Firstly, Puttiwat investigated approximation of the Shack-Hartmann wavefront sensor (SHWFS) measurement in simulation. He compared the traditional method against the intensity-weighted mean gradiant method. Unlike the first method, the second uses only the wavefront's information at the pupil plane without calculating the focal plane of the wavefront sensor. The new method was found to use as low as 30% of the computational time and memory usage of the traditional method. The approximation error is neglible for Rytov parameter (scintillation) less than 0.3. Higher Rytov parameter were not included in the study. Lastly, he simulated that the measurement noise of the SHWFS does not vary with scintillation. This  shows that the optical propagation can be approximated using a geometrical approximation in some conditions. Potential future research includes validating the approximation between optical plane at altitude and ground.

Lastly,  Puttiwat explored the pupil distortion effect seen by solar multi-conjugated adaptive optics system, leading to dynamic misregistration and distortion of the calibration between the WFS and deformable mirror (DM). He hypothesised dynamic misregistration parameters, namely, DM-induced Rytov parameter and RMS apparent actuator shift to DM's pitch. He then derived analytical equations explaing the behaviours and verified against his simulation. AO control loop will have severely reduced performance when the DM-induced Rytov parameter larger than 0.1 or RMS actuator shift larger than 10%. Mitigation method is left for future study.

Puttiwat says:

"It is my pleasure and honour to join the CfAI for the last four years of my life. I had been received warmly by the whole group; professor, staff, and student alike. Scientific discussions and collaborations are just down the hallway. We also had lots of group social activities where we break the ice and form lifelong bonds."