Complete optical isolation created by indirect interband photonic transitions

• Published in: Nature photonics Vol. 3; no. 2; pp. 91 - 94
• Main Authors: Yu, Zongfu, Fan, Shanhui
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2009; Nature Publishing Group
• Subjects: Applied and Technical Physics; Exact sciences and technology; Frequency conversion ; harmonic generation, including high-order harmonic generation; Fundamental areas of phenomenology (including applications); letter; Nonlinear optics; Optics; Physics; Physics and Astronomy; Quantum Physics; Silicon; Optical isolators; Interband transitions; Refractive index; Optical systems; Optical waveguides; Photonics; Nanophotonics; Field distribution; Integrated optoelectronics; Ring resonator; Frequency response; Silicon; Optical frequency conversion; Nonlinear optics
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2008.273

Achieving on-chip optical signal isolation is a fundamental difficulty in integrated photonics 1 . The need to overcome this difficulty is becoming increasingly urgent, especially with the emergence of silicon nano-photonics 2 , 3 , 4 , which promises to create on-chip optical systems at an unprecedented scale of integration. Until now, there have been no techniques that provide complete on-chip signal isolation using materials or processes that are fundamentally compatible with silicon CMOS processes. Based on the effects of photonic transitions 5 , 6 , we show here that a linear, broadband and non-reciprocal isolation can be accomplished by spatial–temporal refractive index modulations that simultaneously impart frequency and wavevector shifts during the photonic transition process. We further show that a non-reciprocal effect can be accomplished in dynamically modulated micrometre-scale ring-resonator structures. This work demonstrates that on-chip isolation can be accomplished with dynamic photonic structures in standard material systems that are widely used for integrated optoelectronic applications. The realization of a chip-based, broadband optical isolator is of considerable interest for integrated photonics. To date, no technique has been shown to be able to do this using materials and processes that are CMOS-compatible. Now, scientists propose that the use of direction-dependent photonic mode transitions in silicon nanophotonic structures could be the solution.