. The results show that the magnetic power dissipation is much larger than the electric one for the investigated sample. At a specific frequency, f (Hz) , the power dissipation, p, depends on the external magnetic field, and exhibits a maximum. The result obtained suggests the possibility of controlling the energy absorption in the microwave range by means of the application of an external magnetic field.     

Time-dependent exactly solvable models for quantum computing

A time-dependent periodic Hamiltonian admitting exact solutions is applied to construct a set of universal gates for a quantum computer. The time evolution matrices are obtained in an explicit form and used to construct logic gates for computation. A way of obtaining an entanglement operator is discussed, too. The method is based on transformation of soluble time-independent equations into time-dependent ones by employing a set of special time-dependent transformation operators. The text was submitted by the authors in English.     

Inequivalent quantizations of the rational Calogero model with a Coulomb type interaction

We consider the inequivalent quantizations of a N-body rational Calogero model with a Coulomb type interaction. It is shown that for a certain range of the coupling constants, this system admits a one-parameter family of self-adjoint extensions. We analyze both the bound and scattering state sectors and find novel solutions of this model. We also find the ladder operators for this system, with which the previously found solutions can be constructed.