Study On High Power Red Laser System Used In Photodynamic Therapy

Photodynamic therapy (PDT) is a new method to treat cancer, has developed rapidly in recent years. Photosensitizer plays an important role in the PDT. The first-generation photosensitizer has low penetrability and broad absorption spectrum to tissue that induce the great side effect. Now research of the second-generation photosensitizer and the related laser source becomes important.In this thesis, the principle and the method of produce 1319nm in Nd:YAG solid laser have been researched, double frequency 1319nm laser we can get a red laser output at 660nm, the frequency of the laser system just locate the absorbing peak of second-generation photosensitizes. The solid-state laser has higher power, higher stability and lower cost than dye laser and laser diode. So it has a great future in the application of PDT.We designed a laser system: the parameters of double ellipse cavity were optimizing analyzed such as coupling efficiency and pump energy distribution. The pulse laser has better curative effect in PDT than CW laser, so AO Q-switch is used. The theory of intracavity frequency-doubled & Q-switched laser has been researched. Three kinds of nonlinear crystals are compared and KTP is selected finally. The phase match parameters and allowable parameters of KTP for 1319nm laser in frequency doubling were calculated. Dynamical resonator and misalignment insensitivity resonator was studied and the optimum resonator was designed.At last, we tested the laser system, obtained 48W output power at 1319nm & 4W output power at 660nm while the current was 26A.