Research On Y-fed Directional Coupler Electro-optic Modulator Based On Organic Polymer

External modulators with high linearity are required in high-performance analogoptical communication systems such as optical phased array radars and CATVs. Thedynamic range of these systems will be degraded by the nonlinear distortions from thesinusoidal modulation curve of the conventional M-Z modulators. A number of linearitytechniques have been proposed over the past years, which involve either electroniccompensation with strict bias control or multiple modulator series schemes. Thesetechniques are based on M-Z modulators and a common shortcoming is the complexstructures. The Y-fed directional coupler electro-optic(EO) modulator which has atradeoff between device complexity, stability and the linearity of performance is widelyconcerned recently.In this thesis, a two-section Y-fed directional coupler modulator based on organicEO polymer is presented. The linearity of this modulator can be enhanced significantlyby the appropriate choice of the normalized coupling length of each section. Anoptimized combination of the normalized coupling lengths of the two sections (s1, s2) isset to (2.86,2.86) by the theoretical analysis of SFDR, maximum modulation depth,normalized driving voltage and manufacturing tolerance.A Y-fed directional coupler modulator is designed to investigate the referredscheme at low-speed operation. The simulation of the UV15:IPC-E/PSU:NOA61opticalwaveguides is carried out by integrated optical theory and design software OptiBPM9.0.The whole length of the waveguide structure is4cm and the insertion loss exhibits7.9dB. And a pseudo domain-inverted electrode(zigzags electrode) is acted as thedriving electrode of the mentioned modulator and determined as3μm-thickness and20μm-wideness. And the characteristic impedance is concerned at50.0649on theSmith chart.The modulators are fabricated in labs by the micro-fabrication techniques finally.The existing difficulties and problems in the processing are analyzed and solved.It is believed that the practical implementation of the Y-fed directional couplermodulator based on organic EO polymer will come in future.