I recalculated the coatings properties, with the values of nH and nL to be 3.48 and 2.977. Note about each optimization is included here. Transmission plots are added in google spread sheet. I'll finish the calculation for E field in each layer soon.

Note about each optimized coating version: different versions were obtained from different cost functions, and different number of layers.

opt1

• 55 Layers
• T = 210 ppm
• TO noise and transmission is too sensitive to the change in nH and nL
• 1/4 cap of nH. I did not fix the cap thickness for other coatings. Since there is no reason to keep the thickness of the cap constant.
• TO noise and transmission of this one changes a lot with uncertainty in nH/nL

opt3

• 57 Laayers
• T = 150 ppm
• Transmission is still too sensitive to the change in nH and nL
• TO noise/ transmission is less susceptible to change in nH/nL.
• First layer is 0.1 lambda thick (~285 nm) I'm not sure if this will be a problem for a cap or not.

opt4

• 57 Layers
• T = 150 ppm
• TO noise and Transmission are less sensitive to nH and nL
• less amount of nL material, should be less sensitive to error in thickness control

opt5

• 59Layers
• T= 144 ppm
• TO noise and Transmission are less sensitive to nH and nL
• reflected phase is more sensitive compared to opt4
• use less nL material
• 0.1 lambda thick

Judging from TO noise level, Transmission and reflected phase, I think opt4 is the best choice for us. The structure consist of thick nH layers and thin nL layers. This is good for us in terms of thickness control.