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Recently it was conjectured that nodal domains of random wave functions are adequately described by critical percolation theory. In this paper we strengthen this conjecture in two respects. First, we show that, though wave function correlations decay slowly, a careful use of Harris' criterion confirms that these correlations are unessential and nodal domains of random wave functions belong to the same universality class as non critical percolation. Second, we argue that level domains of random wave functions are described by the non-critical percolation model., Comment: 13 pages

The BRST cohomologies of non-critical massive RNS theories are analysed in detail in the range of dimensions 1

The BRST cohomologies of non-critical massive string models are analysed in detail in the range of dimensions 1

Efficient tunable near-infrared radiation (NIR) () has been generated by temperature-tuned non-critical phase-matched (NCPM) difference-frequency mixing of Nd:YAG and tunable dye laser radiation (560 - 710 nm) in a 5 mm LBO crystal. Energy conversion efficiency of 11% at 1.54 has been achieved. A large angular and spectral bandwidth is observed. Temperature-tuned type-II non-collinear phase-matching has also been reported. Comparison with other NIR-generating crystals shows that temperature-tuned NCPM in LBO is superior to other methods.

A series of Nb doped KTP crystals are grown with seed flux method and flux pulling method. The results of our investigation on growth, morphology defects of the crystals are reported in this paper. We obtained the relationship between Nb contents and second-harmonic generation angles of the crystals. Noncritical phase matching has been realized by 4% Nb doped KTP crystal for Nd:YAG laser 1.06 μm output.

We have analysed the phase-matching features of (001)Ba2NaNb5O15/(001)KTiOPO4, (100)Ba2NaNb5O15/(100)KTiOPO4 and (100)Ba2NaNb5O15/(001)KTiOPO4 waveguides for second-harmonic generation. Theoretical results show the existence of an optimum waveguide design, which is insensitive to inhomogeneities in the waveguide thickness due to 'non-critical' phase-matching in some waveguide geometry. Using a coupled-mode theory, the overlap integral in second-harmonic generation in the film waveguide has been analysed. Some proposals are offered for increasing the overlap integral of the fundamental wave and the harmonic wave. Application of such a waveguide design can significantly ease the fabrication tolerance, leading to second-harmonic generation devices with long interaction lengths and practical conversion efficiencies.