Design and fabrication of an optical film for fiber bragg grating external cavity diode lasers

The cavity surface optical film is one of the most crucial components of the fiber bragg grating Ex-ternal Cavity diode Laser (ECL). Although, the Plane Wave Method (PWM) is widely used in the optical film preparation, it is not an ideal design method when applied in ECL preparation. The Finite-Difference Time-Domain (FDTD) method is used to analyze this problem by taking the effect of facet dimensions and structure into account. According to the simulation, PWM suffers from poor reflectivity and deviation of the reflection curve, which significantly affects performance. Therefore, the optical film design is optimized and verified by experiments. Magnetron sputtering is used to fabricate the optical film, which is then applied to ECL. The measurement results show that the reflectivity of Anti-Reflection (AR) film is reduced by 30% after optimization, while the reflectivity of High-Reflection (HR) film increased to 96%. The prepared ECL's fiber output power exceeds 650 mW. In this paper, the optical film suitable for ECL is designed and fabric-ated, and provides a reference for optical films in ECLs and other semiconductor optoelectronic devices.