Novel optical devices based on the tunable refractive index of magnetic fluid and their characteristics

► Magnetic fluid is a new type of functional material, which has many unique optical properties. ► We summarize the tunable refractive index property and the related optical devices. ► Refractive index can be easily controlled by external magnetic field, temperature and so on. ► There are many applications in the field of optical communication and sensing technology. ► New method, structure, and material to improve the response time should be found in the future.