This study demonstrates hysteresis loop and pattern formation in a Nd:YVO4 laser at 1064nm (4F3/2 →4I1 1/2) and 1342nm (4F3/2→4I13/2) with an intracavity electro-optic periodically poled lithium niobate (EO PPLN) Bragg modulator by using a T-type cavity configuration. Based on these dual wavelengths sharing population inversion in the same upper energy level to lase, the transmission, Tp, of EO PPLN was chosen as the controlling parameter to explore the dynamics of dualwavelength competition. A hysteresis loop occurred when the extracting efficiencies of dual wavelength were near equivalent. When the pump power was 9.0 W, the hysteresis loop was observed in the region of the transmission of PPLN between Tp=64.88% to Tp=84.47%. The slope efficiencies were 25.96 and 3.92% and the thresholds were 2.5 and 3.5 W for the wavelengths of 1064 and 1342 nm, respectively. The width of the hysteresis loop increased when the pump power increased. Moreover, the hysteresis loop accompanied with the variation of the pattern formation. A high-order transvers mode was easily observed at 1342 nm light, but a simple spot existed for 1064 nm light. Apparently, the role of gain competition is worthy to deeply explore.
Based on the birefringence of the laser crystal and cavity design, a simple method directly generate radially and azimuthally polarized laser beams with a c-cut Nd:GdVO4 in a three-element cavity. The experimental results reveal that the transformations of polarization are observed by tuning cavity length with hundreds of micrometer. The slope efficiency is maintained up to 36.7% and output power reaches up to 1.34 W with the pump power of 5 W. The degree of polarizations can be greater than 92.2% for both of azimuthally and radially polarized beams. By considering the extraction efficiency from pump energy with the condition of changing the cavity length for o-ray and e-ray, mechanism of polarization transformation in the laser is discussed.
The nonlinear dynamics of the Gaussian beam propagation in resonator was studied by constructing the iterative map of q-parameter. From the Greene's residue theorem, there are specific configurations sensitive to nonlinear effect existing in the geometrically stable region. By applying to Kerr-lens mode-locking (KLM) resonators, we found that multiple solution, period doubling, period tripling and period quadrupling can occur at the configurations with product of cavity G-parameters equal to 0, 1/2, 1/4 (or 3/4) and (2 +/- yields2)/4, respectively. Moreover, the systems will result in classical chaos if further increasing the nonlinear effect. We will also report appearance of unexpected transverse beam profiles and shrinkage of beam waist causes to lower laser threshold in an end-pumped Nd:YVO4 laser and chaotic behavior in the KLM laser around these critical resonator configurations.
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