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First Laser Switched on in LIGO Hanford Optics Lab

First Laser Switched on in LIGO Hanford Optics Lab

- Contributed by Fred Raab

Figure 1. Daniel Sigg With New Laser A compact 980-nm diode laser, turned on this May in the optics lab, is the first of many lasers to operate at the LIGO Hanford Observatory. The optics lab is where all the key mirrors for LIGO Hanford's interferometers will be mounted, balanced and finally cleaned. The lab will also support various R&D tasks. A fume hood will allow for work with any chemicals that may be involved in cleaning LIGO optics and a number of clean-air enclosures will allow researchers to work on optics in a dust-free environment. Optical tables and a "tool chest" of optical mounting hardware are now ready for a wide variety of tasks.

Figure 2. Doug Cook With Helium Neon Laser In Figure 1. at left, Observatory Scientist Daniel Sigg appears with his new laser. The laser is a solid-state diode device made from AlGaAs (aluminum-gallium-arsenide). Daniel is using the laser to develop a photon calibrator for LIGO interferometers. We need to be able to apply small, known forces to the LIGO mirrors to calibrate the sensitivity of the LIGO interferometers to mirror displacements. The photon calibrator derives its small force from the recoil momentum of photons--particles of light--that richocet off the mirror surfaces. The light from the 1 W laser will be strong enough to deflect a suspended LIGO mirror, which weighs 10.7 kg (about 24 pounds) by distances comparable to the radius of a proton. This may sound small, but this is well above the noise background in the interferometer, which should be approximately 0.001 proton radii.

At right in Figure 2., Optics Specialist Doug Cook is setting up a Helium Neon laser for testing. These old-fashioned gas lasers are cheap, convenient and reliable in applications like aligning optics or setting up small test interferometers. No optics lab should be without one! Doug is responsible for all optics and laser operations at LIGO Hanford and serves as our laser safety officer. Before the lab could begin operations, Doug needed to ensure that a laser safety program was in place. This includes arranging baseline eye exams for employees, and providing laser-safety partitions, warning lights and other laser potection devices, like the goggles worn by Doug and Daniel. Doug is also responsible for supervising clean-room practices that will provide a contaminant-free environment for our lasers and mirrors.