Fig. 1
(a) Schematic of the experimental setup utilized for generating IDS. ECDL, external-cavity diode laser; OI, optical isolator; HWP, half-wave plate; MOPA, master-oscillator power amplifier; CL, cylindrical lens; PBS, polarizing beam splitter; FC, fiber collimator; L, lens; BB, beam blocker; BPD, balanced photodetector; SA, spectrum analyzer. (b) Energy level diagram of the double-Λ system associated with the D1 transition line of rubidium, illustrating the experimental generation and detection of the squeezed state of light via FWM. νHF, hyperfine splitting; Δ, one-photon detuning; δ, two-photon detuning; DM, D-shaped mirror. The FWM process occurs within a heated Rb vapor cell where two beams, the pump and probe-seed, intersect at a small cross-angle. After polarization and spatial filtering to eliminate the pump beam, the resulting FWM twin beams are detected by the BPD. The output from the BPD is subsequently analyzed by a radio frequency SA.
