Necessity of metallic reflective coatings
The transmission efficiency is almost the same with or without reflective coating. We measured the reflectance of a SILICAGRIN “LEC” (Lateral Emitting Collimator) with and without a metallic (Au) reflective coating deposited on the tip, using the optical power shown in Figure [A] below as a reference (100%).
TE (Transmitting Efficiency (%)) = PS1,2 /Po (output) x 100
When we compared [A], [B], and [C] on the left using the above formula, [B] and [C] were almost the same. However, [B] is expensive due to the materials and process required. If the fiber tip is immersed in liquid, you should choose [B] for stable reflection. However, in a dry environment, if cost is a major concern, [C] is sufficient for practical use.