Thermally Modulated Slow Light in Magnetic Fluid Photonic Crystal

Magnetic fluid is a new type of optical functional material. When it is made as a film, a hexagonal order structure can be formed under an external magnetic field. This novel magnetic-field dependent structure may be regarded as a kind of magnetic fluid photonic crystal. The slow light property in the magnetic fluid photonic crystal was studied in this letter. It was pointed that the geometry parameters of the structure could be tuned by changing the applied temperature. In addition, photonic bandgap and group velocity as a function of temperature were simulated. The results showed that the upper and lower normalized frequency of the photonic bandgap would both shift to higher frequencies, and the maximal group velocity <;0.25 c was obtained, which could be thermally tuned in a large range. The working frequency corresponding to the maximal group velocity would change from 0.2063 to 0.4312 (a/λ) when the external temperature was increased from 18 °C to 48 °C. These results fully proved that the magnetic fluid photonic crystal, as a type of thermally modulated photonic crystal, could be used in the field of optical sensors. It also provided a new idea for generating slow light in colloid photonic crystal waveguide.