Phases and Third-Order Optical Nonlinearities in Tetravalent Metallophthalocyanine Thin Films

The third-order optical susceptibilities χ1111(3)(-3ω; ω, ω, ω)sfortwodifferentphasesinvanadylandtitanylphthalocyanine (VOPcandTiOPc) vacuum-depositedthinfilmsaredeterminedbyopticalthird-harmonicgeneration (THG) measurementsatwavelengths 1543 nmand 1907 nm. Thermalannealingcausesaphasetransitionwhichaccompaniesaredshiftintheirabsorptionspectraandanincreaseinthe χ^(3) valueof 2-5 timesinVOPcandTiOPcfilms. Theenhancementofthethird-orderopticalnonlinearitiesintetravalentphthalocyaninefilmsisdiscussedintermsofmolecularpacking.