## 4 Discussion  
The results demonstrate promising performance with high efficiency, suggesting that our design is competitive with the state of the art. The achieved black-box efficiency is significantly higher than that of other systems, due, in part, to the direct-diode pumping approach used in this design. Notably, devices utilizing fiber amplification before pumping the nonlinear crystal have reported lower efficiencies, which we believe is because our approach avoids the additional losses associated with amplification stages. Additionally, the cavity enhancement factor of our system, driven by the high-quality optical coatings, is another contributor to the improved efficiency. For example, the Finesse of our cavity (~200) and the corresponding pump enhancement factor (~30) give it a distinct advantage over other systems like that of [PERSON] et al., who reported a Finesse of 65 and a pump enhancement factor of ~10.  
Despite these successes, there are areas where improvements can be made. One area for potential improvement lies in the beam overlap. While the signal overlap with the current pump beam has been optimized, the 1064 nm pump itself is underfocused. Increasing the focus factor to ~2 for the pump would lead to another similar jump in efficiency. However, implementing this improvement would likely require a redesign of the cavity and a re-evaluation of the focusing setup. Future experiments will need to explore the feasibility of decreasing the pump beam size or modifying the signal beam size to enhance overlap, although this may lead to some trade-offs in intensity.  
Our theoretical analysis also indicates that there is room for further improvement. For example, increasing the pump power could potentially drive the circulating power even higher, improving the efficiency further. However, such changes would also bring new challenges, particularly with thermal lensing effects, which may compromise cavity stability as the pump and signal powers increase. Thermal effects, including those caused by multi-watt signal and pump powers, will need to be better understood and managed. While the current model approximates thermal lensing effects, a more comprehensive approach is necessary for future work.  
In terms of device performance, we have identified areas where the design can be enhanced, such as improving the optical coatings and considering the nonlinear losses that become more pronounced with higher efficiency. These losses are currently not significant but could have a greater impact if the efficiency is pushed further. Nonlinear losses in the cavity, especially at higher powers, may also impact the overall performance, similar to previous observations in nonlinear processes like SHG. Future investigations will focus on understanding these effects more thoroughly.  
Finally, in terms of application, the design shows great promise for portable mid-IR detectors. The compactness of our system, with a cavity length of less than 8 cm, along with the potential for a further reduction of this size, makes it suitable for remote sensing and gas detection. We have shown that it is possible to maintain high performance with shorter PPLN lengths, and ongoing efforts will aim to make the system even more portable. Moreover, we are exploring the use of this system in high-throughput secure networks, including the demonstration of mid-IR free-space optical links for atmospheric mitigation purposes.