The scientific objective of this project is to build time-domain models for the Input Optics system of the Advanced LIGO (AdvLIGO) detector using the LIGO end-to-end (e2e) simulation package. With these models, various numerical tests will be performed to better understand the detector's performance and assess the AdvLIGO design. The LIGO detectors are Michelson interferometers designed to detect extremely small strain of space-time. To increase the optical path, the arms are configured as optical cavities. The input optics system is placed between the laser source and the interferometer, and its main function is to reduce the spatial jitter of the incoming laser beam and mode match the output beam to the interferometer. These activities are complementary to the tasks of various LIGO Scientific Collaboration (LSC) working groups, each of which focuses on designing a certain AdvLIGO subsystem. The role of this project is to combine those subsystem models developed by other groups, and study the performance of the integrated system. To this end, (1) an e2e model of the integrated system is built, (2) the built model is validated through comparison with measurement and (3) the system's performance is assessed under various realistic conditions. This project will provide valuable opportunities for undergraduate students to participate in the project and thus to learn not only related physics but also basic collaborative skills as a member of the project team such as responsibility and time management.
The objective of this research was to support a scientific research project known as LIGO (Laser Interferometer for Gravitational-wave Observatory). LIGO’s goal is to detect ripples of space-time known as gravitational waves. Gravitational waves were predicted by Albert Einstein as a consequence of his theory of general relativity. Theoretically predicted gravitational wave detectable with a ground-base detector like LIGO is extremely small; in the unit of strain (defined by stretch over the total length) it is on the order of 10-21 or smaller. To detect such a small signal, an extremely sophisticated optical interferometer has been designed. Naturally, the technical challenge is how to reduce the noise floor of the instrument. As of September 2011, an upgraded version of interferometer called Advanced LIGO detector is being assembled. Our group’s primary focus was to investigate the performance of the Advanced LIGO detector via numerical analysis of the instrument. We built several models to simulate the detector, and using the simulation models, analyzed the expected performance of the detector. Our findings include the noise level associated with the ground motion, the noise due to heat caused by the laser light passing through various optical components of the detector, and possible mechanisms that increase the noise. As a primarily undergraduate institution, involvement of undergraduate physics major students in the research was also an important element of the project. During the four project years, we involved six undergraduate students. They certainly deepened their understanding of the physics underlying the LIGO detector and its performance. Of these two students, two graduated from our university with an undergraduate physics degree, and continued to physics graduate programs of other universities. These undergraduate student researchers inspired other students as well. This led to a culture of undergraduate research in our department, which is evidenced by several facts including (a) most students enrolled in our department are now involved in research in one way or another by their junior years; (b) our student organization (our local chapter of the Society of Physics Students) organized a undergraduate research conference on our campus, and (c) our students made 45 research presentations at regional and national scientific meetings in the 2010 academic year alone.
