Coherent population trapping

EIT is based on the phenomenon of coherent population trapping [Harris 1997 Scully 1997 Liu 2001], in which the application of two laser fields to a three-level A system creates the so-called "dark state", which is stable against absorption of both fields. Dark states are also found in several other... 

The equation of motion (115) allows us to analyze conditions for population trapping in the driven A system. In the steady state (p = 0) with p / 1 and Ac = 0 the population in the upper state p33 = 0. Thus the state 3) is not populated even though it is continuously driven by the laser. In this case the population is entirely trapped in the antisymmetric superposition of the ground states. This is the CPT effect. However, for p 1 and Ac = 0, the antisymmetric state decouples from the interactions, and then the steady-state population p33 is different from zero [46]. This shows that coherent population trapping is possible... 

E. Arimondo, Coherent population trapping in laser spectroscopy. Progr. Opt. 35. p. 257 354,(1996). 

In this section we present a brief historical account of LICS without going into too many details, as our main concern is aspects of quantum interferences. LICS was initially suggested by Heller and Popov [4] and by Armstrong et al. [27], who termed the effect "pseudo-autoionization." Early theoretical investigations on LICS focused on coherent population trapping [28, 29], multichannel effects [30-33], and Raman-type transitions [2, 34 0]. 

The topics that mainly concern us in this review have to do with the connections between various coherent optical experiments and LICS. In the next section we discuss the relation between LICS and EIT, examples of which include experiments done in Rb [83,84] and Kr [85]. We then extend the discussion to EIT with structured continua [86, 87]. We proceed by reviewing the use of LICS in the control of population transfer processes [88] the control of PD [89] the production of photo-electrons [90-92] and as a means of steering population transfer processes [93]. We also discuss the connection between LICS and ultrafast methodologies [94] generalized STIRAP techniques [95-97] and coherent population trapping [69,93, 98-101]. 

Phase control of two-channel photo-ionization rates and coherent population trapping induced by four laser fields operating on an atomic system initially in its ground state 1), which proceeds via a pair of intermediate bound states, 2) and 3), to a manifold of structureless continua, has also... 

G.-X. Li, J.-S. Peng, Coherent population trapping in multilevel laser-induced continuum structure system. Opt. Commun. 138 (1997) 59. 

Champenois, C. Hagel, G. Houssin, M. Knoop, M. Zumsteg, C. Vedel, F. Terahertz frequency standard based on three-photons coherent population trapping, Phys. Rev. Lett. 2007, 99, 013001 (4). 

A. Aspect, E. Arimondo, R. Kaiser, N. Vansteenkiste, C. Cohen-Tannoudji, Laser cooling below the one-photon recoil energy by velocity-selective coherent population trapping. J. Opt. Soc. Am. B 6, 2112 (1989)... 

G S. Agarwal, and K. T. Kapale. Subwavelength atom localization via coherent population trapping. Journal of Physics B Atomic Molecular and Optical Physics 2006 Aug 14 ... 

E.Arimondo. Coherent Population Trapping in Laser Spectroscopy. Elsevier Science 1996 35 257-354... 

We adopt here the realistic parameters from a recent experiment on coherent population trapping (CPT) in diamond N-V color centers [40], in particular, using = 315GHz and... 

Santori C, Fattal D, Spillane SM et al. Coherent population trapping in diamond N-V centers at zero magnetic field. Optics Express 2006 Aug 21 14(17) 7986-7993. 

O. Schmidt, R. Wynands, Z. Hussein, D. Meschede Steep dispersion and gToup velocity below c/3000 in coherent population trapping. Phys. Rev. A 53, R27 (1996)... 

E. Arimondo Coherent population trapping in laser spectroscopy. In Progress in Optics XXXV, ed. by E. Wolf (Elsevier, Amsterdam 1996) p.259... 

One more trend in laser control is based on the use of the property of coherence of the laser light. To effect coherent laser control, it is necessary that not only the light, but also the atom (or molecule) should be in a coherent state during the interaction. For atoms in a beam or in a low-pressure gas, the phase relaxation time of their wave functions depends on spontaneous decay or on collisions and can be comparatively long (from 10 to 10 s). It was for precisely this reason that the main experiments on coherent interaction were conducted with atoms. These experiments led in the final analysis to the discovery of new effects, such as coherent population trapping (Arimondo 1996), electromagnetically induced transparency (Harris 1997), and the slow-light effect (Hau et al. 1999 Kash et al. 1999). 

A still more interesting effect, referred to as coherent population trapping, arises in three-level systems, when an atom is prepared in a state that is a superposition of two states, 1 and 2 (Fig. 4.7(a)) ... 

Fig. 4.7 Coherent population-trapping effect with optically oriented atoms (a) coherent population trapping between two levels (1 and 2) and an excited state 3 in a laser field with two frequencies (wi and LJ2), laser fields (b) steady-state excited-state population pss for a A-system as a function of the Raman detrming Sr, with the typical central dip associated with the coherent population-trapping phenomenon. (Adapted from Arimondo 1996.)...

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