Magnetically Active Semiconductor Waveguides for Optoelectronic Integration

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Professor Rajeev Ram
Research Laboratory in Electronics, MIT
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Tauhid Zaman
Research Laboratory in Electronics, MIT
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Xiaoyun Guo
Research Laboratory in Electronics, MIT
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Dave Sossen
MIT Technology Licensing Officer
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Magnetically Active Semiconductor Waveguides For Optoelectronic Integration

US Patent 7,130,494
Semiconductor Waveguide Isolators
Journal of Lightwave Technology , 26(2):291-301, Feb. 12, 2008
Faraday Rotation in Magneto-Optical Semiconductor Waveguides for Integrated Isolators
Proceedings of SPIE 6124, Optoelectronic Integrated Circuits VIII, pp. 612416-7, Mar. 3, 2006


  • Optoelectronic integration for devices such as lasers and optical amplifiers
  • Large scale photonic integrated circuits

Problem Addressed

Optical isolators are widely used to isolate active optoelectronic components, such as lasers, from unwanted optical feedback. However, current optical isolators utilize bulk magneto-optical materials, birefringent crystals, or bulk optical polarizers. These bulk optical components are constructed from non-semiconductor materials, and consequently cannot be easily integrated with semiconductor lasers or optical amplifiers, which obstruct the development of large scale photonic integrated circuits.


The invention is a magnetically active semiconductor (MaSC) waveguide, which enables the monolithic integration of optical isolators and circulators with semiconductor optoelectronic devices. By using select atoms and particles, the magneto-optical activity of the semiconductor is enhanced while the optical loss is reduced, thereby enabling the fabrication of novel semiconductor waveguide devices. The MaSC alloys can be fabricated in a range of bandgap energies and refractive indices so that the resulting waveguides can guide beams of light for an extended period of time. Guiding light close to magnetically doped semiconductor alloys can dramatically enhance the alloy’s polarization rotation, thereby leading to the development of fully integrated isolators and circulators.


  • MaSC designed to possess large magneto-optical activity with low optical loss
  • MaSC alloys fabricated in a range of bandgap energies and refractive indices
  • Dramatically enhanced polarization rotation possible due to flexible MaSC fabrication
  • Monolithic integration of optical isolators with optoelectronic and electronic components enables large scale photonic integration