Chip-scale atomic clock with two thermal zones

A chip-scale atomic clock comprises a physics package and a laser die (110) located in a first thermal zone of the physics package. A quarter wave plate (120) is mounted in the physics package and is in optical communication with the laser die. A vapor cell (130) is mounted in the physics package and is in optical communication with the quarter wave plate. The vapor cell is located in a second thermal zone that is independent from the first thermal zone. An optical detector (140) is mounted in the physics package and is in optical communication with the vapor cell. The first thermal zone (118) provides a first operation temperature at a first stability point associated with the laser die, and the second thermal zone (141) provides a second operation temperature at a second stability point associated with the vapor cell.