Spikes

摘要

A spike is an unwanted narrow transmission peak in a rejection region or a sharp unwanted drop in the midst of a reflecting region. Spikes are a frequent feature of extended high-reflectance zones. A very simple form is the spike that automatically appears when two relatively displaced high-reflectance structures are coupled together. This spike, fortunately, is readily eliminated by adjusting the coupling condition. However, spikes that regularly appear in refinement and synthesis of high reflectance structures are more persistent. Adjustment of the target positions rarely reduces them but simply makes them move in wavelength. Thus they are difficult to remove. Since the area beneath the spike is small, in many applications they are simply tolerated. This paper looks at the origins and properties of such spikes and examines why they are such persistent features of broad reflecting structures.