The Electro-optical Modulator Based On SOI Rib Waveguide Racetrack Resonator

With the rapid development of the optical communication technology, the integrated optical interconnection network with high-density integration, high reliability, intelligence and decreasing cost has become one crucial direction of the optical communication systems. It is an irresistible trend for optical inter connection replacing the electrical interconnection. Solving the limitation of the Moore’s Law, photonic devices possess more transmission quantity and higher transmission speed with lower power consumption and without frequency crosstalk. Besides, photonic devices have become highlights because they can guarantee the density of remote interconnection and the accuracy of data transmission, while realizing large-scale integration with ultra-small footprint. Silicon-on-Insulator (SOI) material is beneficial to fabricate ultra-small footprint devices because of its high refractive index difference, strong confinement of optical filed and low waveguide bending loss. Moreover, SOI material is compatible with the CMOS process, which means the ultra-small photonic devices can be highly integrated and mass produced based on the SOI material. The optical resonator based on SOI material is widely used as important elements of integrated optical interconnection networks, such as, filters, optical switches, modulators, detectors and so on. However, the research on race-track resonator electro-optical modulator is relatively less concerned. Therefore, this paper has developed an electro-optical modulator based on SOI rib waveguide race-track resonator, which fully takes advantage of the long coupling region of the race-track resonator and effectively promotes the extinction ratio, modulation depth and rate of the modulator.In this work, the single mode of rib waveguide and the optical field propagation within the race-track resonator were simulated by Rsoft and FDTD software, respectively. The resonance and the mode splitting characteristics of the race-track resonator were analyzed, based on which the optical structures were designed. The conductive mechanism of the P-I-N junction and the plasma dispersion effect were analyzed, thus, the interrelation between the carrier concentration changes and refractive index coefficient changes was confirmed. The electrical structure parameters of modulator were determined after the I-V characteristic of the P-I-N junction was simulated via Silvico TCAD software. Utilizing the MEMS process, the integral device of electro-optical modulator based on SOI rib waveguide race-track resonator was fabricated with the designed parameters. After the testing, it is demonstrated that the race-track resonator and the modulator based on performance well. With further analyzing, it is obvious that the mode splitting characteristic of the race-track resonator can be detected and it indeed promotes the performances of the modulator effectively, such as extinction ratio, modulation depth and rate. More specific, when the modulation frequency is1MHz, the extinction ratio is6.99dB, the modulation depth is80%, rising time is29ns and falling time is67ns for race-track resonator modulator, while the extinction ratio is1.52dB, the modulation depth is36%, rising time is41ns and falling time is72ns for ring resonator modulator. The experiment results indicate that the mode splitting of the race-track resonator is beneficial to the modulator as well as other applications of the optical resonators and provides a new idea for the design, although the modulator did not performance ideally.