Design and fabrication of an optical film for fiber bragg grating external cavity diode lasers
doi:10.37188/CO.EN.2022-0010
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摘要:
腔面光学薄膜是光纤光栅外腔 器(ECL)的关键结构,平面波方法(PWM)被广泛应用于腔面光学薄膜的设计,然而该设计在ECL中的实际应用效果往往并不理想。本文在使用PWM方法时通过时域有限差分法分析其中的原因,并考虑腔面尺寸和结构影响。仿真结果显示,PWM设计存在反射率差和反射曲线偏移等问题,实际的反射特性显著偏离设计值。因此本文重点优化了薄膜设计,并采用磁控溅射工艺镀膜。测量结果显示,优化后增透膜的反射率降低了30%,高反膜反射率增至96%以上,所制备的ECL的光纤输出功率超过650 mW。本文研究结果为ECL和其他半导体光电子器件的腔面光学薄膜研制提供了参考。
Abstract:The cavity surface optical film is one of the most crucial components of the fiber bragg grating External 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 fabricated, and provides a reference for optical films in ECLs and other semiconductor optoelectronic devices.
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Table 1.Structural parameters of the simulation model
Parameter Typical value and range Core layer thickness (Hcore) 0.5 μm/0.05−1 μm Core layer width (Lcore) 1 μm/0.2−2 μm Core layer refractive index (ncore) 3.4902−3.6 Cladding refractive index (nclad) 3.4902 Refractive index difference ($\Delta n$) 3% -
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