Optical Telecom-Band Clock using Neutral Titanium Atoms

We propose an optical clock based on narrow, spin-forbidden M1 and E2 transitions in lasercooled neutral titanium. These transitions exhibit much smaller black body radiation shifts than those in alkaline earth atoms, small quadratic Zeeman shifts, and have wavelengths in the S, C, and L-bands of fiber-optic telecommunication standards. For the most appealing and experimentally realizable clock transition at 1549nm, we have identified several convenient magic trapping wavelengths (781nm, 789nm, 1037nm). We calculate lifetimes; transition matrix elements; dynamic scalar, vector, and tensor polarizabilities; and black body radiation shifts of the clock transitions. We also calculate the line strengths and branching ratios of the transitions used for laser cooling. Finally, we identify challenges posed by magnetic dipole-dipole interactions and describe an approach to overcome them. We also briefly discuss technical details of building an ultracold Ti experiment. Direct access to a telecommunications-band atomic frequency standard will aid the deployment of optical clock networks and clock comparisons over long distances.