Probing of localized reflections in photonic devices and circuits on InP using an upgraded high precision reflectometer

Summary form only given. The high complexity of present photonic integration technologies on InP necessitates a thorough knowledge of the prominence of reflections in guiding layers as they can profoundly influence the circuit performance. These can originate at spatially localized refractive index discontinuities in the guide and can have several potential sources ranging from the growth- or process-induced defects and component side-walls to such key elements for photonic integration as the butt-joints between active and passive components and the tapered regions for spot-size conversion. The work described in this paper precisely addresses this issue using an upgraded high precision reflectometer in two ways: first, by monitoring and precisely locating reflections in the guiding layer and second, by extracting relevant information on the device performance through a study of reflections and their spectral properties. The high precision reflectometer employed here is basically a Michelson interferometer equipped with two different low-coherence light probes of central wavelength ~1.3 or ~1.55 μm and a spectral half-width of about ~55 nm