Abstract: An ion-based atomic clock comprising an ion trap configured to trap a plurality of ions; and a micro-resonator-based frequency comb configured to directly drive a terahertz transition between metastable levels in the trapped plurality of ions. The micro-resonator-based frequency comb may be configured to directly drive a 24 terahertz transition in at least one Ba+ ion, a 8.4 terahertz transition in at least one Sr+ ion, or a 1.8 terahertz transition in at least one Ca+ ion. The micro-resonator-based frequency comb may be configured to provide output similar to a pulsed laser. The ion-based atomic clock may be free of a carrier-offset-stabilized frequency comb. The ion-based atomic clock may comprise a mini-vacuum ion trap assembly. Polarization of the micro-resonator-based frequency comb may be tuned to make the ion-based atomic clock be insensitive to laser light power fluctuations.