Optical isolators allowing unidirectional light transmission are an important building block in photonic computation and communication. Such devices are widely used in optical and photonic circuits and systems, e.g. to control the photon flow on a photonic chip or to prevent light from reflecting back into a laser emitter. Traditional optical isolators are realized with magneto-optical garnets which in a magnetic field induce Faraday rotation to polarized light. This scheme, however, is difficult to implement on an integrated platform due to the challenges in material growth and bulky device footprint. Recently, Prof. Xiankai SUN's research group proposed an ultracompact integrated isolator by exploiting graphene's magneto-optical property on a silicon-on-insulator platform. With CMOS compatibility, this approach features an ultracompact device footprint that is about 200 times smaller than the traditional implementation using magnetic-optical garnets, which has shown great promise for on-chip integration of photonic nonreciprocal components.

This work originally published in Applied Physics Letters as a cover article and Editor's Pick has been selected by Optics & Photonics News (OPN), The Optical Society's monthly news magazine, as one of the world's 30 most clearly communicated breakthroughs in optics in 2016.

Relevant links:
1.      World's 30 most clearly communicated breakthroughs in optics in 2016, Optics & Photonics News, Dec. 2016;
         URL: www.osa-opn.org/optics-in-2016  
2.      Hybrid graphene/silicon integrated optical isolators, Optics & Photonics News, Dec. 2016;
         URL: www.osa-opn.org/home/articles/volume_27/december_2016/extras/hybrid_graphene_silicon_integrated_optical_isolato/
3.      Hybrid graphene/silicon integrated optical isolators with photonic spin–orbit interaction, Appl. Phys. Lett. 108, 151103 (2016); 
         URL: http://dx.doi.org/10.1063/1.4945715
4.      Prof. Xiankai SUN's Photonic and Optomechanical Nanodevice Lab:
         www.ee.cuhk.edu.hk/~xksun/