Compositions – Light transmission modifying compositions – Infrared
Patent
1988-10-17
1991-07-30
Maples, John S.
Compositions
Light transmission modifying compositions
Infrared
252589, 252582, 25229901, 350350R, 350355, 350 963, F21V 904, C09K 1952, G02F 113
Patent
active
050358391
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to materials of non-linear optical properties in which one layer containing components having a hyperpolarizability of the second order differing from zero is attached to a substrate via hydrogen bridges.
Non-linear optics are concerned with the interaction of electromagnetic fields in various media and with the formation, associated therewith, of new fields having different properties. Materials with non-linear optical properties possess a dielectric susceptibility of the second order which is dependent on the field strength and which is the cause of a number of dispersive processes: frequency doubling (second harmonic generation=SHG) makes it possible to produce light of half the wavelength in comparison with the incident light; the electro-optical effect (Pockels effect) makes it possible to alter the refractive index when an electric field is applied; and methods of sum and difference frequency mixing and also frequency division permit the continuous tuning of laser light.
A large number of technical applications results from the effects listed above. Electro-optical switch gear, the control of frequency and intensity in laser technology, holography and the realms of information processing and integrated optics constitute fields of use for materials having non-linear optical properties of the second order.
Materials having electrical susceptibility functions of the third order are suitable for the production of purely optical switch gear and hence as waveguides for the construction of purely optical computers.
In order to be suitable for use in the field of non-linear optics of the second order, materials of this type must meet a number of requirements.
In addition to a non-centrosymmetrical molecular arrangement within the crystal, suitability for technical use requires the highest possible values of dielectric susceptibility X.sup.(2).
A number of inorganic substances, such as, for example, potassium dihydrogenphosphate or lithium niobate, exhibit non-linear optical properties. However, all these compounds suffer from a very wide variety of disadvantages. In addition to insufficient values of dielectric susceptibility of the second order, inorganic compounds are frequently deficient in adequate photostability when subjected to treatment at high intensities of light, or they can only be prepared and processed with difficulty.
Organic compounds of the nitroaniline type are known from Garito et al., Laser Focus 18 (1982) and from EP 0,091,838. However, their relatively good values of photochemical stability and dielectric susceptibility of the second order are accompanied by poor crystallizability and inadequate mechanical stability. In particular, it is not possible to use these materials to prepare thin layers such as are required by integrated optics.
Polymers are distinguished by high resistance to mechanical stress and good stability towards chemicals. Molecules which have non-linear optical properties and are fastened to the polymer skeleton or dissolved in polymers should, therefore, display advantageous values of dielectric susceptibility in the non-centrosymmetrical environment.
Polymers having non-linear properties of the second order can be prepared by applying an external field to films which are doped with statistically oriented molecules and have been heated above the glass transition temperature. This results in a polarity in the intercalated molecules, which imparts anisotropy to the polymer medium when the latter has solidified. Polymers prepared in this manner which have non-linear optical properties and in which p,p'-dimethylaminonitrostilbene is used as the host molecule, have been described by Meredith et al., Macromolecules 15 (1982) 1385.
Shibaev et al., Polymer Communications 24 (1983) 364, report the field-induced orientation of liquidcrystal polymers having mesogenic side groups.
U.S. Pat. No. 4,412,059 discloses a polymer material having cholesteric mesophases which are accessible to controlled orientation by means of electric or
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Dorsch Dieter
Eidenschink Rudolf
Marowsky Gerd
Rieger Bernhard
Maples John S.
Merck Patent Gesellschaft mit beschrankter Haftung
Treanor Richard
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