Integrable microwave filter based on a photonic crystal delay line

• Published in: Nature communications Vol. 3; no. 1; p. 1075
• Main Authors: Sancho, Juan, Bourderionnet, Jerome, Lloret, Juan, Combrié, Sylvain, Gasulla, Ivana, Xavier, Stephane, Sales, Salvador, Colman, Pierre, Lehoucq, Gaelle, Dolfi, Daniel, Capmany, José, De Rossi, Alfredo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25.09.2012; Nature Publishing Group
• Subjects: 639/624/1075/1081; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2092

The availability of a tunable delay line with a chip-size footprint is a crucial step towards the full implementation of integrated microwave photonic signal processors. Achieving a large and tunable group delay on a millimetre-sized chip is not trivial. Slow light concepts are an appropriate solution, if propagation losses are kept acceptable. Here we use a low-loss 1.5 mm-long photonic crystal waveguide to demonstrate both notch and band-pass microwave filters that can be tuned over the 0–50-GHz spectral band. The waveguide is capable of generating a controllable delay with limited signal attenuation (total insertion loss below 10 dB when the delay is below 70 ps) and degradation. Owing to the very small footprint of the delay line, a fully integrated device is feasible, also featuring more complex and elaborate filter functions. The flexibility of microwave photonics provides advantages over electronic circuitry, yet the lack of integrated chip-scale devices limits its practical application. This study presents microwave filters based on photonic crystal waveguides with controllable delays as a step towards intregable circuits.