The end-resonance clock uses strong hyperfine end transition to stabilize the frequency of the local oscillator.
Comparing to the conventional 0-0 atomic clock, end resonance has very small spin-exchange broadening effect. The
spin-exchange rate is proportional to the number density of the alkali-metal atoms. By using the end resonance, we are
able to use very high dense vapor to obtain a much better signal to noise ratio. On the other hand, the end resonance
suffers from the first-order magnetic field dependence. This problem, however, can be solved by simultaneously using a
Zeeman end resonance to stabilize the magnetic field. Here, we report the most recent result of the end-resonance clock.
In addition, we report a whole new technique, push-pull laser-atomic oscillator, which can be thought as all-photonic
clock. This new clock requires no local oscillator. It acts like a photonic version of maser, which spontaneously
generates modulated laser light and modulated voltage signals. The modulation serves as the clock signal, which is
automatically locked to the ground-state hyperfine frequency of alkali-metal atoms.