40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  Mariner elog  Not logged in ELOG logo
Entry  Fri Oct 1 12:01:24 2021, Paco, General, Design specs, TM Barrel coating emissivity stack_1.pdfstack_2.pdfstack_3.pdfinterpolated_n_k.pdf
    Reply  Fri Oct 1 13:24:40 2021, Aidan, General, Design specs, TM Barrel coating emissivity 
       Reply  Fri Oct 1 14:11:23 2021, Paco, General, Design specs, TM Barrel coating emissivity stack_1.pdfstack_2.pdfstack_3.pdf
Message ID: 35     Entry time: Fri Oct 1 13:24:40 2021     In reply to: 34     Reply to this: 36
Author: Aidan 
Type: General 
Category: Design specs 
Subject: TM Barrel coating emissivity 

I have to question whether this passes a sanity test. Surely in the case of Stack 2, the 10um thick Ta2O5 will absorb the majority of the incident radiation before it reaches the SiO2 layer beneath. It should at least be similar to just absorption in Ta2O5 with some Fresnel reflection from the AIr-Ta2O5 interface.

For example, at around 18um, K~2, so the amplitude attenuation factor in a 10um thick layer is 160,000x or a gain of 6E-6. So whatever is under the Ta2O5 layer should be irrelevant - there is negligible reflection.

Quote:

[Paco, Nina, Aidan]

We ran our stack emissivity calculation on different AR stacks to try and make a decision for the TM barrel coatings. This code has yet to be validated by cross checking against tmm as suggested by Chris. The proposed layer structures by Aidan and Nina are:

  1. *| Air || SiO2 x 800 nm || Ta2O5 x 5 um || Silicon |*
  2. *| Air || Ta2O5 x 10 um || Sio2 x 20 nm || Silicon |*
  3. *| Air || SiO2 x 100 nm || TiO2 x 1 um || Silicon |*

Attachments # 1-3 show the emissivity curves for these simple dielectric stacks. Attachment #4 shows the extinction coefficient data used for the three different materials. The next step is to validate these results with tmm, but so far it looks like TiO2 might be a good absorbing film option.

 

ELOG V3.1.3-