Research On The Infrared Laser And Interaction Of The Laser With Biologic Hard Tissue

The infrared laser, which is safe for eyes, can be strongly absorbed by water. It has the advantage of shallow tissue pierce depth, small damage and high accuracy in laser surgical operation, making it widely applied in the orthopedics, digest, urology and many other medical fields. It is an ideal medical laser. So far, the medical infrared laser, as Tm, Ho laser, has been deeply researched and widely applied abroad. While interiorly, the research, especially the study related to the application, is far from enough. The comprehensive research of the infrared laser, especially aiming at the medical application, can make great improvement to the laser medical treatment.The infrared laser is mainly used for treating or ablating the pathological organization taking advantage of heat effect in medical application. The clinic research indicates that the pulse energy, pulse width and duration time can influence the surgical effect directly. The study of interaction between the laser and biologic tissue, especially the quantitative analysis of the various influence factors, not only offer guidance with choosing the adaptive laser parameters,but also helps to discover new laser medical application , expand the application field and promote the development of the laser medical treatment.The 1.444μm and 2.1μm medical infrared laser and the interaction between laser and the biologic hard tissue have been researched in this dissertation. The main works are as follows:(1) The conditions required for 1.444μm laser output and the ways of restraining autoecious oscillation have been analyzed. The theoretical model of the 1.444μm Nd:YAG laser has been developed firstly considering the multi-wavelength competition. Optical coating requirement of cavity lens and the influence of autoecious oscillation and amplified spontaneous emission to the laser output were studied and experimented. This model can reflect the laser operation rule more precisely and guide to the laser design. The laser output of average power 47W was obtained when the input power is 4kW in the experiment. It can satisfy the laser clinic application and will accelerate the development of medical laser.(2) The absorption spectrum, energy transfer and working characters of the 2.1μm Cr,Tm,Ho:YAG laser have been analyzed in detail. The free pulse and Q switch theoretical model has been built up considering the energy transfer process of the Tm and Ho ions'multi lower levels. The analysis of the laser design and experiment of the laser output have been done. The simulation results are well accord with the experiment results, which indicates that the theoretical model describing the laser operation correctly and offer guidance to the laser design. A maximal single pulse energy of 4.5J and average power of 27W was obtained in the experiment, which reached the leading level abroad and greatly promote the development of the medical laser in out country.The Erbium laser tooth tissue ablation and Holmium laser lithotripsy are two kinds of typical application in medical field of infrared laser. The laser induced thermodynamic micro-explosion of the tissue surface water has the main effect to the tissue ablation. With the multi-material Euler algorithm, the numerical model has been developed, the high pressure shock and thermal deposition to the tissue surface during the micro-explosion process have been calculated quantitatively, and the laser eradiation intensity and water film thickness effect to the shock pressure have been analyzed. This offset the shortage of the former experiment. The calculation result indicates the high energy short pulse laser can make high pressure shock on the tissue surface, which is well accord with the correlative experiments. This indicates the numerical model has applied meaning in laser medical application.