@article { Shi:13, title = {Silicon photonic grating-assisted, contra-directional couplers}, journal = {Opt. Express}, volume = {21}, number = {3}, year = {2013}, month = {02/2013}, pages = {3633--3650}, publisher = {OSA}, type = {article}, abstract = {We demonstrate, in both theory and experiment, 4-port, electrically tunable photonic filters using silicon contra-directional couplers (contra-DCs) with uniform and phase-shifted waveguide Bragg gratings. Numerical analysis, including both intra- and inter-waveguide couplings, is performed using coupled-mode theory and the transfer-matrix method. The contra-DC devices were fabricated by a CMOS-photonics manufacturing foundry and are electrically tunable using free-carrier injection. A 4-port, grating-based photonic resonator has been obtained using the phase-shifted contra-DC, showing a resonant peak with a 3-dB bandwidth of 0.2 nm and an extinction ratio of 24 dB. These contra-DC devices enable on-chip integration of Bragg-grating-defined functions without using circulators and have great potential for applications such as wavelength-division multiplexing networks and optical signal processing.}, keywords = {Gratings; Phase shift; Integrated optics devices; Optical resonators; Optical switching devices}, URL = {http://www.opticsexpress.org/abstract.cfm?URI=oe-21-3-3633}, author = {Wei Shi and Xu Wang and Charlie Lin and Han Yun and Yang Liu and Tom Baehr-Jones and Michael Hochberg and Nicolas A. F. Jaeger and Lukas Chrostowski } }