The new nonlinear optical (NLO) crystal BaGa4S7 for the mid-infrared (IR) has been grown by a Bridgman-Stockbarger technique. Polycrystalline materials with stoichiometric composition were synthesized from BaS, Ga, and S as the initial materials by solid-state reactions. The ultraviolet (UV) and IR transmittance of the crystal was determined with polished crystal pieces. The UV and IR optical absorption edges were found to be at 350 nm and 13.7 μm, respectively. From optical measurements of second harmonic generation on powders, the NLO coefficient d 33 was determined to be 12.6 pm/V. The laser damage threshold of a single crystal reached about 1.2 J/cm2 at 1.064 μm. The Vickers-hardness value of the crystal is 327.5 HV5, which is equivalent to Mohs’ hardness of about 5.

In this article, a new technique is proposed which can handle the singularity problem arising in the MoM solution of the electric field integral equation. The method involves MCI technique in evaluation of the moment matrix elements. One major advantage of the MCI technique is that it removes the singularity problem arising in integration of singular integrand without any analytical modification or approximation to the integrand by only employing the "local correction technique," where the uniformly distributed random points are avoided from falling in the vicinity of the observation points. The technique is applied to the problem of scattering from metallic structures for three different test cases showing the local correction for the singular points in each case. It is evident that this new technique is capable of handling the singularity problem very efficiently and easily. ACKNOWLEDGMENT

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