Study on contamination problem in cavity enhanced breath gas diagnosis technology

Cavity ring-down or cavity enhanced expiratory gas diagnosis is a promising technology direction in medical diagnosis, which is expected to solve the problems of rapid, accurate, non-invasive and low-cost diagnosis of some diseases. The core of these techniques for breath gas diagnosis is to use the optical resonance’s enhancement effect to increase the interaction path between laser and breathing gas, so as to improve the detection sensitivity of breathing mark gas concentration. However, in the clinical application of this kind of technology, breathing gas needs to be filled with an ultra-low loss optical resonator. In this process, the pollution of optical resonator becomes an important bottleneck that affects and restricts the development of this technology. In this paper, different from the traditional way of gas pretreatment, the ideas to solve this problem are discussed and analyzed from the perspectives of pollution discovery, structure optimization, pollution immunity design, etc. Especially, focusing on the spectral ripple effect in the optical feedback cavity enhancement system, the optimization of V-shaped cavity structure and the aerodynamic design of cavity structure, the cavity pollution problem of V-shaped cavity is discussed and analyzed. These works hope to provide some references for accelerating the clinical application of this technology.