Coupled vertical gratings for applications in wavelength division multiplexing

WDM gratings

SEM Micrograph of fabricated structure

Wavelength division multiplexing (WDM) is a crucial instrument in data and communications networks. Much of today's WDM technology is fiber based. However, extensive research in recent years has gone into exploring silicon on insulator as a viable platform for realizing integrated devices and subsystems. The ability to take advantage of the mature complementary metal oxide semiconductor fabrication infrastructure ensures the cost effectiveness of fabricating on SOI. To realize sophisticated silicon integrated systems for potential applications in data networks, it is necessary to study a major building block of these systems, the wavelength division multiplexer. State of the art integrated WDM technologies include high order ring resonators. However, these filters are usually limited to a free spectral range of around 20nm, which limits the number of channels which may be implemented. The device under study here consists of a coupled vertical grating structure and offers a large free spectral range covering the entire telecommunications band. Consequently, a much larger number of WDM channels may be realized with this approach using coupled vertical gratings. Theoretical and experimental studies show that the device bandwidth and channel location may be tailored according to specific application requirements.

WDM gratings

Transmission spectra of through (red) and drop (blue) ports.


  • K. Ikeda, M. Nezhad, and Y. Fainman, "Wavelength selective coupler with vertical gratings on silicon chip," Appl. Phys. Lett. 92, 201111 (2008).
  • D. T. H. Tan, K. Ikeda, A. Mizrahi, M. Nezhad, and Y. Fainman, "Coupled Vertical Gratings on Silicon for Applications in Wavelength Division Multiplexing," SPIE Photonics West, San Francisco, CA, January 2010. Proc. SPIE, vol. 7607, pp. 760705, February 2010.