Alignment Tolerant Couplers for Silicon Photonics


Laser integration, optical coupling and assembly are challenging problems that need to be further addressed to reduce the manufacturing costs of silicon photonics based products. In this paper, we propose novel coupling devices that facilitate the passive assembly of silicon photonics chips with laser diodes and optical fibers by means of pick-and-place tools by relaxing the stringent alignment tolerances required for maintaining a high coupling efficiency. In these devices a lateral misalignment of the laser or fiber relative to the chip is accommodated by a varying phase difference between two on- chip single mode SOI waveguides to which the light is coupled with minimal insertion loss penalty and a balanced power splitting. This device concept is successfully applied to the fabrication of in-plane laser couplers based on inverse taper arrays and out-of-plane fiber couplers with diffraction gratings. Furthermore, we experimentally demonstrate the suitability of the proposed devices for fiber array assembly in Mach-Zehnder interferometer configuration. The best devices exhibit a three- fold improvement relative to the lateral alignment tolerances of conventional couplers.


S. Romero-García, B. Shen, F. Merget, B. Marzban, J. Witzens, “Alignment Tolerant Couplers for Silicon Photonics,” IEEE J. Sel. Top. Quant. Electron. 21(6), Art. 8200214 (2015).