Integrated mid-infrared devices including (i) straight/bent waveguides and (ii) directional couplers are demonstrated on silicon nitride (SiN) thin films prepared by optimized low-pressure chemical vapor deposition. The deposited SiN film has a broad spectral transparency from visible up to a wavelength of =8.5m (as seen from Fourier transform infrared spectroscopy). Our SiN waveguide shows a dominant fundamental mode with an optical loss of 2.1dB/cm at =3.7m. In addition, we demonstrate an efficient SiN directional coupler between =3.55m to =3.75m where an 8dB extinction ratio is achieved within each channel upon wavelength scanning. With the inherent advantage of complementary metaloxidesemiconductor compatibility, our SiN platform paves the way to create sophisticated photonic circuits that are desired for mid-infrared nonlinear light generation and chip-scale biochemical sensors.
