Parallel Deviation of Concave Mirrors in Herriott Multipass Cells

Reflection spot patterns changes has been analysed both theoreticallly and numerically based on matrix optics and combinatorics when there is some parallel deviation between the two concave mirorrs of a Herriott multipass cell. The results show that, with a fixed inlet spot location of the incident light, the reflection spots can still distribute in a same circle by adjust the incidence angle even for non-parallel mirorrs of a Herriott multipass cell. With increasing parallel deviation between the two reflection mororrs, the circle radius increases, and center of the circular path is no longer located at the center of the reflection mirorr, it is farther and farther from the center of the reflection mirorr. These characteristics help us determine whether there is parallel deviation between the two concave reflection mirorrs and to judge its relative magnitude. It can be served as a guide for optical path adjustment in Herriott multipass experiment.