David R. Haas

Phase-matched second-harmonic generation in a polymer waveguide

Quasi‐phase‐matched second‐harmonic generation has been observed in a periodically poled nonlinear optical polymer waveguide. Key elements in this demonstration include novel nonlinear optical polymers that can be spin coated, the design and fabrication of periodic electrodes for periodic poling and the optimization of waveguide parameters to obtain single‐mode waveguides with a large overlap between fundamental and harmonic modes. Phase matching of the d33 nonlinear optical coefficient occurs over a distance L=230 μm.

Development of Polymeric Nonlinear Optical Material

Abstract The molecular structural characteristics which give rise to large optical nonlinearities have been delineated. This has been accomplished by several key steps and has led to the development of a structural algorithm for the design of β molecules with high susceptibilities. High activity molecular units have been covalently attached to form polymers which can contain up to 100% of the NLO moiety, and the resulting molecular optical properties have been characterized. The second order molecular susceptibility was found to be undiminished by properly designed covalent bonding to form a polymer, and spectral characteristics were found to closely follow that of the NLO unit.

Development Of Polymeric Nonlinear Optical Materials

Commercial interest in nonlinear optical (NLO) materials is driven by the development of fiber optics, laser diodes, and high speed computing. In communications, as well as in information processing, the direction of future technology points unmistakably towards optical systems. Active materials for optical modulation, routing, and amplification are in high demand for this technology. Currently available materials for NLO applications lack many of the critical requirements for true industrial implementation. Therefore, significant programs for the development of improved NLO materials have blossomed throughout the world. Organics have been suggested as improved materials for a variety of applications ranging from conducting polymers to superconductors. For NLO applications, there is a solid foundation of basic science which clearly defines intrinsic advantages of these materials in comparison to those which are currently in use. In addition to basic material constants, organics offer the opportunity to apply molecular level science to engineer materials through application of several principles of design. In this paper, these design concepts will be highlighted in an attempt to define an industrial approach to this materials problem.

Polymeric Electro-Optic Waveguide Modulator; Materials And Fabrication

In this paper, we are reporting on organic polymeric materials designed for electro-optic waveguide device fabrication and a fabrication method for low loss integrated optical devices. These polymers are methacrylic chain polymers with non-linear optical moieties attached as side chains through variable length spacer groups. Variation of the spacer length allows the tailoring of the phase structure of the polymers as well as the glass transition temperature. For electro-optic device use, the most important material parameter is r3 3 the largest tensor element of the electro-optic tensor. We have developed polymeric materials with r3 3 values as high as 45 pm/V at 1.3 microns (98 pm/V at 632 nm) using an electrical poling process. Additionally, we have characterized optical and electrical properties of the polymer films. Further, a fabrication process for waveguide electro-optic devices from the polymers has been developed and integrated modulators have been built.

Polymeric Integrated Electro-Optic Modulators

Polymeric optical waveguides for integrated optical devices are of current interest for their potential application in very high bandwidth opto-electronic systems. We report our progress in defining and characterising channel waveguides in polymers having large electro-optic coefficients. The waveguide patterns are formed as etched channels in a polymer cladding layer. Further layers deposited onto these channels form 2-dimensional waveguides with monomode characteristics at a wavelength of 1.3 microns. The mode size is controllable and may be optimised for fibre mode coupling to minimise the coupling loss. Electro-optic phase and amplitude modulation is demonstrated for slab and channel waveguides. We report values for the off-resonance electro-optic coefficient in poled polymer films somewhat higher than the largest value in lithium niobate. The implications of such device structures for applications in high performance multi-GHz amplitude modulators are discussed. In particular, the large values of n3r and the near equality of the optical and microwave refractive indices indicates that these polymers will have significant advantage over traditional inorganic materials for wide bandwidth integrated optical modulators.

Polymeric materials for high-speed electro-optic waveguide modulators

This paper discusses some of the important material property requirements for polymeric materials in electro-optic device applications, in particular, a detailed materials characterisation of a promising polymer that is not only high in electro-optic activity after poling, but has predicted long term thermal stability of the poled structure. This material is a methacrylic chain polymer with non-linear optical moieties attached as side chains through a spacer group. Progress in fabrication and characterisation of waveguides using this polymer is also reported.

Characterization of polymeric nonlinear optical materials

The development of organic nonlinear optical materials requires the accurate measurement of its nonlinear optical and electrooptical properties. These measurements provide a guide to the synthesis and fabrication of new nonlinear organic materials with improved properties. A new technique for the electrooptical characterization of thin polymeric films is presented. This technique is used to measure the linear electrooptical Pockels effect in poled MNA/PMMA guest host glassy polymers. These results are compared to x(2) values derived from second harmonic generation studies. D. C. Kerr effect results are reported for a novel sol gel glass/PMMA composite material containing MNA. These results probe the relative mobility of MNA in PMMA at room temperature and elevated temperatures. x(3) values of several organic liquids are also measured by third harmonic generation studies in air. These values are compared with those derived from measurements in vacuum and good agreement is found between the two techniques.

Polymer-based electro-optic modulators: fabrication and performance

A wide bandwidth Mach-Zehnder modulator with on/off switching powers of 20 dBm, a bandwidth of up to 20 GHz, and insertion losses around 5 dB is presented which is based on HCC-1232 polymer. Attention is given to material properties of HCC-1232, the modulator design, and preliminary test results.

Electro-optic and nonlinear optical polymers and devices

Early work at Hoechst Celanese1 demonstrated that methacrylate polymers with mesogenic side chains could be made with reasonably large electro-optic activity. The mesogenic side chains are polar so that a non-centrosymmetric structure can be obtained by heating a film near its Tg in a strong d.c. electric field and thus orienting the side chains. In Figure 1, the general structure of methacrylate based electro-optic polymers using polar nitro-stilbene chromophores is shown.