Chinese scholars integrate non-magnetic optical isolators on silicon nitride optical chips for the first time, helping to advance the future of the quantum Internet(2)

Chinese scholars integrate non-magnetic optical isolators on silicon nitride optical chips for the first time, helping to advance the future of the quantum Internet(2)

2022-05-24 13:35:37 10


"In the course of our research, we have carefully investigated and studied many previous solutions for the implementation of optical isolators, for example, based on the Faraday effect, optical force systems, nonlinear systems, and even the Doppler effect using atomic system synthesis. Many of these outstanding results came from Chinese scholars and teachers. Through our communication and discussion with them, we have also deepened our understanding of the subject matter. Compared to previous work, our work is characterized by high integration, miniaturization, and the overall device is completely controlled electrically." Liu Junqiu explained to.

In summary, the advantages of the optical isolator developed by the team over other experimental methods are: 1) no external magnetic field and magneto-optical materials are required, greatly simplifying the processing process; 2) the combination of a more mature industrial aluminum nitride process, compatible with traditional semiconductor processes, can be integrated on a large scale, reducing costs; 3) the optical waveguide is built on a mature silicon nitride waveguide, with a very low optical loss 4) the device works with only the electrical drive of RF waves, which is a mature technology and low power consumption; 5) as the overall technology combines mature MEMS and integrated optics, the process can be directly applied in commercial-level semiconductor process lines. The devices can be directly integrated with existing optical chip systems.

Future-proof applications: quantum optical interconnection networks

Optical isolators can first be integrated at the exit of a semiconductor laser to prevent reflected light from perturbing the laser. With the rise of quantum technology in recent years, the use of optical fiber communication to transmit quantum information to build large-scale quantum optical interconnection networks has gained widespread attention. The team's efficient acousto-optical modulation can be used to load quantum information at microwave frequencies onto optical carriers for long-distance transmission.

 To protect quantum information from interference as much as possible, such devices often operate in an ultra-low-temperature, low-noise environment, which can be disrupted by any reflected light. This is where we need optical isolators to isolate the reflected light and thus reduce noise.

"Traditional magneto-optical isolators are first of all larger in size and not suitable for placing in large quantities in ultra-low temperature cryogenic cavities. And the applied magnetic field can interfere with the operation of the quantum bits. The integrated optical isolator we have developed can well avoid these problems and is expected to be applied in the near future to build a quantum Internet for computing and transmission of quantum information." Tian Hao said when talking about the future application of the technology.


The results were published on October 21 in Nature Photonics, one of the top journals in optics, under the title Magnetic-FreeSilicon Nitride Integrated Optical Isolator, and have gained widespread attention in both MEMS and optics. Hao Tian, a PhD student in electrical and computer engineering at Purdue University, and Junqiu Liu, PhD, at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, are co-first authors of the article, and Tobias J. Kippenberg, a professor at EPFL, and Sunil A. Bhave, a professor in the department of electrical and computer engineering at Purdue, are co-corresponding authors. The work also won the best student paper award at the IEEE MEMS International Conference 2021 and was selected for the CLEO postdeadline conference presentation at the International Conference on Optics 2021.

Three years of trial and error

Hao Tian received his undergraduate degree in Optoelectronics Technology from Tianjin University and Nankai University, which provided him with a solid foundation in optoelectronics theory and experimentation. With the financial support of Tianjin University, Tian Hao was given the opportunity to study at MIT during his undergraduate studies. Influenced by Professor Jurgen Michel, a senior scientist at MIT's Microphotonics Research Center, and Dr. Lin Zhang, now a professor at Tianjin University, Hao Tian was fascinated by the mechanical interactions of photons with micro and nano structures. During his PhD, he studied under Prof. Sunil Bhave at Purdue University, further investigated the mysteries of photon-phonon interactions, and was fortunate enough to work with Prof. Tobias Kippenberg, one of the founders of the field of photomechanics, and his team.



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