Optical atomic clocks are some of Earth's most precise and accurate instruments. Like how a wristwatch uses an oscillating electronic signal ("the oscillator") and a quartz crystal ("the reference") to keep time, an optical atomic clock uses a laser referenced to optical transitions in atoms. Many applications of these instruments, such as space-based gravitational wave detection, tests of relativity, deep space navigation, and geodesy, require compact and portable optical atomic clocks. However, creating compact clocks for field use remains challenging owing to the size and complexity of the equipment used to control the motion and temperature of clock atoms.

This talk will discuss three novel architectures for compact and portable optical atomic clocks and the work done toward implementing them. Two of the clock designs use two-photon transitions, which eliminate the need for confinement of the atoms and sub-Doppler cooling: one system is based on neutral rubidium (Rb) atoms and the other on neutral calcium (Ca) atoms. The third system uses samarium ions (Sm2+) rigidly fixed with a crystal. The talk will review each system's design, detail the experiments used to search for clock transition frequencies, and present the results of these experiments along with other key measurements.