Soft x-ray Ar laser excited by low-voltage capillary discharge.

We demonstrated the operation of a 46.9-nm capillary discharge Ar -laser excited by electrical pulses at a very low voltage (35 - 45 kV), which is approximately two times lower than previously reported. The decrease in pulse voltage not only allows for further reduction in the size of the laser's excitation part, but also a principal shift to the experimental methods, techniques, and technologies used in ordinary pulsed gas lasers operating in the ultraviolet, visible, and infrared regions of the spectra.

Magnetoelectric confinement and stabilization of Z pinch in a soft-x-ray Ar(+8) laser.

Magnetoelectric confinement and stabilization of the plasma column in a soft-x-ray Ar(+8) laser, which is excited by a capillary Z pinch, via the combined magnetic and electric fields of the gliding surface discharge is experimentally demonstrated. Unlike soft-x-ray lasers excited by the conventional capillary Z pinches, the magnetoelectric confinement and stabilization of plasma do provide the laser operation without using any external preionization circuit.

Near-field diffraction in a two-dimensional V-groove and its role in SERS.

Optical field distribution in micro-nano geometries of miniaturized optical devices is often significantly different from that in identical but macroscopic geometries. Plasmon effects and near-field diffraction can enhance the local field intensity, leading to enhanced cross section for light absorption and scattering, which can be utilized in substrate-enhanced spectroscopies for the detection of trace amounts of adsorbed chemicals. A specific problem is an ingenious but only empirically described way to enhance signal intensity in Raman spectroscopy by the use of a substrate patterned with gold coated micron size pyramidal pits.

Diffraction of x rays in capillary optics.

Propagation of x rays generated by a small-diameter incoherent source through the capillary waveguide that satisfies the multimode condition is studied with the Fresnel-Kirchhoff diffraction theory. The strong influence of diffraction on the propagation is demonstrated. The diffraction phenomenon is manifested by the appearance of diffraction fringes in both the guide channel and the far-field zone of the capillary output.

Enhanced transmission and reflection of few-cycle pulses by a single slit.

We show that a physical mechanism responsible for the enhanced transmission and reflection of ultrashort (few-cycle) pulses by a single subwavelength slit in a thick metallic film is the Fabry-Perot-like resonant excitation of stationary, quasistationary, and nonstationary waves inside the slit, which leads to the field enhancement inside and around the slit. The mechanism is universal for any pulse-scatter system, which supports the stationary resonances. We point out that there is a pulse duration limit below which the slit does not support the intraslit resonance.

Relation between fluorescence decays and temporal evolution of excited states.

A differential equation system describing the temporal evolution of excited substates and fluorescence emission were tested using a DOPRI algorithm. The numerical solutions show that there is significant difference in the measurable parameters according to the type of connectivity among the excited substates. In the globally connected case, the fluorescence emission exhibits a double exponential behavior, and the first moment of the emitted spectrum decays with stretched exponential characterized by beta < 1.

Clinical application of laser-induced breakdown spectroscopy to the analysis of teeth and dental materials.

Objectives: The luminous plasma generated during laser ablation of dental tissue and dental materials has been analyzed to determine qualitative and quantitative elemental composition.

Background Data: The use of pulsed lasers for controlled material ablation now is frequently suggested as an alternative to mechanical drilling for the removal of caries and in tooth modification. Spectral analysis of the ablated plasma can be exploited to monitor precisely the laser drilling process in vivo and in real time.

Fields of optical waveguides as waves in free space.

It is shown by using the scalar diffraction theory and the method of images that the arbitrary field confined by the optical waveguide can be generated in free space by the appropriate light source. The correspondence between the guided and free-space waves is illustrated using several particular fields, such as the diffraction-free, self-imaging, ultra-short, solitonlike, partially coherent waves and laser fractals. In opposition to the eigenmode theory of waveguides, the field at the guide entrance can satisfy neither the guide wave-equation nor the boundary conditions.