Means for assessing the nonlinear optical properties of nanoscale materials are of key importance for the advancement of active nanophotonics. By correlating second-harmonic generation (SHG) with electron backscattered diffraction from single GaN nanowires (NWs), we demonstrate that far-field microscopic imaging of SHG offers an approach for distinguishing crystallographic orientations of NWs lying on a substrate. The quasi-static approximation, which should prove useful in describing many nanophotonic behaviors, is shown to satisfactorily account for the SHG data.

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Experimental Sectiong 2-(4-Pyridyl)-5-n-propylaminothiadiazole.---N~-Iso~~icoti11oylh:4-n-pl.opyltliiosemicarba~ide (2.38 g, 0.01 mole) was added to concd H2S:04 (5 ml) ill small portions. The mixt was shaken vigorously to form an homogeneous soln and set aside (30 min). I t was then poured in ice water and neutralized (NatCOS). The product was collected and crystd (EtOH), to form yellow shining Iieedles. 5-p-(1 -Cyelohexylureidosulfonyl)phenyl-4-ethyl-4H-l,2,4triazole-3-thiol.-4-Eth~l-5-p-sulfamoyl-phe11y1-4H-l,2,4-t riazole-&thiol (2.15 g, 0.01 mole) was dissolved in dry AIe2CO (50 nil). T o this soln were added anhyd K2CO3 (4.0 g) and cyclohesyl isocyanate (1.5 ml), and the mixt was refluxed on steam bath for 8 hr. Acetone was distd off, and the residue was dissolved in 1120, filtd, rooled, and acidified (IICl), when n sticky material iepd which solidified after long standing. It was filtd, washed (Ilk)), and crynld (EtOH). Other sulfonylureas were prepd by following the above procedure.Other compds (Table I ) were prepd similarly.(9) The melting poinfs are rapillary melting points and are uncor. Analyses indicated 113. syml,olr of the elements \yere within 2~0 . 4~ of the tlieor values.

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