# Simulation meeting 2022 Jan 13 15:00

Zoom2: https://zoom.us/j/6676627462

## Participants

Naoki Koyama, Marc Eisenmann, Haoyu Wang

## Agenda

### Updates from Projects

- Birefringence simulation
Theta map and alpha-minus map have high spatial frequency components (sharp features) which is a problem for simulation. F2F_talk

Theta is wrapped due to the tangent function. We are trying to unwrap theta, which can make the map smooth. unwrap_theta

- The offset (zero-order Zernike polynomial) of TWEs at two rotation angles may be different. Then the subtraction of two TWEs will have errors. This will contribute errors in calculating theta.
- How to ensure the offset of TWE stay the same after rotating the mirror in real TWE measurements?
- We are currently simulating round-trip loss in one arm cavity when birefringence is considered with the MZ model with fixed parameters (without maps).

- Birefringence characterization of Spare ETMY in NAOJ (Marc)
- The maximum value of Delta-n map is close between calculation and measurement.
- The calculation of theta map shows some sharp features while the measurement is quite smooth. There may be two reasons: 1) the denominator in calculating theta will be zero (if the subtraction of two TWE is zero), 2) theta is wrapped.

- GUI
- Koyama is writing his thesis and is going to graduate next month.