Hichwa Award: Constructing LIGO: Building, calibrating, and testing my own Interferometer

During the Fall of 2018, I received the Hichwa Research award, and began my journey to simulating LIGO, the Laser Interferometer and Gravitational-Wave Observatory. LIGO is one of the largest scientific collaborations in the world, making measurements so fine they can detect ripples in spacetime billions of light years away. These ripples are mainly caused by two black holes colliding. The feats of engineering and physics involved are truly remarkable, and three leaders of the LIGO team were awarded the Nobel Prize in 2017 for their work. It was my goal in the Fall to construct a miniature version of LIGO, calibrated to the highest degree possible. To do this, I needed to make an interferometer.

An interferometer is a tool used by physicists to make very fine positional measurements using light. The laser system is comprised of a laser, a beam splitter, two mirrors, and a camera. The resulting pattern resembles a bullseye, with alternating light and dark circular bands surrounding a center. These bands are called “fringes,” and together a light and dark band make up one wavelength of light.

There were several challenges in building an interferometer, primarily in testing and fine-tuning the equipment, reducing the noise, and ultimately calibrating the interferometer. Due to the very fine measurements taking place, there is a lot of systemic noise in the system, ranging from the AC turning on all the way to people opening and closing doors down the hall from the lab, where the interferometer was built. With these challenges in mind, I managed to calibrate this interferometer to the best of my ability.

I calibrated my interferometer to approximately 2% of the laser’s actual wavelength. This means that there is approximately 2% error in my system. Once the interferometer was built and tested, I could continue to the next step in my Simulating LIGO project, completed as my senior capstone (see accompanying article).