Abstract

Many types of optical intensity modulator have a transfer curve which approximates a sinusoidal function. These include Bragg modulators of both the acoustooptical and electrooptical varieties.¹ Also included are the Mach-Zehnder and directional coupler electrooptical modulators.² For most analog applications a linear transfer curve is desired. Using a Fourier analysis, it is possible to generate any given transfer curve shape with combinations of properly chosen sinusoidal components. Therefore, by combining harmonically related modulator elements, a triangular transfer curve shape can be created. Demonstrated here is use of the third harmonic to extend the linear range of a Bragg-type electrooptic modulator in the planar waveguide. It is possible to extend this technique to the other types of modulator mentioned as well. Based on a straight line curve fit, a deviation of the output intensity of less than ±1 % from the linear voltage intensity relationship has been observed over a 97% modulation range. This was accomplished while maintaining a high efficiency with 7.2 V for complete modulation.

© 1986 Optical Society of America