Third-order nonlinear optical element

A third order nonlinear optical device comprising a third order nonlinear optical element formed of a single crystal having at least two optically smooth surfaces, having transparency to the input light at least one wavelength in the range from 0.65 .mu.m to 2.0 .mu.m, said single crystal comprising a charge-transfer complex consisting essentially of:

• at least one electron-accepting component selected from the group consisting of cyano compounds, quinones, nitro compounds, acid anhydride, halogens, and halogenated carbons;
• said cyano compounds being selected from the group consisting of tetracyanotheylene, tricyanoethylene, methyltricyanoethylene carboxylate, hexacyanobutadiene, tetracyanobenzene, 7,7,8,8-tetracyanoquinodimethane, 11,11,12,12-tetracyanonaphthoquinodimethane, 2,5-bis(dicyanomethylene)-2,5-dihydrothiophene, 2,5-bis(dicyanomethylene)-2,5-selenophene, hexacyanotrimethylenecyclopropane, 2,4-bis(dicyanomethylene)-1,3-dithioethane, tetracyanoquinoquinazolinoquinozoline and derivatives thereof;
• said quinones being selected from the group consisting of p-benzoquinone, naphthoquinone, 9,10-phenanthrenequinone, chloranil, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 11,11,12,12-tetracyano-1,4-naphthoquinodimethane and derivatives thereof;
• said nitro compounds being selected from the group consisting of trinitrobenzene, picric acid, 4,7-trinitrofluorenone and derivatives thereof;
• said acid anhydride being selected from the group consisting of maleic anhydride, pyromellitic acid anhydride and derivatives thereof,
• said halogens being selected from the group consisting of bromine and iodine;
• said halogenated carbons being selected from the group consisting of tetrabromemethane and bromotrichloromethane, and at least one electron-donating component selected from the group consisting of unsaturated cyclic hydrocarbon compounds, unsaturated heterocyclic compounds, chalcogen-containing compounds, quaternary unsaturated heterocyclic compounds and metals;
• said unsaturated cyclic hydrocarbon compounds being selected from the group consisting of naphthalene, anthracene, phenanthrene, pyrene, N,N,N',N'-tetramethyl-p-phenylenediamine, hydroquinone, durene, N,N-dimethyl-.alpha.-naphthylamine, diaminonaphthalene, diaminopyrene, stilbene, diaminostilbene and derivatives thereof;
• said unsaturated heterocyclic compounds being selected from the group consisting of pyridine, qunoline, phenothiazine, indole, skatole, thymine, furan, benzofuran, thiophene, selenophene and derivatives thereof;
• said chalcogen-containing compounds being selected from the group consisting of tetrathiafulvalene, tetraselenafulvalene, tetrathiatetracene, tetraselenatetracene, bithiapyrane, tetraphenylbithiapyrane and derivatives thereof;
• said quaternary unsaturated heterocyclic compounds being selected from the group consisting of N-methylphenadium, 1,2-di(N-ethyl-4-pyridinium) ethylene, quinolinium, N-methylacridinium and derivatives thereof;
• said metals being selected from the group consisting of copper, silver, lead, nickel, lithium, sodium, potassium, barium, chromium, molybdenum, tungsten, cobalt, iron, antimony, cesium and magnesium;
• said charge-transfer complex being formed of said electron-accepting component and said electron-donating component being selected so that the difference (Ip-Ea) of the electron affinity (Ea) and the ionization potential (Ip) is large enough for the formation of charge-transfer complex in the ground state;
• at least one of said components being an organic compound having a .pi.-conjugated system.