Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1992-10-28
2001-09-25
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S135000, C522S136000, C522S137000, C522S141000, C522S142000, C522S149000
Reexamination Certificate
active
06294593
ABSTRACT:
BACKGROUND OF THE INVENTION
Efficient second order nonlinear optical (NLO) processes can usually be achieved only in materials having both a large second order nonlinear hyperpolarizability tensor, &bgr;, at a molecular level, combined with a noncentrosymmetric bulk structure. Studies of NLO properties in organic crystals and powders were initiated almost simultaneously with that of inorganic crystals more than two decades ago. Certain organic crystals satisfy both of the above criteria and show bulk second order nonlinear properties considerably larger than that of traditional inorganic materials, like potassium dihydrogenphosphate (KDP) or lithium niobate (LiNbO
3
). However, they do not adequately meet the required standards for practical use in optical devices mainly owing to the great difficulty of growing crystals of sufficient size and quality. Systematic studies of organic materials and comprehensive theoretical explanations of their nonlinear behavior have been emphasized in a number of monographs, for example, in
Nonlinear Optical Properties of Organic Materials and Devices
, Williams (Ed.), American Chemical Society, Washington, D.C. (1983).
Oriented polymer systems provide an attractive alternative because of their low cost, wide variety and ease of processing. Polymer systems are conveniently prepared either by incorporating the NLO molecules into a suitable polymer matrix or by attaching the NLO molecules covalently to a polymer backbone or side chains. They will be referred hereafter as the ‘doped’ and the ‘functionalized’ polymers or systems, respectively. In both of these systems, the nonlinear optical response arises from the NLO moieties. The ‘moieties’ herein referred to are the organic NLO molecules dispersed in a polymer matrix or the NLO units that are attached to the polymer chains. Background information relating to the principals of nonlinear optical polymers, is contained in
Nonlinear Optical and Electroactive Polymers
, Prasad and Ulrich, (Eds.) Plenum Press, (1988).
Organic NLO molecules when doped in or functionalized to a polymer matrix, are in an isotropic centrosymmetric organization to begin with. It is essential to establish that the NLO moieties pack the bulk in a noncentrosymmetric fashion for the applications discussed earlier. This is effectively done by using an external electric field, e.g., corona poling, parallel plate poling or integrated electrode poling. The polymer system, after being subjected to an electric field, is referred to as a ‘poled’ polymer. A number of poled polymeric systems which show large nonlinear activity have been reported in recent literature references. Mohlmann et al.,
SPIE
, 1147:245 (1989). However, the decay in nonlinear activities with time handicaps the realization of practical NLO polymers. This is due to the deorientation of the NLO moieties when the electric field is withdrawn.
Polymer systems having inter- and intramolecular crosslinking, have been developed to overcome the relaxation problem associated with the doped and functionalized polymers. Reck et al.,
SPIE
, 1147:74 (1989); Eich et al.,
J. Appl. Phys
., 66(7):3241 (1989). In this system, polymers which exhibit second order nonlinear optical properties are disclosed which are formed by forming a network polymer from monomers during exposure to an electric field. However, network polymerization can substantially interfere with poling of nonlinear optical components, thereby significantly diminishing the optical quality of the resulting network polymer.
Co-pending U.S. Pat. No. 5,112,881, issued to B. Mandal et al. discloses an alternative approach for obtaining crosslinked, second order NLO polymers. Inter- and intramolecular photochemical reactions are used to crosslink the polymer matrix. In this system, a polymer and NLO molecules bearing similar photocrosslinkable compound are processed like a doped polymer. The system can be poled and photocrosslinked in the poled state to yield a material with stable optical nonlinearity.
SUMMARY OF THE INVENTION
This invention relates to a method and a crosslinkable polymer for forming crosslinked nonlinear optical polymers which exhibit second order nonlinear optical properties.
The method includes combining a host polymer, which can exhibit second order nonlinear optical properties, with a guest crosslinking agent. The combined host polymer and guest crosslinking agent are exposed to an electric field to pole a nonlinear optical component of the host polymer. Optionally, the guest crosslinking agent can be covalently bonded to the polymer prior to crosslinking. Also, the guest crosslinking agent can exhibit second order nonlinear optical properties. The combined host polymer and guest crosslinking agent are then exposed to sufficient electromagnetic radiation to crosslink the host polymer, thereby forming a crosslinked polymer which exhibits second order nonlinear optical properties. Examples of suitable forms of electromagnetic radiation include light and heat.
The crosslinkable polymer includes a nonlinear optical component that can be poled to cause the polymer to exhibit second order nonlinear optical properties. The polymer also includes a crosslinking agent which can crosslink the polymer while the nonlinear optical component is in the poled position, thereby forming a crosslinked polymer which exhibits second order nonlinear optical properties.
The crosslinked polymers produced by the present method have several advantages. They are easy to prepare, exhibit ultra-fast response times, show stable second order properties at elevated temperatures, perform over a broad wavelength range and have a high laser damage threshold. A unique feature of the polymers produced by this system is the high resolution obtainable in lithographic writing. The process of poling is independent of the crosslinking process in the present method, allowing them to be superimposed in a desired manner. The present crosslinked, polymeric materials are particularly suitable for second order NLO processes, such as second harmonic generation (SHG), electro-optic modulation, frequency mixing and optical parametric oscillation. They also possess excellent optical quality, stable nonlinearity and large electro-optic coefficients.
REFERENCES:
patent: 0313475 (1988-09-01), None
patent: 0313476 (1988-09-01), None
patent: 0321891 (1988-12-01), None
M. Eich et al.,J. Appl. Phys.,66(7): 3241-3247 (1989).
B. Reck et al.,SPIE,1147: 74-83 (1989).
K.D. Singer et al.,Appl. Phys. Lett.,53: 1800-1802 (1988).
M.A. Mortazavi et al.,J. Opt. Soc. Am. B..,6(4): 733-741 (1989).
Jeng Ru Jong
Kumar Jayant
Mandal Braja K.
Tripathy Sukant Kishore
Berman Susan W.
Hamilton Brook Smith & Reynolds P.C.
University of Massachusetts Lowell
LandOfFree
Method and crosslinkable polymers for forming crosslinked... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and crosslinkable polymers for forming crosslinked..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and crosslinkable polymers for forming crosslinked... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2466300