Stage Of Laser Irradiation Research Articles

Research on Charge Transfer Characteristics Induced by Laser Irradiation Monocrystalline Silicon

In order to study the charge characteristics of monocrystalline silicon irradiated by femtosecond pulsed laser, measurement systems of charge and infrared temperature induced by femtosecond pulse laser irradiation monocrystalline silicon are established by using oscilloscope and infrared thermal imager. The monocrystalline silicon (circle disc) irradiated by femtosecond pulse laser are carried out along the thickness direction of monocrystalline silicon. The experimental results show that the thermo-mechanical coupling effect of femtosecond pulsed laser irradiated on monocrystalline silicon will produce polarization in the target. At the initial stage of laser irradiation, the laser damage threshold of the interface between crystal surface and air is low and the charge mainly transfers along the surface of monocrystalline silicon, resulting in a high polarization. With the continuation of laser irradiation, it proves that the charge transfers in monocrystalline silicon gradually, and the polarization degree decreases with the modification of the material internal structure. After laser irradiation for a certain time, the charge transfers tend to be stable. Because the target lies in front of the laser focus, its energy density is insufficient to destroy the macrostructure of the target due to laser-pressure and temperature gradient, the polarization effect tends to be stable, resulting in a stable periodic change of charge transfer and recovery.

Picosecond laser fabrication of microchannels inside Foturan glass at CO2 laser irradiation and following etching

In this work, the formation of hollow-type microchannels in the bulk of a photostructurable glass of the brand Foturan is proposed. It is based on the chemical dissolution of crystallized areas, which are formed as a result of the action of picosecond laser pulses and photothermal treatment produced by CO2 laser irradiation. A speed of formation of microchannels was estimated. Microchannels formation features at each stage of laser irradiation are discussed, and the dependence of microchannels characteristics (size, shape and roughness of inner walls) on laser processing and chemical etching parameters were evaluated as well.

Femtosecond-laser hyperdoping silicon in an SF6 atmosphere: Dopant incorporation mechanism

In this paper, we examine the fundamental processes that occur during femtosecond-laser hyperdoping of silicon with a gas-phase dopant precursor. We probe the dopant concentration profile as a function of the number of laser pulses and pressure of the dopant precursor (sulfur hexafluoride). In contrast to previous studies, we show the hyperdoped layer is single crystalline. From the dose dependence on pressure, we conclude that surface adsorbed molecules are the dominant source of the dopant atoms. Using numerical simulation, we estimate the change in flux with increasing number of laser pulses to fit the concentration profiles. We hypothesize that the native oxide plays an important role in setting the surface boundary condition. As a result of the removal of the native oxide by successive laser pulses, dopant incorporation is more efficient during the later stage of laser irradiation.

Microwave-assisted hydrothermal synthesis and temperature sensing application of Er3+/Yb3+ doped NaY(WO4)2 microstructures

Laurustinus shaped NaY(WO4)2 micro-particles assembled by nanosheets were synthesized via a microwave-assisted hydrothermal (MH) route. The growing mechanisms for the obtained resultants with various morphologies were proposed based on the observation of scanning electron microscopic (SEM) images. It was found that Na3Cit added into the reaction solution greatly influenced the formation and size dimension of the nano-sheets, furthermore determined assembling of the laurustinus shaped micro-particles. The temperature sensing performance of NaY(WO4)2:Er3+/Yb3+ was evaluated. Thermal effect induced by the 980nm laser irradiation in laurustinus-shaped NaY(WO4)2:Er3+/Yb3+ phosphor was studied. It was found that the green upconversion luminescence intensity increased in the first stage of laser irradiation, and then decreased after reaching a maximum. Based on the thermal sensing technology the laurustinus NaY(WO4)2:Er3+/Yb3+ microparticles were used as thermal probe to discover thermal effect of upconversion luminescence in laurustinus NaY(WO4)2:Tm3+/Yb3+ micro-particles.

Three-temperature modeling of carrier-phonon interactions in thin GaAs film structures irradiated by picosecond pulse lasers

This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results, it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated. For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser irradiation.

Target density and surface state effects on the compositional changes in iron oxide particle aggregated films prepared by laser ablation

Iron oxide nanoparticle aggregated films were prepared using the excimer laser ablation technique by adopting an off-axis configuration and the gas condensation process. Sintered iron oxide (α-Fe2O3) targets were ablated in oxygen ambient by an ArF excimer laser. The product of ablation comprised Fe2O3 at lower pressure and a mixture of Fe2O3 and FeO at higher pressure by X-ray-diffraction measurements. The maximum ambient oxygen pressure, PS(O2), at which the product composition was still a single Fe2O3 phase was higher for the higher-density target than for its lower-density counterpart. The target surface state affected the product composition only if the pressure was set to the pressure PS(O2) of 40 Pa for a high-density target. When the fluence was high (200 mJ/pulse, 3.3-mm2 spot size), the product composition varied at the initial stage of laser irradiation with the number of laser pulses from a mixture of Fe2O3 and FeO to only Fe2O3 along with the target surface morphological change from a grooved structure to a smooth surface. Product composition was practically independent of the number of pulses by low-fluence laser irradiation even at this particular pressure of 40 Pa.

The analytical study on the laser induced reverse-plugging effect by using the classical elastic plate theory (II)?Reverse-bulge motion

The reverse-bulge motion (RBM) in the metallic foils, which is induced by spatially cylindrical long pulse laser, is examined in order to analyse the newlydiscovered reverse-plugging effect (RPE). An uncoupled, thin plate theory is used to determine the induced flexural vibrations. The solution is obtained as the superposition of two displacement fields, representing the quasi-static and the dynamic behaviors. Meanwhile, the equivalent thermal loading and the dimensionless analysis of thin plate motion are presented. Numerical results presented may partially explain the RBM of thin plate at the early stage of laser irradiation.