Improved cavity ring-down system for high precision measurement of the specific modes' loss in ring cavity

An improved system for measuring the specific modes’ total loss in high quality ring cavity is presented. The experimental apparatus measuring cavity ring-down signals are described in detail. The specific modes in the passive ring cavity can be obtained by controlling the manually piezoelectric transducer which mounted on the laser cavity mirror. The image of the specific mode was shown on the CCD and its corresponding cavity ring-down signal is obtained when incident laser light was shut off by optical switch. The losses of three specific transverse modes, such as TEM00, TEM01 and TEM10, are measured. The improved system realizes the specific mode real-time monitoring and high precision loss measurement simultaneously when the ring cavity assembling and alignment.