Material Qualification RGA Test Results: High Quantum Efficiency InGaAs Photodiode

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Abstract:: Custom high quantum efficiency InGaAs photodiodes were purchased from Laser Components Inc. (part number is IGHQEX3000). This document reports on RGA test results for qualifying this part and it's cleaning/processing for use in the LIGO UHV system.

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Notes and Changes:: 5/12/2016 Update (shoudl be incorporated into -v2):
A first attempt at qualifying these high quantum efficiency photodiodes (IGHQEX3000) was presented in this document E1600086-v1. A proposal ( L1600055) was made to the VRB to forgo baking these PDs. The VRB insisted on an air bake at 75C and verification that the peak at 64 AMU was no longer in the spectrum ( L1600056).
A second pair of PDs was air baked at 75C and scanned in ICS8116. The ICS8116 scan is about the same as shown in E1600086-v1, which was rejected by the VRB. The background scan (RGA only) indicates that the RGA head is contaminated. Consequently, the PDs were placed into a container with N2 (to keep moisture off), the RGA head was baked at 300C for 48 hrs by itself. The head was confirmed to have a clean scan. Then the PD pair was put into the vacuum chamber and scanned again (without a vacuum bake). This scan:
https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Bake-8122
is "clean", i.e. no hydrocarbon signature. Consequently, this load passes AND future high QE PDs can be cleaned (per the minimal procedure in E1600086) and then air baked at 75C for 48 hrs without requiring an RGA scan (per L1600056).

LIGO Document E1600086-v1