A 2 × 2 switch based on differential effective thermo-optic (TO) coefficients of waveguide supermodes is proposed and experimentally demonstrated as a more compact alternative to Mach-Zehnder interferometer (MZI)-based switches used in coherent photonic matrix processing networks. The total waveguide width of the device is 1.335 μm. Using a novel, to the best of our knowledge, supermode coupler with a wideband 3-dB coupling ratio, the switch was engineered to have on-off extinction ratios (ERs) ranging from 24.1 to 38.9 dB for the two output ports over a 135 nm bandwidth. Insertion losses (ILs) of less than 0.3 and 0.4 dB over the 100 nm bandwidth were measured for bar and cross transmission, respectively. The waveguide width error tolerance is +/-30 nm. The proposed device has the potential to improve the scalability of a programmable coherent mesh for matrix processing by increasing the integration density without sacrificing the overall accuracy or limiting the operational wavelength range of the mesh.