Research Towards Future Gravitational-Wave Observatories: Lasers, Optics, Materials, Devices, and Simulations

This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. Beginning with the September 2015 discovery of gravitational waves from the inspiral of two black holes, NSF's Laser Interferometric Gravitational-Wave Observatory (LIGO), in conjunction with Virgo, have carried out observational campaigns for gravitational waves, with more than 90 mergers of compact objects (black holes and/or neutron stars) reported from three observing runs. A fourth observing run, with significant improvements in sensitivity and performance will begin in Spring 2023. This A+ upgrade of the detectors includes six low-loss Faraday isolators designed and manufactured at the University of Florida. Ongoing research aims at contributing to further improvements as well as to third-generation gravitational-wave detectors. This work will positively influence the national and international scientific infrastructure through the direct participation of the University of Florida LIGO group in research and operations at the LIGO Observatories. The research will go beyond gravitational-wave science. High-power optical isolators developed in this project have commercial applications to the laser and optics industries. A single-frequency 2.1 μm laser, tunable over GHz of frequency, can affect many areas of precision science. The Florida group also contributes service activities to the LIGO-Virgo-KAGRA collaborations by serving on a variety of standing committees. The Florida group also gives students and postdoctoral scientists the opportunity to develop scientific skills from a diverse set of disciplines spanning lasers and optics, electronics and feedback control systems, vacuum and cryogenics, and large-scale detector commissioning and operation. In addition, the group places high value on the education of undergraduate students and each year has involved undergraduates in research. Advanced LIGO was designed for a tenfold sensitivity improvement and much better low-frequency response than initial LIGO. With the introduction of squeezing and the A+ upgrade, the sensitivity will be increased further. These gains require improved performance in all aspects of the detector, including the Input Optics, a responsibility of the Florida LIGO group for many years. Work will address high-power optical isolation, improved modulation of laser beams, and improved simulations of the suspensions used for in the input optics and in the core interferometer. It also addresses basic research needed for next generation detectors aimed at increased science reach. This longer-ranged research includes studies of modulators and isolators at longer wavelengths than the 1064 nm wavelength currently used, completion of analysis of impurities in silicon, a nearly ideal material for the test masses of cryogenic detectors, and the characterization of a single-frequency non-planar ring oscillator laser operating at 2.1 μm wavelength. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.