| In this project, polarization insensitive optical switch matrices based on semiconductor optical amplifiers were designed, fabricated, and tested.; First, several types of optical switch architectures, which are monolithically integrated and completely non-blocking, have been examined to determine the structure which provides better performance, and also the corresponding chip size, signal-to-noise ratio, and number of amplifiers have been calculated. According to our investigation, the Clos and the square array architectures appear to be the best candidates for large-scale semiconductor optical switch matrices.; The passive and the active structures of the optical switches were designed. In the passive structure design, light wave propagations in straight dielectric waveguides and waveguide bends were simulated by solving Maxwell's equation with the finite-difference method. To realize the polarization insensitive optical switches, polarization insensitive semiconductor optical amplifiers using strained multi-quantum wells as active layers were designed. In unstrained quantum well structures, the gain is inherently polarization sensitive, which implies that the gain for TE polarization is much higher than that for TM polarization. To equalize the gains for TE and TM polarizations, the strained quantum wells were used as the active layers. In designing the strained quantum well structure, several different approaches have been investigated, and for each approach, energy band structures and gain spectra in III-V compound material based strained quantum wells were calculated by solving Schodinger equation with the eight band k{dollar}cdot{dollar}p model. The polarization gain equalization for this project was obtained by the introduction of a small amount of tensile strain in each of the quantum wells.; The designed optical amplifiers and switch matrices (2 x 2, 4 x 4, and 8 x 8) were fabricated and tested. 8 dB net gain was achieved for TE polarization in 350 {dollar}mu{dollar}m long amplifiers at 100 mA driving current and the difference between TE and TM polarization gains was 2.2 dB. The switching operation of the fabricated switches was observed, and the extinction ratio of the switch in the shortest path was 49 dB. |
