The design and simulation of a novel ring multi-pass optical cell for detection of environmental trace gas

Abstract

A ring multi-pass optical cell which consists of three spherical mirrors to form a ring cell has been proposed to achieve a long path length in compact volumes. As with the astigmatic multi-pass optical cell, the dense beam spot pattern from the ring multi-pass optical cell more evenly fills the interior surface of the spherical mirror. The disadvantage of the astigmatic cell is that it requires extremely high-precision mirrors to ensure that the pattern will close. However, with the ring multi-pass optical cell, adjusting the inclination angle of spherical mirrors can make up for errors of the mirrors, and the self-consistent condition always can be established. The desirable patterns are based on the given base length, the inclination angle of spherical mirrors, the coupling window from the optical axis and the incident angle of the beam. In consideration of the astigmatism of the off-axis mirror, the matrix optics is employed in describing and analyzing the behaviors of the ring multi-pass optical cell. The new ring multi-pass cell presented in the paper achieves a 120 m optical path length in a volume of 717 cm3. The optical simulation based on the ABCD matrix and optical software shows the validity and the usefulness of the techniques proposed.