Optimal design of a 4  ×  4 MMI thermal optical switch with trapezoidal air trenches

Optical switches are important in signal routing and switching. In this paper, a thermal optical switch with trapezoidal air trenches is proposed. The proposed structure consists of two cascaded 4×4 multimode interference (MMI) couplers. The beam propagation method is used to optimize the dimension and analyze the characteristics. Simulation results show excess loss (EL) and insertion loss (IL) are less than 0.14 dB and 0.22 dB at the wavelength of 1550 nm, respectively. Besides, the extinction ratio (ER) is higher than 21 dB. This design has the advantages of small size, low loss, and high flexibility, which is promising for application to all-optical network routing.