Process Insensitive Broadband Coupler for Optical Coherence Tomography Application

The optical power divider flatness in wavelengths for chip based optical coherence tomography is crucial to higher signal-to-noise ratios. A Mach-Zehnder structure could be utilized to smoothly maximize the splitting ratio of 10:90 on a silicon platform with a 0.2 micrometer of decoupler optical path difference, which is insensitive to the process variation up to 40 nanometers. A point spread function applied on the Mach-Zehnder directional coupler shows at least a 20-dB signal-to-noise ratio improvement in optical coherence tomography applications.