2$\,\times\,$2 Polymer Thermo-Optic Digital Optical Switch Using Total-Internal-Reflection in Bend-Free Waveguides

We present a novel 2 × 2 polymer thermo-optic digital optical switch (DOS) using the total-internal-reflection (TIR) effect. The switch consists of four 1 × 2 TIR-DOSs cascaded with each other. These TIR-DOSs have two branched multimode waveguides and an offset heater electrode in the branched region. Our switch does not have any bent waveguides, and has tapered waveguides and single-mode waveguides only in the input-output fiber coupling region. The fabricated 2 × 2 TIR-DOSs exhibit excellent properties, with very low insertion losses of <; 1.4 dB and switching isolations of >; 50 dB in both turned-off and turned-on states.