Study of fundamental wave depletion in intracavity second harmonic generation

Abstract

In this paper, a novel approach to modelling intracavity second harmonic generation (SHG) in periodically poled MgO-doped lithium niobate (PPLN) is presented and verified against experimental results. This approach involves combining the coupled nonlinear wave equations with a rate equation model for a diode-pumped solid-state Nd:YVO4 laser, taking into account both the depletion of the fundamental wave due to the energy conversion from the fundamental wave to the SHG wave and the reduction of the fundamental wave within a laser cavity due to the loss as a result of the SHG nonlinear process. It was shown that the theoretical simulation matched the experimental results well, while also providing physical insight into the importance of the fundamental wave depletion in the intracavity SHG nonlinear processes. The resulting model is computationally simple and has the potential to generalize to the other nonlinear processes such as three-wave mixing and optical parametric oscillation.

A Systematic Study of PPLN Length Dependence in Intracavity SHG

“…Despite these drawbacks, the overall logarithmic trend and the relatively good agreement of the theoretical prediction with the experimental trend shows that these effects are not major effects that must be considered with our laser. While the model would most certainly be improved by adding modeling for multiple modes and Gaussian propagation, this work and the work in [32] show that reasonably close results can be obtained for the maximum SHG power using a simplified single mode model that requires significantly less computational power. Additionally, the lack of wavelength selection device in our laser can be attributed to our target application, which is low-cost, compact, watt-level lasers that can be manufactured easily.…”

“…This figure presents the simulated results for maximum SHG power (y-axis) versus MgO:PPLN length (x-axis) for an 808 nm pump power of 2, 3, 4 and 5 W (solid lines). The simulation was developed in-house by our research group and has been reported in a previous publication [32]. While the model is described in full detail in the cited publication, we will briefly summarize the model here.…”

“…The leaking fundamental power can be estimated in the simulation by taking the calculated steady state intracavity power and multiplying by the transmission of the OC mirror. For a list of the typical loss values and other simulation parameters used in the intracavity model, please refer to [32]. The circulating fundamental power inside the cavity was measured experimentally by performing the reverse operating, where the measured leaking power was used alongside the transmission of the OC to estimate the intracavity power.…”

“…The theoretical results were found to be in good agreement with the experimental results. For a more in-depth discussion on the theoretical model, refer to [32].…”

A systematic study of PPLN length dependence in intracavity SHG

“…For a list of the typical loss values and other simulation parameters used in the intracavity model, please refer to Ref. 32 . The circulating fundamental power inside the cavity was measured experimentally by performing the reverse operating, where the measured leaking power was used alongside the transmission of the OC to estimate the intracavity power.…”