An Advantaged Multiple-pass Herriott Cell

A multiple-pass geometry for simple structure and easy adjustment is designed ,which consists of only a concave mirror and a plane mirror. The stability condition of this optical system is worked out. A design procedure for maximum number of reflection is described that includes a consideration of input ray diameter and divergence angle. A 56-pass cell is constructed for Ti: sapphire ring laser photoacoustic spectrometer. The calculated spot pattern is in good agreement with the experimental observation. This technique is useful for photoacoustic spectroscopy and long path absorption.