A switching device includes a substrate, a first waveguide segment, a second waveguide segment, a heating device, a liquid, and a pressure controlling mechanism. The substrate is coupled to the first waveguide segment and the second waveguide segment, and the substrate includes a chamber that separates the first waveguide segment from the second waveguide segment. The liquid is disposed in the chamber and is responsive to the heating device. The pressure controlling mechanism controls a pressure in the chamber such that inadvertent bubbles are prevented from forming between the first waveguide segment and the second waveguide segment.