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Message ID: 154     Entry time: Mon Oct 31 12:51:13 2016
Author: Gabriele 
Type: General 
Category: Measurements 
Subject: Simulation of dilution factor and measured loss angles 

I made a COMSOL simulation of our wafer (75 mm with flats, 1 mm thick) with a 1 micron thick coating (Tantala), and computed the dilution factor (E_coating / E_total). The result is shown in the plot below:

The dilution factor is slighly mode dependent, around a value of 5.7e-3.

The Q we measured on the latest two annealed wafers are in the range of 5e6 - 10e6 for the good modes, meaning that the total loss angle (subtrate, surface and edge combined) is 1e-7 - 2e-7.

Assuming an undoped tantala coating with loss angle of 4e-4 (http://authors.library.caltech.edu/55765/2/1501.06371.pdf), the disk loss angle after coating will be 2.2e-6, a factor 5 to 10 higher than our uncoated and annealed wafers.

So we can use the wafers as they are for our measurements.


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