Volume 86, Issue 10, 15 November 1999
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
86(1999); http://dx.doi.org/10.1063/1.371528View Description Hide Description
We develop design considerations on the possibility of generating free electron laser radiation in the x-ray region of the spectrum (50–60 Å), by exploiting a frequency multiplier scheme. We propose a free electron device consisting of a relatively low energy linac (750 MeV) and three sections: an oscillator at 150 nm, an amplifier tuned at the fifth harmonic of the first and a second amplifier operating at a subharmonic of the second amplifier. The seedless amplification is ensured by the e-beam bunching, induced in the oscillator and in the second section, which plays the role of amplifier and modulator. We also explore the possibility of overcoming the problems associated with the bunching efficiency dilution, due to intracavity saturation of the first section, by discussing the regeneration of the bunching by the use of a cavity dumping, realized with a suitable e-beam energy or cavity detuning modulation.
Ultrahigh-resolution, frequency-resolved resonance fluorescence imaging with a monoisotopic mercury atom cell86(1999); http://dx.doi.org/10.1063/1.371529View Description Hide Description
A novel method of ultrahigh-resolution, frequency-resolved imaging using atomic vapor cells is proposed. The method is based on the accurate measurement of the fluorescence signal intensity distribution along the absorption path length when the signal frequency is tuned to a wing of the atomic absorption line. Two-step resonance fluorescence of vapor was used for one-dimensional imaging of the Hg resonance radiation at 253.7 nm. An imaging signal with a frequency difference of 500 MHz could be easily distinguished visually and even a frequency difference of 80 MHz could be detected after appropriate processing of the fluorescence imaging signal. Several other novel methods of one- and two-dimensional multifrequency imaging are discussed.
86(1999); http://dx.doi.org/10.1063/1.371530View Description Hide Description
We present calculations that reveal a limitation for devices that demand photonic crystals with very narrow band gaps. The opaque regions of the transmission spectra through finite length crystals may be substantially broader than the band gap of the corresponding infinite crystals. This is a consequence of the crystals’ near unit dielectric index contrast. The opaque spectral width decreases gradually with increasing thickness. Many hundreds of layers may be needed to obtain a transmission null which approaches the width of the band gap for the infinite crystal. The analysis is done for two configurations of interest for optical applications due to their relative ease of manufacturer. The first is a two-dimensional triangular array of dielectric rods for which finite difference time domain simulations are done to determine the transmission spectra. The second is a one-dimensional dielectric stack for which transmission is analytically calculated.
86(1999); http://dx.doi.org/10.1063/1.371531View Description Hide Description
A new wave-vector-space method capable of finding electromagnetic wave propagation in bounded nonlocal media without using boundary conditions is used to find the modes of an optically active planar dielectricwaveguide.Optical activity involves first-order wave-vector dispersion (nonlocality). The method finds how the altered nonlocal interaction close to the surfaces affects the waveguide modes. It is found that first-order effects of the surface layer nonlocality enter both the dispersion relation and the field profiles. The waveguide geometry is also used as an impetus to generalize several aspects of the wave-vector-space method.