Design and Analysis of Electro-Optic Effect-Driven Directional Coupler for Realization of Optical BCD to Excess-3 Code Converter Circuit

This research investigates the application of an electro-optic effect-driven directional coupler in the design of an optical binary-coded decimal (BCD) to excess-3 code converter circuit. The work explores electro-optic modulation in GaAlAs 3µm×3µm modulators with directional couplers. A theoretical study and practical validation demonstrate that achieving 100% modulation requires minimal changes in the refractive index difference (Δ n g ). For a 1 cm length GaAlAs modulator with a directional coupler configuration, a fluctuation of approximately Δ n g ≈1×10 −4 can entirely switch light of a 900 nm vacuum wavelength from one waveguide to another. The required electric field is expected to be roughly 3×10 4 V/cm equivalent to a voltage of 10 V across the 3 µm thick channel, as derived from the coupled wave theory. This study presents a comprehensive analysis of the extinction ratio, contrast ratio, and amplitude modulation characteristics of the proposed optical code converter circuit. These findings illustrate that electro-optic effect-driven directional couplers can efficiently process signals, paving the way for advances in optical computing and digital electronics.