Silicon-on-Insulator Microring Add-Drop Filters With Free Spectral Ranges Over 30 nm

We demonstrate highly compact optical add-drop filters based on silicon-on-insulator microring resonators. The microring resonators have a small radius of 2.5 mum and a very large free spectral range ~ 32 nm at the 1.55 mum communication band. The propagation loss in such small micoring resonators was experimentally determined and shown to be extremely important in designing microring add-drop filters with low add-drop crosstalk, low drop loss, and maximally flat drop passband. For box-like channel dropping responses, second-order optical add-drop filters with two coupled microring resonators are designed and demonstrated, and the simulation matches well with the experiment. Devices were patterned with electron-beam lithography. Two fabrication procedures utilizing different polarity of resists were introduced and compared, and the process with negative resist resulted in much smaller sidewall roughness of waveguides, thus reducing the propagation loss in microring resonators.

[1]  S. Xiao,et al.  Modeling and measurement of losses in silicon-on-insulator resonators and bends. , 2007, Optics express.

[2]  L C Kimerling,et al.  Fabrication of ultralow-loss Si/SiO(2) waveguides by roughness reduction. , 2001, Optics letters.

[3]  Y. Vlasov,et al.  Losses in single-mode silicon-on-insulator strip waveguides and bends. , 2004, Optics express.

[4]  Michael Watts,et al.  Coupling-induced resonance frequency shifts in coupled dielectric multi-cavity filters. , 2006, Optics express.

[5]  W. Henschel,et al.  Asymmetrically coupled silicon-on-insulator microring resonators for compact add-drop multiplexers , 2003, IEEE Photonics Technology Letters.

[6]  Tymon Barwicz,et al.  Multistage high-order microring-resonator add-drop filters. , 2006, Optics letters.

[7]  S. Xiao,et al.  Multiple-channel silicon micro-resonator based filters for WDM applications. , 2007, Optics express.

[8]  Tymon Barwicz,et al.  Transparent wavelength switching of resonant filters , 2007 .

[9]  T. Barwicz,et al.  Fabrication of add-drop filters based on frequency-matched microring resonators , 2006, Journal of Lightwave Technology.

[10]  D. Van Thourhout,et al.  Low-loss SOI photonic wires and ring resonators fabricated with deep UV lithography , 2004, IEEE Photonics Technology Letters.

[11]  E. R. Thoen,et al.  Ultra-compact Si-SiO2 microring resonator optical channel dropping filters , 1998, IEEE Photonics Technology Letters.

[12]  H. Haus,et al.  Microring resonator channel dropping filters , 1997 .