Study Of Measuring Method Of Transverse Mode Configuration In Diode Pumped Solid State Laser

By definition, transverse mode is the stable field distribution of photoelectric magnetic field within the resonant cavity in the direction that is perpendicular to the propagation direction of the laser beam. The evaluation parameters on laser beam quality include focused spot size, far-filed divergence angle, Strehl rate, energy circle rate, times diffraction limited factorβand laser beam quality M~2 factor, etc. All these parameters are comprehensive evaluation for the laser beam in different ways, in fact, the primary factor, which fundamentally decides the laser beam quality, is the configuration of multiple transverse modes in a laser beam. All the measuring methods of the evaluation parameters on laser beam quality are based on the analysis of the transverse mode in a laser beam. By laser design requirement, the analysis of the transverse mode in a laser beam is a research technique which is instructive and meaningful for achieving the transverse mode design target and acquiring good laser beam quality in laser design. There are various kinds of laser beam models including Hermite-Gaussian beam, Laguerre-Gaussian beam, multiple modes Gaussian beam, Gaussian-Shell beam, flattened Gaussian beam and wave front distortion beam, etc. In this thesis, Laguerre-Gaussian beam is used as the laser beam model, and the measuring of the transverse mode proportion for this kind of laser beam is developed. A new measuring method of transverse mode configuration in a laser beam is presented. It is based on the spatial relative intensity distribution of laser field. Firstly,an equation for spatial relative intensity distribution of laser field and transverse mode proportion is built. Then transverse mode proportion is derived by measuring the spatial distribution curve of laser field. Finally, transverse mode configuration is obtained. This new measuring method is feasible in application and valuable for laser design, promoting the performance and mode control in a laser. It is possible to realize the real-time measurement of transverse mode configuration in a laser beam by increasing the measuring speed and improving the measuring accuracy of the spatial distribution curve of laser field.