Characterization of Optics for LiGO

Photonics Media contacted GariLynn Billingsley, senior optical engineer and Advanced LIGO COC group lead at Caltech, and she generously provided access to images documenting the preparation of “test masses” (mirrors) prior to their installation at the Hanford, Wash., and Livingston, La., observatories.

Billingsley explained that there are 19 large optics in each interferometer, and with enough mirrors for three interferometers, she and her team have completed these processes 57 times.

The photographs in this series include: installation of a test mass mirror into a mount for measurement (Sequence 1); alignment of the installed mirror in front of an interferometer (Sequence 2); and removal of a cleaning polymer film and inspection for contamination with a green LED (Sequence 3). Additional measurements not photographed include reflection, transmission, absorption, and scatter scans.

Billingsley, who is shown in many of the images performing measurement and other tasks, described the cleaning and inspection as “pretty fast, [taking] about one day.” She explained, “Mounting or dismounting an optic takes about 45 minutes nowadays, but the first time we moved one it took three hours! The figure measurement takes about two weeks. All combined, it takes about one month to fully characterize an optic.”

Sequence 1

Courtesy of Caltech.

Sequence 2

Courtesy of Caltech.

Sequence 3

Courtesy of Caltech.