Recently we have some worry about squeezing measurement about losses(entry 1532). Although we have the main worry about OPO intra-cavity loss, we also want to replace the normal lens we are using with the super-polished lens from CVI company.

I checked the simulation of Eleonora Polini(entry 1311), there are some discrepancies.

• the database Eleonora was using is out of date because she is using thorlabs database while we are buying from CVI.
• the distance from PBS to waist is not consistent with my calculation. I also asked Aritomi-san to check this distance. He has the same result as me.

According to these difference, I did the calculation again. The distance(from bench to waist close to 2-inch mirror) is estimated as attached in Figure 1. This is only an approximation. But since it is a very collimated beam, I think it is fine. In this approximation, the black number is provided by Yuefan and Eleonora (entry 1133) while the purple number is calculated according to these number. The distance is estimated by the holes on the bench (2.5cm between two holes). The distance on the bench is summarized as follows:

• Injection: count from PBS(0cm), the first steering mirror(17.5cm), Faraday isolator(32.5cm), the second steering mirror(47.5cm), the third steering mirror(57.5cm), the fourth steering mirror(77.5cm) then goes to the edge of the bench. We need to pay attention to that squeezing reflection will be between 67.5cm to 72.5cm.
• Reflection: first we consider the distance from the waist around the 2-inch mirror to bench edge, it is 427.3cm. count from bench edge(427.3+0cm), the first steering mirror(427.3+5cm), the second steering mirror(427.3+22.5cm), the third steering mirror(427.3+35cm), then goes into homodyne and finally into alignment mode cleaner(427.3+81.25cm).

With this distance information and new database, I simulated again the telescope. I tried to choose the result based on the already bought lens from CVI.

The result is attached in Figure 2 and 3. In this case, we are using PLCX-25.4-149.9-UV and PLCC-25.4-515.1-UV for injection. And we are using PLCX-25.4-124.9-UV and PLCC-25.4-51.5-UV for reflection. The lens in the red color we have in the lab.