Prospects for frequency stabilization using collective effects of strontium atoms in an optical cavity

The stability of current state-of-the-art optical atomic clocks [1]-[5] is mostly limited by the frequency noise of the interrogation oscillator through the Dick effect. To achieve the heralded ultimate stability, future optical frequency standards will need to produce light sources with frequency stability at the 10
⁻¹⁷
fractional level or below at one second of integration time. Recently, a new frontier in cavity stabilized laser sources has pushed the fractional instability to the lower 10
⁻¹⁶
level at one second of integration time [6]-[8]. However, this instability is limited by thermal noise in the reference cavity elements and may be difficult to reduce further. These state-of-the-art reference cavities are technically challenging to construct and their stability is still at least an order of magnitude too large for lattice clocks to achieve their ultimate performance.