Guided-mode based arbitrary signal switching through an inverse-designed ultra-compact mode switching device.

Abstract

The application of the inverse design method and free-form geometrical optimization in photonic devices endows them with highly tunable functionality and an ultra-compact footprint. In this paper, we implemented this platform to silicon photonic guided-mode manipulation and demonstrated a guided mode-based signal switching architecture. The passive signal switching mechanism is utilized so that no power consumption is needed for routing state maintenance. To solve the explosive increasing design cost in such mechanism when the switching scale is expanded, we illustrate that only a small number of mode switching devices need to be designed as the switching basis. In theory, arbitrary signal routing states can be constructed by cascading some selected basis. The required switching devices can be decreased from factorial N to N - 1 for the N channels switching. For proof of concept, we design and experimentally demonstrate the three-mode cases and the cascade method to combine any three mode-based switching devices. Experiments show that the insertion losses of TE0 - TE1 mode switching unit (U1), TE1 - TE2 mode switching units (U2), and TE0 - TE2 mode switching unit (U3) are less than 2.8 dB, 3.1 dB, and 2.3 dB, respectively. The demonstrated architecture has both arbitrary signal switching capability and ultra-compact footprint, which is promising in the application of mode-division multiplexing communication systems.