The backward scattering of TM-polarized light by a two-side-open subwavelength slit in a metal film is analyzed. We show that the reflection coefficient versus wavelength possesses a Fabry-Perot-like dependence that is similar to the anomalous behavior of transmission reported in the study [Y. Takakura, Phys. Rev. Lett. 86, 5601 (2001)]. The open slit totally reflects the light at the near-to-resonance wavelengths. In addition, we show that the interference of incident and resonantly backward-scattered light produces in the near-field diffraction zone a spatially localized wave whose intensity is 10-103 times greater than the incident wave, but one order of magnitude smaller than the intra-cavity intensity. The amplitude and phase of the resonant wave at the slit entrance and exit are different from that of a Fabry-Perot cavity.
The intensity distributions of the coherent and partially coherent x-rays passed through a poly-capillary lens have been computed at the focal plane. The computations showed that at the appropriate experimental conditions the interference phenomenon does affect the intensity distribution. In the case of the coherent input radiation with the photon energy of 0.1 keV, the interference fringes were observed, while the non-coherent x-ray radiation produced no interference-like intensity distributions.
The recent progress in the development of the tabletop soft x-ray lasers pumped by capillary discharges has opened the possibility of the widespread use of these coherent sources for applications. In this paper, we present the latest results achieved in our laboratory concerning the optimization of a 46.9nm capillary discharge pumped soft x-ray laser and the imaging of the laser beam on Lithium Fluoride (LiF, films), which appears to be a new promising x-ray detector. The use of LiF allows a high spatial resolution (smaller than 1μm) on large areas, high-contrast imaging and simple manipulation. The laser, which is pumped by 18-20kA, 150-180ns long current pulses at a repetition rate of 0.1Hz, is produced in 3.2mm diameter up to 45cm length alumina capillary tubes filled with Ar at the initial gas pressure of 300-600mTorr. At the capillary lengths examined, the laser is operating in the saturation regime giving an output energy of about 300μJ per pulse and high coherence degree.
The effect of the transverse-direction electrical fields on the stability and dynamics of a capillary discharge Z-pinch, at conditions for which soft x-ray lasing in Ne-like Ar has been demonstrated, is studied. It is shown that the transverse electrical fields of the sliding surface discharge provide the instability-free compression and heating of the plasma. The stable and homogeneous heating and compression allows achievement of the appropriate conditions for the soft x-ray lasing in Ne-like Ar. Numerical calculations using the MHD model of the discharge yield new predictions for dynamics and stability of the plasma collapse in the presence of the transverse electrical fields and explain details of experimental observations without artificial adjustments.
In the study (SPIE 4144, 128 (2000)) we have presented results of the experimental study of a strongly nonuniform spatial distribution of output keV and sub-keV radiation, that transported by different types of glass mono- and policapillary converters from the point x-ray laser plasma and z-pinch plasma sources. In this paper the features of x-ray radiation are analyzed theoretically using the Fresnel-Kirchhoff diffraction theory and the method of images. We show that the wave effects can strongly affect properties of the x-ray capillary optics.
Wave effects in mono- and poly-capillary x-ray optics are studied theoretically. We consider the guided propagation of continuous-wave x-ray radiation in the spectral region of 0.01-1 nm. Optical guiding of x-ray ultra-short pulses is also studied. We show that the wave effects can strongly affect properties of x-ray capillary optics. The necessary conditions for the strong influence of the diffraction and interference on the guided propagation of x-rays are presented.
We report on a fast soft x-ray source consisting in a high temperature small diameter plasma column produced by electric discharge in a ceramic capillary. This source was developed to produce pulses of few hundred nanosecond duration for EUV lithography, x-ray microscopy applications and also with the aim of developing a soft x-ray amplifier. We obtained experimental results concerning the intensity and spectral analysis of the emitted x radiation pumped by a 30-40 kA, 100-200 ns, electric discharge at 1 Torr pressure in Ar gas. We refer also on the spectra obtained using CO2, as plasma medium, after the optimization of the discharge setup and electrical parameters.
This research is a continuation of our activity on the development and study of glass-capillary optics devices that started in 1974. We presented new results of the experimental study of a strongly nonuniform spatial distribution of output keV and sub-keV radiation, that transported by different types of glass mono- and polycapillary converters from point x-ray laser plasma and z-pinch plasma sources.
Propagation of the soft x-rays, which have been generated by a small-diameter incoherent source, through the straight and tapered plane capillaries is studied using the Fresnel- Kirchhoff diffraction theory. The diffraction and interference are manifested by appearance of the diffraction fringes in the far-field zone of the capillary output. The experimental data presented in the paper confirms such behavior of the x-ray radiation.
Propagation of the x-rays generated by a small incoherent source through the capillary, is studied using the Fresnel- Kirchhoff diffraction theory. The influence of the diffraction on the propagation is demonstrated. The diffraction is manifested by the appearance of the diffraction fringes in both the guide channel and the far- field zone of the capillary output. The experimental data which confirms such a behavior of the x-rays is also presented. The result give a confirmation for the interference effects recently observed in capillary optics.
Patrizia Albertano, Mauro Belli, Sarah Bollanti, Paolo Di Lazzaro, Anatoly Faenov, Francesco Flora, Gualtiero Giordano, Antonio Grilli, Fiorenza Ianzini, Sergei Kukhlevsky, Tommaso Letardi, Alessandro Marinai, Alessandro Nottola, Libero Palladino, Tatiana Pikuz, Armando Reale, Lucia Reale, Anna Scafati, Giovanni Schina, Maria Tabocchini, I. C. Edmond Turcu, Kostandia Vigli-Papadaki
A large volume excimer laser, HERCULES, has been successfully applied as pump for a soft x-ray plasma source. The laser pulse duration has been varied from the natural value of 120 ns down to 10 ns, reaching different emission spectra from the plasma which have resulted to be optimum for different applications of the plasm source itself. Some experimental results on the applications of the source to different fields are presented; the choice of the best laser parameters in relation to the applications of the plasma source are also discussed.
We propose to enhance the gain of Ne-like ion capillary lasers by the utilization of two discharge pulses. A first pulse working in the pinch regime mode is designed to create the cold-plasma column with the required ionization degree, followed by a second fast high-voltage pulse to do the effective collision excitation. The second pulse, which heats the electrons to a kinetic temperature Te greater than Tecold in times shorter than the ionization time, increases the laser gain. In the two stage pumping scheme, both the amplitude of each of the pulses and the delay between them can be adjusted for independent control of the ionization degree and excitation rate. Numerical estimations performed for the low-Z-ion (Na+1, . . ., Ar+8) lasers with the double pulse pumping predict enhancement in gain by a factor of approximately 10. In addition, the extension of two-stage electrical pumping to the high-Z-ion collision and recombination laser schemes is discussed. Description of the experimental set-up constructed for such experiments and some related measurement data are also presented.
A simple technique of the generation of high-density metal- vapor columns for x-ray capillary lasers is demonstrated. The method is based on vaporization of the electrode material in the low-pressure (P less than 1 torr) capillary microsecond- discharge. High-density (NAl greater than 1017 cm-3), small-diameter (1 divided by 6 mm), long (5 divided by 20 cm) Al-vapor columns have been produced. The Al- vapor density along the capillary and the time-resolved spectra from Al-vapor plasmas are presented. The Al-vapor density and profile were controlled by varying the discharge parameters.
We present an analysis of the pulsed waveguide modes (recently introduced in [1, 2]) and their propagation constants for an X-ray capillary laser. The optical losses of the pulse-waveguide modes are calculated for the SiO2 - capillary laser operating in the spectral region λ = 0.62 - 12.4 nm. We shows that the guiding effect plays the important role in. the laser-beam formation. By employing the pulsed-mode approach, we calculate the angle intensity-distribution of the output radiation.
A small-bore diffusion relaxed N2-laser (P<200 Torr) with longitudinal and transverse excitation in single- and multichannel discharge configurations is developed. We show that the maximum repetition rate and specific average power of the laser are increased with the decrease of the characteristic transverse dimension of the discharge channel. An 8-kHz repetition rate and average power of 6.4 mW are obtained in very compact laser structures. A specific average power of about 160 mW/cm3 is achieved, that is a few times higher than that extracted from largebore plasma tubes. The laser with transverse excitation produces 30-kW pulses at 500 Hz. The waveguide effect in the laser channel and its influence on the spatial distribution and coherence of the laser radiation are also studied.
In this work we present the results of the experimental and theoretical investigation of the optical characteristics waveguide N2 lasers. We have shown that the theory of stationary modes of the waveguide resonators does not describe the peculiarities of pulsed generation. We have developed a model of the pulsed nodes of the waveguide resonators. The results of the model are in agreement with the experimental data.
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