Effect Of Intense Laser Radiation Research Articles

Hot Carrier Effects on Real and Imaginary Parts of Brillouin Susceptibilities of Magnetoactive Doped III-V Semiconductors (Applied to N-type Doped InSb)

An analytical investigation is made of hot carrier effects on real and imaginary parts of Brillouin susceptibility ( ) of magnetoactive doped III-V semiconductors. Coupled mode approach is used to obtain expressions for . Numerical calculations are made for n-InSb crystal −CO2 laser system. Efforts are made to obtain enhanced values of and change of their sign under appropriate selection of external magnetic field (B0) and doping concentration (n0). The hot carrier effects of intense laser radiation modifies the momentum transfer collision frequency of carriers and consequently the nonlinearity of the medium, which in turn (i) further enhances , (ii) shifts the enhanced towards smaller values of B0, and (iii) widens the range of B0 at which change of sign of occurs. The change of sign of enhanced of magnetoactive doped III-V semiconductors, validates the possibility of chosen Brillouin medium as a potential candidate material for the fabrication of stimulated Brillouin scattering dependent widely tunable and efficient optoelectronic devices such as optical switches and frequency converters.
 HIGHLIGHTS
 
 Hot carrier effects of intense laser radiation
 
 enhances real and imaginary parts of Brillouin susceptibility,
 shifts the enhanced real and imaginary parts of Brillouin susceptibility towards smaller values of magnetostatic field,
 widens the range of magnetostatic field at which change of sign of real and imaginary parts of Brillouin susceptibility occurs
 
 
 Analysis offer three achievable resonance conditions at which significant enhancement as well as change of sign of real and imaginary parts of Brillouin susceptibility are obtained
 Analysis establishes the technological potentiality of III-V semiconductors as hosts for fabrication of SBS based widely tunable and efficient optoelectronic devices
 
 GRAPHICAL ABSTRACT

Thermophysical and spectral features of laser ablation of polymers

The effect of intense laser radiation on polymers depends on many factors; the most important of these factors are the optical properties of the polymer at the emission wavelength and the irradiation mode (continuous or pulsed). In the case of ablation of polytetrafluoroethylene (PTFE) with continuous CO2 laser radiation at a wavelength of 10.6 μm, the initial target temperature and the state of the target microstructure, which is determined by the polymer monolithization mode, are also influencing factors. An increase in the initial temperature of a PTFE target from room temperature to 683 K provides a 2.8-fold increase in the ablation rate and a significant increase in the fiber fraction yield, the quantitative values of which depend on the polymer synthesis and monolithization modes. A tenfold decrease in the emission wavelength to 1.06 μm leads to a multifold decrease in the ablation efficiency of radiation for all polymers; the multiplicity of change in the ablation rate compared to that on a CO2 laser depends on the polymer type.

Effect of Optical Radiation on the Properties of Gamma Radiated Silicate Glass

We study the effect of intense laser radiation on the surface of silicate glass prior irradiated by gamma radiation. Experimental results show that the gamma radiation with dose 5 × 104 R leads to the degradation of the surface resistance of this optical dielectric to electromagnetic radiation. Depending on the dose of the radiation the laser radiation can result in either surface erosion or its pronounced cracking. It is also found that the efficiency of the degradation process is determined not only by the radiation dose, but also by the presence of different impurities in the glass.

Electron-related nonlinearities in GaAs–Ga1−xAlxAs double quantum wells under the effects of intense laser field and applied electric field

The combined effects of intense laser radiation and applied electric fields on the intersubband-related linear and nonlinear optical properties in GaAs-based quantum wells are discussed. It is shown that for asymmetric double quantum well, the increasing laser field intensity causes progressive redshifts in the peak positions of the second and third harmonic coefficients. However, the resonant peaks of the nonlinear optical rectification can suffer a blueshift or a redshift, depending on the laser strengths. The same feature appears in the case of the resonant peaks corresponding to the total coefficients of optical absorption and relative change in the refractive index.

Study of direct and indirect exciton states in GaAs-Ga1−xAlxAs quantum dots under the effects of intense laser field and applied electric field

The effects of intense laser radiation on the exciton states in GaAs-Ga1�xAlxAs quantum dots are studied with the inclusion of applied dc electric fields oriented along the growth direction of the system. The calculations are made within the effective mass and parabolic band approximations. The intense laser effects have been included along the lines of the Floquet method, modifying the confinement potential associated to the heterostructure. The laser field modifies the Coulomb potential via the generation of two interaction centers. The exciton binding energy behaves as a decreasing function of the laser field strength, as well as of the size of the quantum dot. The normalized photoluminescence peak energy increases with the laser field strength and behaves as a decreasing function of the dot's dimensions for fixed laser field intensity.

Combined effects of intense laser field and applied electric field on exciton states in GaAs quantum wells: Transition from the single to double quantum well

AbstractThe effects of intense laser radiation on the exciton states in GaAs‐Ga1–xAlxAs quantum wells are studied with the inclusion of applied dc electric fields oriented along the growth direction of the system. The calculations are made within the effective mass and parabolic band approximations. The intense laser effects have been included along the lines of the Floquet method, modifying the confinement potential associated to the heterostructure. The results for the exciton binding energy, the energy of the exciton‐related photoluminescence peak, and the carriers overlap integral are presented for several configurations of the quantum well size, the strength of the applied electric fields, and the incident laser radiation.

Intense laser effects on donor impurity in a cylindrical single and vertically coupled quantum dots under combined effects of hydrostatic pressure and applied electric field

Using the effective mass and parabolic band approximations and a variational procedure we have calculated the combined effects of intense laser radiation, hydrostatic pressure, and applied electric field on shallow-donor impurity confined in cylindrical-shaped single and double GaAs–Ga 1− x Al x As QD. Several impurity positions and inputs of the heterostructure dimensions, hydrostatic pressure, and applied electric field have been considered. The laser effects have been introduced by a perturbative scheme in which the Coulomb and the barrier potentials are modified to obtain dressed potentials. Our findings suggest that (1) for on-center impurities in single QD the binding energy is a decreasing function of the dressing parameter and for small dot dimensions of the structures (lengths and radius) the binding energy is more sensitive to the dressing parameter, (2) the binding energy is an increasing/decreasing function of the hydrostatic pressure/applied electric field, (3) the effects of the intense laser field and applied electric field on the binding energy are dominant over the hydrostatic pressure effects, (4) in vertically coupled QD the binding energy for donor impurity located in the barrier region is smaller than for impurities in the well regions and can be strongly modified by the laser radiation, and finally (5) in asymmetrical double QD heterostructures the binding energy as a function of the impurity positions follows a similar behavior to the observed for the amplitude of probability of the noncorrelated electron wave function.

Effect of intense laser radiation on controlled VO2 mirrors

Effect of intense laser radiation on controlled VO2 mirrors

Quantum mechanical theory of collisional ionization in the presence of intense laser radiation

We present a quantum-mechanical formalism for treating ionizing collisions occurring in the presence of an intense laser field. The theory rigorously takes into account both the intense laser radiation and the internal electronic continuum states associated with the emitted electrons. We accomplish this essentially by combining discretization techniques, used in a recent study of fieldfree collisional ionization, with expansions in terms of so-called electronic-field representations for the quasi-molecule-plus-photon system. This leads to a coupled-channel description of the heavy-particle dynamics which involves effective electronic-field potential surfaces and continua. We also discuss qualitatively characteristic features of ionizing collisions accompanied by intense lasers, drawing comparisons with their fieldfree counterparts. Our remarks are designed to encourage experimental investigation of collisional ionization in the presence of intense lasers, and to stimulate further theoretical work. Because the electronic continuum meets requirements of exact energy resonance for absorption of a photon over large ranges of the internuclear separations, collisional ionization in an intense field should occur much more readily than other field-influenced inelastic collisions, in which photon absorption is resonant only near potential surface pseudocrossings. We therefore suggest laser-influenced ionizing collisions as very good candidates for experimental verification of the effects of intense laser radiation on inelastic collisional processes. We describe the anticipated behavior of the energy distribution of electrons emitted due to radiative coupling. Our comments are based on some physically reasonable assumptions about the electronic transition dipole matrix elements between discrete and continuum electronic states. Actual calculations of such matrix elements involve special electronic structure considerations, and these are outlined in some detail in an Appendix.