Hong-Tai Man

Simple reflection technique for measuring the electro‐optic coefficient of poled polymers

A simple reflection technique for measuring the electro‐optic coefficient of nonlinear optical polymeric films is described. The technique is based on the polarization rotation of a laser beam due to the electro‐optic effect. It requires no waveguiding and can be used to measure polymeric films during, as well as after, the electrical poling process. The results are in excellent agreement with those obtained from the more conventional but much more time consuming waveguiding method.

Long term stability of a poled side-chain nonlinear optical polymer

A side-chain nonlinear optical polymer consisting of copolymers of 4-methylamino-4′-nitrostilbene and methacrylate was poled and shown to be orientationally stable for almost 8 yrs. At approximately 110 °C below its glass transition, its electrooptic coefficient was reduced by less than 25% of its initial value. In addition, adding an annealing step during the poling process further improved its orientational stability. These behaviors are consistent with existing empirical models describing poling relaxation of nonlinear optical polymers, and demonstrate that with appropriate molecular design, they can become viable nonlinear optical materials for commercial devices.

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.