The Study On The Thermal Interaction Comparison Of High Power Semiconductor Laser On Biological Tissue

In the wake of the swift development of light electron technique, the semiconductor laser instrument is as one kind of significant light electron device. The extensive use is correspond to the optical fiber,information storage,laser printer,territory such as light calculation,medical treatment and so on. Particularly the application of laser in medical treatment is the earliest and active field. Laser apparatus may be divided into solid laser,gas laser,liquid,laser diode . It has the remarkable advantages of smaller volume, high power of out put, the easy control, dispense with water-cooling, lighter weight and so on. Laser has a wide application in medical treatment field. Such as in ophthalmology, the body of rectification, dermatology, tumour, dentistry, gynaecology, urology, common chirurgery and so on. From on one hand this dissertation was introduced the characteristics of high power semiconductor laser array and its got-up arts and crafts. From on other hand this dissertation studied the experiment which two kinds of wavelength of lasers acted on several biological tissues.This dissertation mostly aimed at high power semiconductor laser array, so the chapter two firstly expatiated that the basic theory of work and then detailedly introduced all kinds of structure of high power semiconductor laser. Specially introduced the structure of high power semiconductor laser array.Then this dissertation introduced the characteristics of high power semiconductor laser array during work. Here we took the high power semiconductor laser array which emit laser whose wavelength is 808nm for example. Including its p-I curve and spectrogram. Here look at the picture 1:Picture 1 semiconductor laser p-I curveWe studied the semiconductor laser whose wavelength is 808nm. Moreover it is discussed that high power semiconductor laser array and it coupled with fiber. By counting we got the efficiency of coupling was 75.1%. After coupling we compared with it's out put P-I curve , and got better the relationship of linearity. Finally we introduced the facture and flow chart of high power semiconductor laser array. Firstly grew on substrate being living in the way of MOCVD's technique, such the component composition all repress the composition in the interest of the long-shaped separately limit of oxide. Secondly we employ the means spattering to be living superficial deposit of wafer one tier of SiO 2 , afterward employing criterion light engraves that technique is living that the superficial etch of SiO 2 comees out long-shaped window. Epitaxial wafer P's side deposit TiPtAu is living, and reduce slightly, and living the compound metal, filming in cavity (altogether cavity the reflectance is 15%and95%separately). The cleavage is sum up the survey, and select out semiconductor core P admittedly stably is living to evaporate in the heat sink. Preparation into laser array and seal. Because thestructure of high power semiconductor laser array whose emits the wavelength is 980nm is different from the structure of high power semiconductor laser array whose emits the wavelength is 808nm, we also introduced the structure of high power semiconductor laser diode whose wavelength is 980nm.When laser acted on biological tissue, it would appear all kinds of changes. Because the wavelength of laser from high power semiconductor laser belongs to infrared area, the action on biological tissue most is thermal interaction. The laser on biological tissue has a lot of interactions, which depend on temperature on biological tissue or the power of peak value. These interactions are coagulation, vaporization, carbonization, melting.Among these interactions, temperature is one important parameter. Here we bases on Vasillev model and introduced one heat transfer model which is the same with high power laser. At the same time we gave some hypothesis which is equal to ideal model. We use the biological tissue which is separated from living body, so ignore the heat fountain of metabolism and blood stream of rate. Depend on the equation of biological transport, we establish math model of heat transport:From above expression, T is temperate in tissue; x is the cursor along the direction of beam of laser;τis time;ρ1 is the density of charcoal layer which is a more hole medium;λ1 is a modulus of heat transportation in charcoal layer; c1 is the specific heat contain in charcoal layer; x1 is the numerical value incoordinate between the air and charcoal layer;ρ2is the density of biological tissue;λ2is the modulus of heat transportation in biological tissue; c 2is the specific heat contain in biological tissue; x 2 is the numerical value in coordinate between the charcoal layer and biological tissue. Based on correlative equations, by using the computer , we can the relationship of two interfacial velocity.Finally this dissertation studied the coagulation interaction by irradiation of laser on biological tissue. We took egg white, chicken, porky as swatches in order to make sure whose effect is better. They are high power semiconductor laser array whose wavelength one is 980nm , the other is 808nm. Firstly irradiate on egg white and then observe whose coagulation interaction is better one. The average diameter is 3.26mm, which is irradiated by 980nm semiconductor laser. But there is no any change on the egg white which is irradiated by 808nm semiconductor laser. So we got that 808nm semiconductor laser can not send out enough heat to make the egg white coagulated. Secondly through an experiment to find out absorptivity in water and albuminoid. Obviously 980nm semiconductor laser has better absorptivity in water and albuminoid. And then irradiated on chicken and pork in order to study their different time of coagulation. Experiments improved that the time of coagulation of 980nm semiconductor laser is more than the time of coagulation of 808nm semiconductor laser. It is about 3to 6 times. Through experiments we can find that the absorptivity to water is not the only one important factor but the color in biological tissue is another important one. It took more time to laser coagulate in biological tissue whose color is more deep than others. Of course there are more factors effect coagulation in biological such as blood vessel in biological tissue and so on.