Masaaki Okunaka

New method of measuring second harmonic generation efficiency using powder crystals

A new method of measuring second‐harmonic generation (SHG) efficiency using powder crystals is proposed. The second harmonic, which is generated by the evanescent wave under total reflection conditions, is phase matched for every element of the second‐order optical nonlinear coefficient, whether each element is phase matchable in a bulk crystal or not. Observing this phase‐matched second‐harmonic power gives the SHG efficiency, regardless of the phase matchability in a bulk crystal, even if powder crystals are used as a sample.

THE STRUCTURE AND NONLINEAR OPTICAL PROPERTIES OF 3-N-PROPYLAMIDE-4-(4-HEXYLOXYPHENYLETHYNYL)-NITROBENZENE

Abstract We have synthesized the tolane derivative 3- n -propylamide-4-(4-hexyloxyphenylethynyl)-nitrobenzene 1 and examined its second-order nonlinear properties and crystal structure. Compound 1 crystallizes in the space group C1c1 with a =27.667(6), b =4.910(2), c =20.856(3) A, β =128.36(3)° and Z =4, and shows a high second-order nonlinear optical efficiency. It has an intermolecular hydrogen bond between CO and N–H in the amide group. This hydrogen bond plays an important role in forming a non-centrosymmetric structure appropriate for nonlinear optical materials.

Laser microformation of thin film on glass substrate for repair of transparent defects on high-density masks

Summary A new technique is developed for repairing transparent defects on high density masks for VLSI. A thin Ag-Ta organometallic film is first spin-coated onto a photomask and baked. Then an Ar laser microspot is applied to a small area on this film. After rinsing the mask with a solvent, an opaque layer remains at the laser-irradiated spot and the rest of the organometallic material is washed away. The opaque film formed locally by laser irradiation is dense enough to prevent light transmission and durable enough to withstand repeated washing with strong alkali and acid solutions.