Particle Swarm Optimized Optical Directional Couplers with Ultrasmall Size and Wide Bandwidth

Abstract

Optical directional couplers are the basic components of many optical information devices. The optical directional couplers based on silicon-on-insulator are very attractive due to the low power consumption, high transmission efficiency, and compatibility with complementary metal-oxide-semiconductor fabrication processes. However, the size of couplers designed by traditional ways could not meet the requirements of on-chip integrated optical systems. In this paper, two cross directional optical couplers on silicon-on-insulator are designed by a particle swarm optimized inverse-design method. Benefiting from the large optimization space, the footprint is as small as 2 × 2 μm2, which is much smaller than that of traditional devices. The simulation results show that the coupling efficiency of TE and TM directional couplers reaches 69.1% and 89.7% at 1550 nm, respectively. Both devices could operate in a broad wavelength range of 1480–1570 nm for TE and 1480–1605 nm for TM, and maintain over 60% transmission and over 20 dB crosstalk at the same time. This work may pave the way for ultra-small optical devices and on-chip photonic integrated circuits.