Extremely Low-Profile Single Mode Fiber Array Coupler Suitable for Silicon Photonics

We report a novel, single mode optical fiber array coupler that couples the single mode fibers (SMFs) with grating couplers (GCs) on a silicon photonics chip and has D-shaped (DS) fibers. This DS fiber array coupler has obliquely polished tips of the SMFs that are fixed on a V-grooved glass, and a mirror plate is put on the polished tip surface of the fiber array coupler. Light that advances in the SMF is reflected by the mirror plate. The reflected light advances through the side face of the SMF, and couples with the GC on the silicon photonics chip. In the vicinity of the obliquely polished tips, the side face of the clad of the SMF is ground in such a way that the cross section of the SMF is formed into a D-shape to get good optical coupling with the GC. The DS fiber array coupler has extremely low-profile of 1.5 millimeters height above the silicon photonics chip surface. We fabricated the DS fiber array coupler, and measured coupling losses between this fiber array coupler and the GCs. The averaged additional optical coupling loss of 0.2dB due to the reflection structure is obtained for 93 coupling interfaces in the 11 fiber array couplers.