Stress-minimized laser-soldering for periodically poled nonlinear materials

The miniaturization of laser and quantum light sources is critical for the scalable deployment of classical and quantum communication systems, posing significant challenges for maintaining optical performance and mechanical integrity under environmental stress. We investigated Solderjet Bumping (SJB) as a bonding technology for integrating nonlinear optical crystals into compact laser and quantum devices, which offers long-term reliability and high environmental stability. The high temperatures and mechanical stresses involved during the soldering process can introduce stress-induced refractive index changes, potentially degrading optical performance in particular in nonlinear, periodically poled materials. To assess these effects, a FEM thermo-mechanical simulation is used to analyze stress and strain distributions generated by the SJB process. These results are subsequently exported and used to evaluate the influence on the refractive index, and on the nonlinear coefficient, which is critical for nonlinear processes such as Spontaneous Parametric Down-Conversion. PPKTP is the nonlinear medium for optimizing stress-induced packaging and characterization approach.