Stimulated Raman gain in a Λ-type atomic system with doubly excited transitions

Abstract

Measurements of stimulated Raman gain in rubidium vapor are made and compared with a detailed model. Amplification of a weak probe laser is observed in a ⌳-type three-level system that is driven by a strong cw coupling laser. The intensity of the coupling laser is sufficiently strong that it both optically pumps the atomic levels, causing a population inversion in the ground-state hyperfine levels, and drives the stimulated Raman process producing gain. A theory that models all aspects of the gain mechanism is presented. The model includes all interactions between the external fields and the atomic transitions, including those processes that involve multiple fields interacting with the same transition. Numerical calculations are compared with gain measurements made at several coupling laser intensities and detunings from the D1 line in 85 Rb.

Narrow band amplification of light carrying orbital angular momentum

“…In the present work we use ground-state coherence between Zeeman sublevels of the cesium hyperfine ground state 6S 1/2 (F = 3), induced by nearly resonant coupling and signal beams to obtain cw gain on the signal beam. Similar gain mechanism has been investigated before by many authors and modeled using a three-level Λ scheme driven by two coherent fields in presence of optical pumping induced by the strong coupling beam, which in this case needs to interact with both transitions of the Λ system [15,16]. Previous related works have also investigated gain in three-level Λ scheme in the context of laser without inversion (LW I), where an extra incoherent [17] or coherent [18] pumping beam is used.…”

Atomic filter based on stimulated Raman transition at the rubidium D1 line

“…As shown in Fig. 5, the bandwidths of the transmission spectra based on the stimulated Raman transition remain <22 MHz when the signal light power is 26 μW [17]. The transmission spectra show a maximal Raman gain factor of 85 shown in Fig.…”

“…Certain light amplification schemes, such as light amplification without inversion in any standard state basis, light amplification by stimulated Raman scattering, and light amplification from population inversion in the dressed states, have been analyzed and realized experimentally [15][16][17]. In particular, Zhu [16] systematically analyzed light amplification mechanisms in a coherently coupled atomic system.…”

Steady-state signatures of radiation trapping by cold multilevel atoms

“…The pump beam is obtained from a master laser which is then amplified by two stages of saturated slave lasers; hence, by tuning the frequency of the master laser using a double-pass acousto-optical modulator, we can scan the detuning δ P of the pump with respect to the F = 3 → F = 2 transition by more than 16Γ without altering its intensity by more than 0.1%. Note that when the pump is detuned from the F = 3 → F = 2 resonance, and if the F = 3 state is more populated than F = 2, Raman gain (F = 3 → F = 2 → F = 2) can be obtained in this system [15,16,[31][32][33]]. An additional repumper on the F = 2 → F = 3 transition controls the population balance between the hyperfine ground states of 85 Rb in the steady state regime.…”