Random and modulated noise spectroscopy in a Lambda system

Lasers have inherent phase noise, which can be converted to amplitude noise after atom-light interaction. Previously, such PM-AM conversion has been extensively studied in a two-level system. The three-level Lambda system has attracted much attention in recent years due to its relevance to quantum memory, magnetometers and atomic clocks. We investigate PM-AM in this system with both random phase noise and modulated phase ``noise''. Atomic dynamics from both ground and excited states can be revealed from the output intensity noise spectrum. Responses of the system to noise show resonance behavior distinct from a two-level system. For the modulated noise case, adiabatic and nonadiabatic regimes were identified. In particular, using the intensity cross-correlation of the two optical fields as an observable leads to subnatural spectrum for the transition between the two ground states. We will present experimental and theoretical results.