Abstract: A pit-forming optical recording medium comprises a substrate supporting a film of optically deformable recording material comprising an organic dye for absorbing optical signals of modulated electromagnetic radiation applied to the film and thereby causing corresponding deformations of the film when the signal intensities exceed predetermined threshold levels. The dye is a phthalocyanine compound or mixture of phtalocyanine compounds in which each of at least five of the peripheral carbon atoms in the 1, 4, 5, 8,9, 12, 13 or 16 positions (the "3,6-positions") of the phthalocyanine nucleus, as shown in Formula I, is linked by an atom from Group VB or Group VIB of the Periodic Table to a carbon atom of an organic radical. In preferred compounds each of the eight 3,6-positions is linked by an atom from Group VB or Group VIB, especially sulphur, selenium or nitrogen, to an organic radical.

Abstract: An azo compound of the formula: ##STR1## wherein R is an non-hydrophilic aliphatic or cycloaliphatic group containing from 8 to 40 carbon atoms;m is 0 or 1;R.sup.1 is NO.sub.2, CN or COOR.sup.2 ;R.sup.2 is H or C.sub.1-4 -alkyl;n is from 1 to 4 andR.sup.3 is H, a metal or a group containing a tetravalent N atom.The compound has non-linear optical properties which make it suitable for use in an optical element such as a waveguide, for altering the characteristics of light passing through the element.

Abstract: Optical elements having non-linear optical properties comprising a compound of the formula: ##STR1## wherein E is an electron donorA is an electron acceptor;and W, X, Y & Z are each independently H or any group capable of attachment to the pyrazolyl ring; in which the molecules of the compound are aligned so that the element has a net non-centrosymmetry, a method for their preparation, optical devices comprising such elements, and compounds of formula I.

Abstract: Optical elements having non-linear optical properties comprising a compound of the formula: ##STR1## wherein D is an electron donorA is an electron acceptor;and W, X, Y and Z are each independently H or any group capable of attachment to the pyrazolyl ring; in which the molecules of the compound are aligned so that the element has a net non-centrosymmetry, a method for their preparation, optical devices comprising such elements, and compounds of formula I.

Abstract: An optical element, such as a wave guide, having non-linear optical properties, suitable for use in optical devices in which it is desirable to alter the characteristics of the light, comprising a transparent or reflecting substrate having at least a partial superficial coating comprising alternating monolayers of a first non-linear optical (NLO) compound of the formula: ##STR1## wherein R is an non-hydrophilic aliphatic or cycloaliphatic group containing from 8 to 40 carbon atoms;m is 1 or 2;R.sup.1 is NO.sub.2, CN or COOR.sup.2 ;R.sup.2 is H or C.sub.1-4 -alkyl;n is from 1 to 4; andR.sup.3 is H, a metal or a group containing a tetravalent N atom anda second NLO compound of the formula: ##STR2## wherein T is H, a metal or a group containing a tetravalent N atom;X is S, O, ##STR3## T.sup.1 is NO.sub.2, CN or COOY; Y is selected from H, C.sub.1-4 -alkyl, a metal or a group containing a tetravalent N atom;T.sup.2 and T.sup.

Abstract: Optical elements comprising a non-centrosymmetric compound comprising an electron donor and an electron acceptor linked by a conjugated bridging group, in which the electron acceptor is a nitroso group, in which element the molecules of the compound are aligned so that the element has a net non-centrosymmetry, a method for their preparation, optical devices comprising such elements, and some of the compounds.

Abstract: (i) A compound of the formula: ##STR1## wherein R is H, a metal or a group containing a tetravalent N atom;X is ##STR2## R.sup.1 is NO.sub.2, CN or COOY; Y is H, C.sub.1-4 -alkyl, a metal or a group containing a tetravalent N atom;R.sup.2 & R.sup.3 are each independently H or a non-hydrophilic aliphatic or cycloaliphatic group containing up to 30 carbon atoms;R.sup.4 & R.sup.5 are each independently H or a non-hydrophilic aliphatic or cycloaliphatic group containing up to 30 carbon atoms;and R.sup.6 & R.sup.7 are each independently H or a non-hydrophilic group containing up to 4 carbon atoms;or R.sup.4 & R.sup.6 together comprise ring fused to Ring A and R.sup.5 & R.sup.7 are as hereinbefore defined;or R.sup.5 & R.sup.7 together comprise ring fused to Ring A and R.sup.4 & R.sup.6 are as hereinbefore defined;or R.sup.2 & R.sup.4 together with the N atom to which R.sup.2 is attached from a ring fused to Ring A and R.sup.3 & R.sup.5 are as hereinbefore defined;or R.sup.3 & R.sup.

Abstract: A compound of the formula: ##STR1## wherein E is an ethenyl group of the formula: ##STR2## in which X is H when Y is NO.sub.2 ;Y is H when X is NO.sub.2 ; orX is CN when Y is CNwhich has the capacity to form a crystal in which the molecules are aligned substantially in the same manner giving it non-linear optical properties. The crystalline product is thus adapted for use in devices exhibiting non-linear optical effects.

Abstract: (i) A compound of the formula: ##STR1## wherein R is H, a metal or a group containing a tetravalent N atom;X is S, O, ##STR2## R.sup.1 is NO.sub.2, CN or COOY; Y is H, C.sub.1-4 -alkyl, a metal or a group containing a tetravalent N atom;R.sup.2 and R.sup.3 are each independently H or a non-hydrophilic aliphatic or cycloaliphatic group containing up to 30 carbon atoms;R.sup.4 and R.sup.5 are each independently H or a non-hydrophilic aliphatic or cycloaliphatic group containing up to 30 carbon atoms; andR.sup.6 and R.sup.7 are each independently H or a non-hydrophilic group containing up to 4 carbon atoms; orR.sup.4 and R.sup.6 together comprise ring fused to Ring A and R.sup.5 and R.sup.7 are as hereinbefore defined; orR.sup.5 and R.sup.7 together comprise ring fused to Ring A and R.sup.4 and R.sup.6 are as hereinbefore defined; orR.sup.2 and R.sup.4 together with the N atom to which R.sup.2 is attached form a ring fused to Ring A and R.sup.3 and R.sup.5 are as hereinbefore defined; orR.sup.3 and R.sup.

Abstract: A metal dithiene of the formula: ##STR1## wherein R.sup.1 is C.sub.3 to C.sub.20 alkyl;R.sup.2 is selected from alkyl, alkylamino, dialkylamino, alkylthio and alkoxy in which each alkyl contains up to 20 carbon atoms;R.sup.3 is H, halogen or a group represented by R.sup.2 ; andM is a metal selected from Groups Ib, IIb, VIIb, and VIIIb of the Periodic Table,and a composition of the metal dithiene in a liquid crystal medium. The composition is suitable for use in a light valve for a laser-addressed liquid crystal display.

Abstract: A metal dithiene of the formula: ##STR1## wherein R.sup.1 is C.sub.3 to C.sub.20 alkyl;R.sup.2 is selected from alkyl, alkylamino, dialkylamino, alkylthio and alkoxy in which each alkyl contains up to 20 carbon atoms;R.sup.3 is H, halogen or a group represented by R.sup.2 ;and M is a metal selected from Groups Ib, IIb, VIIb, and VIIIb of the Periodic Table,and a composition of the metal dithiene in a liquid crystal medium. The composition is suitable for use in a light valve for a laser-addressed liquid crystal display.

Abstract: An infra-red absorbing phthalocyanine compound in which each of at least five of the peripheral carbon atoms in the 1, 4, 5, 8, 9, 12, 13 or 16 positions (the "3,6-positions") of the phthalocyanine nucleus, as shown in Formula I, is linked by an atom from Group VB or Group VIB of the Periodic Table, other than oxygen, to a carbon atom of an organic radical. In preferred compounds each of the eight 3,6-positions is linked by an atoms from Group VB or Group VIB, especially sulphur, selenium or nitrogen, to an organic radical.