Studies On Output Performance Of 3 Micron Band Er-doped Solid State Lasers Pumped By LD

Applications such as medical applications, remote sensing, atmosphere pollution monitoring, and military countermeasures can all benefit from the development of the 2.5-3μm laser sources, especially in situations which need strong absorption by water, and short penetration depths of a few micrometers into biological tissue. When the concentration of Er in the laser media is high, the emission wavelength of the Er doped media is near the 3 microns, which is at the absorption peak areas of water. This paper analyzes the spectrum of the Er doped media near 3 microns, including the 50 at%-doped Er:YAG crystal and the 10 at%-doped Er:YAG ceramic. In addition, the 30 at%-doped Er:YSGG crystal is simply introduced. On this basis, the output performance of the Er:YAG crystal and the Er:YAG ceramic, which are pumped by LD, is studied.Firstly, the physical properties of the Er:YAG crystal are introduced, which is followed by a simple analysis on the energy level structure of Er3+. On this basis, the absorption spectrum and the fluorescence spectrum are calculated to get the absorption cross section and the emission cross section,then the gain cross section and the gain coefficient are also calculated and analyzed. In addition, J-O theory is introduced to calculate the spectrum parameter of the Er:YAG crystal, such as the oscillator strength of electric dipole transition, the probability of spontaneous emission transition, the fluorescence lifetime, the branch ratio of fluorescence and integral emission cross section, etc. It is similar to deal with the Er:YAG ceramic.Secondly, on the basis of heat conduction equation, single-end-pumped columnar thermal analysis models are established to calculate and simulate the temperature distribution in the Er:YAG crystal and the Er:YAG ceramic in theory. Then the stress and the maximum pump power was also analyzed.Lastly, the energy level transition of Er3+ is analyzed and the influence of concentration on the output wavelength is discussed. On this basis, Er solid laser theory model, including the rate equation, is established. Then the influence of concentration is further discussed. After that, the influence of each parameter on output performance of Er:YAG solid state laser is simulated using numerical method. On the basis of completing the theoretical analysis, the cavity is designed and the initial experiment is carried on.With the studies on 3 micron band spectral properties and output performance of singly Er-doped media, it is concluded that the 2.94 microns laser output with high power needs short cavity length, low loss, high reflectivity of output mirror, as well as reducing the heating effect of the laser media or increasing the maximum stress the laser media can withstand. At the same time, the studies also provides the certain reference for other 3 micron band lasers.