[Marc Shalika]

For all these measurements we set up HWP and QWP at the input beam to have as linear as possible light from our polarization camera.

Then, we placed the input polarizer aligned with this linear polarizer as in fig1. We got aximuth angle ~ - 0.05+/-0.05 deg and ellipticity ~ -0.23+/-0.02 deg.

After installing the output cross polarizer we got azimuth angle ~ -0.025+/-0.05 deg and ellipticity ~ 0.06 +/-0.02 deg as in fig 2.

• Extinction ratio

Before installing the output polarizer we installed each LC successively. We rotated the LC to find the minimum and maximum transmission. Then we swept the LC voltage from 0 to 25V and computed the extinction ratio from the transmitted power normalized by the input power.

For LC2, we found the max and min positions were matching well the principal axes but it was not the case for LC1...

• Fast axis direction

As pointed out by Shalika, our previous estimations of the LC fast axis where really dependent on the fitting parameters range. It could come from the fact that using several sine harmonics in our fit biased our estimation. We decided to use a different formula : P_trans = a * sin(2(theta-theta0))^2 with theta the rotation angle of the LC.

We swept the LC voltages at various rotation angles covering more than 90 deg as in fig4 for LC2. From the fit we could extract the fast axis direction of 12.18 deg. This is in really good agreement with our 'by hand' estimation of 11.43deg.

All the swept results are reported in fig5. It can be seen that we get the usual retardance varying from 17nm to 989 nm as a function of applied voltage for every rotation angle except when the LC fast axis is close to the input polarization direction. In that case the maximum retardance is only ~650 nm while smallest one is increased to ~ 60 nm.

We simulated a rotating LC inside cross polarizers. Input polarization and polarizers are assumed perfect but we added by hand a backgroud power of 22.12 nW as measured in cross polarizers without LC. The LC voltage response is coming from the fit of the value at 45deg rotation wrt input polarization direction and takes into account measured extinction ratio. Results are reported in fig6 and agree really well with our measurement (especially at low voltage). An offset of 0.75 deg creates a maximum retardance of 657nm!

For LC1, we repeated the same measurement and measured fast axis direction of 145.05 deg.

• Temperature effect

All these measurements are performed at 30 degC nominal value and we typically see variation of less than 0.1 degC.

We measured the retardance at 0V while changing the LC temperature and results are attached in fig 7.

For LC2 we measured a change of 9.81 nm / degC while for LC1 7.84 nm/degC.