1 × 2 mode-independent polymeric thermo-optic switch based on a Mach-Zehnder interferometer with a multimode interferometer.

We present the design and performances of a broadband 1 × 2 mode-independent thermo-optic (TO) switch based on Mach-Zehnder interferometer (MZI) with multimode interferometer (MMI). The MZI adopts a Y-branch structure as the 3-dB power splitter and a MMI as the coupler, which are designed to be insensitive to the guided modes. By optimizing the structural parameters of the waveguides, mode-independent transmission and switching functions for E and E modes can be implemented in the C + L band, and the mode content of the outputs is the same as the mode content of the inputs. We proved the working principle of our design based on polymer platform, which was fabricated by using ultraviolet lithography and wet-etching methods. The transmission characteristics for E and E modes were also analyzed. With the driving power of 5.9 mW, the measured extinction ratios of the switch for E and E modes are larger than 13.3 dB and 13.1 dB, respectively, over a wavelength range of 1530 nm to 1610 nm. The insertion losses of the device are 11.7 dB and 14.2 dB for E and E modes, respectively, at 1550 nm wavelength. The switching times of the device are less than 840 µs. The presented mode-independent switch can be applied in reconfigurable mode-division multiplexing systems.