Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfonate esters
Reexamination Certificate
1996-10-10
2003-01-07
Gerstl, Robert (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfonate esters
C385S122000, C385S143000
Reexamination Certificate
active
06504042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the use of soluble, amorphous, conjugated spiro-linked oligomers and polymers as materials for nonlinear optics. It furthermore relates to optical beam guides (waveguides) which are made from these compounds or comprise them and exhibit non-linear optical effects, and to non-linear optical structural elements (components) which are based on such beam guides.
2. Description of the Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
The term “non-linear optics” describes phenomena, and application thereof, which chiefly occur during interaction between high light intensities or high electric field strengths and specific materials. These effects are based on the polarization of matter by an electric field. This can be represented in a power series:
P=&khgr;
(1)
E+&khgr;
(2)
E
2
+&khgr;
(3)
E
3
+ . . .
The &khgr;
(n)
are the so-called electric susceptibility functions. E is the electric field and can comprise several frequency components and may therefore be made up of light or a voltage or a combination thereof. The susceptibility is linked to the so-called molecular hyperpolarizability:
&khgr;
(2)
~N&bgr;; &khgr;
(3)
~N&ggr;,
in which N is the density of the active molecules and &bgr; and &ggr; represent the hyperpolarizabilities of the 2nd and 3rd order. The susceptibilities usually decrease with increasing potency, and non-linear optical (NLO) effects therefore become visible only at high field strengths. Furthermore, all susceptibilities of an even order are zero if the individual molecules are arranged centrosymmetrically in the material or the molecules themselves show inversion symmetry.
Effects of the 3rd order, which also occur in systems with inversion symmetry, are, for example, the 4-wave mixture in which light rays having three different frequencies form one light ray having a fourth frequency. The degenerate 4-wave mixture in which all 4 rays have the same frequency is of particular interest for applications. This leads to the so-called optical Kerr effect, in which the refractive index of the material depends not only on the wavelength but also on the intensity of the light ray. On the basis of the Kerr effect, real-time holograms can be established, or purely optical circuit elements which could be suitable for use in optical computers can be developed.
For optical circuit elements in particular, it is advantageous and often necessary for the NLO-active materials to be employed as beam guides either in a light-conducting fiber or as a planar waveguide on a substrate. On the one hand, a waveguide arrangement allows the construction of integrated optical structural elements, and on the other hand the waveguide has the effect that the light intensity and therefore the field strength remain high over a longer path and the NLO effects are greater. However, this can only be achieved if the optical losses in the waveguide which occur due to absorption and light scattering are as small as possible. Examples of structural elements based on NLO-active beam guides are opto-optical couplers, Mach-Zehnder interferometers, mode-selective couplers and prism couplers, which can be employed in communications technology or for optical computers. The invention relates to these and other structural elements and applications, which are described, for example, by G. Stegeman et al. in
Nonlinear Optical Effects in Organic Polymers
, pages 257-276 (Dordrecht: Kluwer, 1989), using conjugated spiro compounds, but is not limited to these structural elements and applications mentioned.
Beam guides can be employed appropriately for applications in non-linear optics only if the optical losses which occur due to absorption and light scattering are as low as possible. An ideal material for use in NLO of the 3rd order should absorb as little as possible at the desired use wavelength, and should also have a homogeneous, preferably an amorphous, structure, in order to prevent light scattering. Furthermore, the material should be readily processible and optically, chemically and thermally stable.
For effects of the 3rd order, conjugated polymers and oligomers, for example poly(phenylenevinylene), poly(diacetylene) or sexi(thiophene), have proven to be interesting materials having relatively high susceptibilities of the 3rd order. Examples of conjugated organic materials for non-linear optics of the 3rd order are described by G. H. Cross in
Nonlinear Optical Materials
, pages 189-225 (London: Blackie Academic and Professional, 1993) and by D. Neher in
Advan. Mater.
, 7, 8, pages 691-702 (1995). The substances available to date cannot fulfill all the above-mentioned conditions at the same time. Many of the compounds, for example poly(thiophenes), poly(anilines) or poly(phenylenevinylenes), are intensely colored and are therefore unsuitable for waveguides in the visible range. Poly(arylenevinylenes) furthermore are often sensitive to oxygen and light. Conjugated polymers and oligomers moreover are usually insoluble or poorly soluble, and are therefore difficult to process from solution using typical coating processes, and often form polycrystalline, light-scattering layers. This applies in particular to colorless compounds such as, for example, poly(phenylenes). However, the method frequently used of increasing the solubility and suppressing crystallization with long-chain substituents is accompanied by a dilution of the active units and a reduction in NLO susceptibility. Furthermore, the mechanical stability of the films is impaired as a result.
OBJECTS OF THE INVENTION
It is an object of the present invention to develop a method of using a spiro compound as materials for non-linear optics which improves the solubility, stability, achives good non-linearly optical activity, low optical losses and avoids the disadvantages of problems mentioned.
It is also an object of the present invention to provide a non-linearly optical structural element, which comprises or consists of a monomeric or polymeric spiro compound as described above. Preferably, non-linearly optical effects of the third order are exploited in this structural element.
It is yet an object of the present invention to provide a non-linearly optical structural element, which comprises an optical waveguide comprising or consisting of a monomeric or polymeric spiro compound as described above. Preferably this non-linearly optical structural element is an opto-optical coupler, a Mach-Zehnder interferometer, a mode selective coupler or a prism coupler.
SUMMARY OF THE INVENTION
It has been found, surprisingly, that the monomeric and polymeric spiro and heterospiro compounds described below are particularly suitable as materials for non-linear optics, since they do not have the above-mentioned disadvantages because they are soluble, stable and amorphous substances and at the same time have a good non-linearly optical activity and low optical losses. In the context of this application the term “spiro compound” includes monomeric and polymeric carbo spiro and hetero spiro compounds.
Accordingly, an aspect of the invention relates to the use of spiro compounds of the formula (I),
in which &psgr; is C, Si, Ge or Sn, preferably C, Si or Ge, more preferably C or Si, and in particular C, and K
1
and K
2
independently of one another are conjugated systems, as materials in non-linear optics.
DETAILED DESCRIPTION OF THE INVENTION
Spirocompounds are compounds in which two ring systems are linked by a single tetravalent atom. This atom is referred to as a spiro atom, as explained in
Handbook of Chemistry and Physics,
62nd edition (1981-2), CRC Press, pages C-23 to C-25.
Preferred compounds of the formula (I) are 9,9′-spirobifluorene derivatives of the formula (II),
in which &psgr; has the above-mentioned meanings, and in which the benzo groups can be substituted and/or fused independently of one another.
Pa
Lupo Donald
Salbeck Josef
Frommer Lawrence & Haug
Hoechst Aktiengesellschaft
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