Magnetless circulators based on cobalt ferrite films for optical communication systems

• Grant number: 22/02391-6
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Effective date (Start): February 01, 2023
• Effective date (End): January 31, 2024
• Field of knowledge: Engineering - Electrical Engineering - Telecommunications
• Principal Investigator: Hugo Enrique Hernández Figueroa
• Grantee: Gianni Masaki Tanaka Portela
• Supervisor: Yuya Shoji
• Host Institution: Faculdade de Engenharia Elétrica e de Computação (FEEC). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Research place: Tokyo Institute of Technology, Japan
• Associated to the scholarship: 19/13667-0 - Optical circulators based on iron garnets without external magnetization, BP.PD

Abstract

Circulators play a key role in the protection of signal sources, like LASERs and amplifiers, against the harmful effects related to parasitic reflections created by unmatched loads in communication systems. Most circulator designs rely on the utilization of magneto-optical (MO) materials, since such materials can provide the time reversal symmetry breaking required for the operation of circulators. An external DC magnetic field is required for the magnetization of the MO material used in a circulator design, since such materials can be very lossy when not magnetized. One of the main challenges for the design of compact circulators suitable for utilization in optical communication systems with high integration density is related to the magnetization circuit of the employed MO materials. Such magnetization circuits are based on permanent magnets or electromagnets, which in turn are often bulky and complicate the design of circulators with reduced dimensions. We suggest in this project the utilization of a new magneto-optical material known as cobalt ferrite (CFO) in the design of magnetless optical circulators. CFO films are characterized by a strong remanent magnetization, that is, their magnetization can remain very high even in the absence of an external DC magnetic field, and the specific Faraday rotation coefficient of CFO is much higher when compared to conventional garnet ferrites. The design of circulators with reduced footprint can benefit from these two features of CFO films and we will develop at least 1 magnetless three- or four-port optical circulator based on the utilization of such material. (AU)