The self sum frequency mixing (self-SFM) process is recently recognized as a new way of obtaining blue lasers

that is

summing the fundamental laser generated by a LD and remaining LD light by means of a single nonlinear laser crystal.This kind of scheme can achieve both laser action and nonlinear conversion in one crystal

which results in more compact

robust and manageable devices. A theoretical model for describing the self-SFM laser generation is developed

in which spatial distributions of the pump and fundamental lasers with arbitrary beam waists are fully taken into account.The analysis can be simplified by using the average approximation.The output power of the self-SFM laser is related to many physical parameters such as crystal length

doped ion concentration

pump waist

cavity mode size

walk-off angle

pump power

absorption coefficient at the pump wavelength

phase mismatch and effective nonlinear coefficient.Hence it is necessary to reach a compromise among the above parameters in order to optimize the self-SFM laser output.The model is applied to the self-SFM laser generated by two kinds of crystals of current interest

NYAB and Nd:GdCOB.Their self-SFM laser output properties are theoretically discussed

predicted or verified.The calculated results are compared with the experiments

which shows the validity of our model. Based on the analysis of applying the model to NYAB and Nd:GdCOB

some useful information can be summarized on improving the output power of the self-SFM laser

that is

large effective nonlinear coefficient

small walk-off angle

small internal loss

small phase mismatch

suitable beam waists(pump and fundamental)

appropriate crystal length and ion concentration. The model is not limited to self-SFM lasers and may be applied to general analysis of the laser generation with Gaussian beams

for instance

fundamental oscillation

SFD lasers

intracavity-frequency-doubling lasers and microchip lasers.Particularly

for microchip lasers

the model can be further simplified by assuming that the pump waist and cavity mode size are constant in the gain medium.