Always exciting to see our products used in unique ways to support research advancements! Our mid-infrared QCL and ICL lasers are often used for environmental sensing because gases absorb unique wavelengths in that region: https://lnkd.in/eMcG9gGh In this post, Gabriele Vajente shows how mid infrared light can also be absorbed in an optical material that looks clear with our eyes. LIGO Laboratory plans to use this property to create more stability in their extremely sensitive measurements of gravitational waves. How are Thorlabs products supporting your work? We love to share unique use cases with the community!
Scientist, Engineer and Educator | Leading R&D and Detector Improvements for gravitational-wave detection | Communicating science to the public
The LIGO Laboratory gravitational-wave detectors use many kinds of lasers, for many different applications. Our main laser, used to measure the teeny distance fluctuations created by gravitational waves, is one of the most stable near-infrared lasers in the world. But it’s not the only one. And recently we have explored a completely new kind of source (at least for us!): a Thorlabs Quantum Cascade Laser that emits light in the mid-infrared, with a wavelength of 4.65 micrometers. We needed a source capable of projecting a large beam, with a radius of about 5 cm, into our main mirrors. The goal is to mimic as close as possible the size and shape of the main laser beam. The mirrors absorb a very small fraction (less than a part per million) of the main laser, but since the power is very large, this results in some heating and deformation in the center of the mirrors. This deformation comes and goes every time the main laser goes on or off. The new laser we’re going to install soon will be on when the main laser is off, and the other way around, so that we can keep the center of our mirrors always hot, and avoid transients. That’s why we need to use a mid-infrared source: our mirrors are made of silica, and this material completely absorbs light at 4.65 microns. Therefore we can use only less than one watt of power at 4.65 micrometers to heat up our mirrors. In the past we used CO2 lasers that emit at 10.6 micrometers. But they are more difficult to use, require water cooling, and are less stable in intensity. Quantum Cascade Lasers are much more compact and easy to operate and set up. In the past few years they have reached high enough powers, up to a couple of watts, to be interesting for our application. After testing a few units in the LIGO R&D program (called ADTR, Advanced Detector Technology Research), we chose a commercial Thorlabs unit that meets all our specs in terms of beam shape, wavelength and stability. Additionally, using 4.65 microns light instead of 10.6 microns makes all optical components (lenses, polarizers, mirrors) much easier to procure, and photodetectors a lot more sensitive. This new system, called CHETA (Central HEater for Transient Attenuation) will be installed in 2026 at both the LIGO Livingston and LIGO Hanford detectors. Stay tuned for updates! #gravitationalwaves #interferometer #laser #optics #stem