Amplification of radiation in atomic vapor induced by a linearly polarized laser radiation

Abstract

Abstract:We present the results of spectroscopic and polarization studies of dilute rubidium vapor exposed to a single-frequency linearly polarized diode laser radiation in a spectral range of atomic D 2 line. We report the origin of a circularly polarized radiation on V-type transitions of 87 Rb F = 2 −→ F = 3 and 85 Rb F = 3 −→ F = 4, and amplification of this radiation in backward direction caused by a partial population inversion among magnetic sublevels of the ground and excited levels. This is confirmed experimentally by high directivity of backward radiation, absence in its spectrum of 85 Rb F = 2 −→ F = 1 (Λ-type) radiation, as well as by different nature of intensity dependences of backward and fluorescence radiations.

Evidence for degenerate mirrorless lasing in alkali metal vapor: forward beam magneto-optical experiment

“…The suppression of orthogonally polarized amplified radiation at B = 0 observed for I L > 100 mW/cm 2 (Fig. 5a) is in qualitative agreement with the experimental results obtained in [10]. This decline may be attributed to saturation effects, and will be investigated in more detail in future work.…”

“…3) Consistency of the laser-intensity range where magnetic resonance is observed ( Fig. 4) with the results of [10], where amplification due to partial population inversion on 85 Rb F g =3 → F e =4 and 87 Rb F g =2 → F e =3 transitions was directly recorded in the backward direction. 4) Outright absence of any orthogonally polarized output light for 85 Rb F g =2 → F e =1,2,3 and 87 Rb F g =1 → F e =0,1,2 (F e < F g ) transitions, independently of the B Z value (Figs.…”

“…3) Consistency of the laser-intensity range where magnetic resonance is observed (Fig. 4) with the results of [10], where amplification due to partial population inversion on 85 Rb F g =3 → F e =4 and 87 Rb F g =2 → F e =3 transitions was directly recorded in the backward direction.…”

“…In [10,11] it was demonstrated that interaction of linearly polarized light with a F e > F g cycling D 2 transition of alkali atoms (in particular, F g =3 → F e =4 of 85 Rb and FIG. 1.…”

“…In [10,11] it was demonstrated that interaction of linearly polarized light with a F e > F g cycling D 2 transition of alkali atoms (in particular, F g =3 → F e =4 of 85 Rb and The population inversion has strongly nonlinear dependence on the light intensity: above a threshold, the inversion increases reaching saturation followed by a decline. For B = 0 and linearly polarized pump light, there appears optical gain for polarization orthogonal to that of the pump light in the forward and backward directions [10]. Application of an external magnetic field should influence the redistribution of population due to Zeeman pumping in multiple absorption-emission cycles, thus affecting the onset of population inversion.…”