8/3/2019 00907815
1/1
Tuesday/ 42
QTuEPPhase co ntrol reduction of four-wave mixing in induced
waveguidingscheme
D. Borrman-Arbiv,A. D. Wilson-Gordon and H. FriedmannDepartment
of Chemistry,Bar-llanUniversity,Ramat Gan 52900, IsraelTel:
-972-3-5318313,Fax: -972-3-53 1250, E-mail: [email protected]
inves tiga te the waveguiding i n d d n a weak probe propagating in
a medium oftwo-level atom s driven by a copropagating, intense,
strongly detuned pump. We show thatwhen the tra nsvene profile of
the pump exhibits solitonlike oscillations, similar oscillationscan
be induced in the transverse profile of the probe [l]. The pump
acts asa spatial soliton inthe sense that its transverse intensity
profile displays oscillating spatial behavior due lo theinterplay
of self-focusing and diffraction. When the probe waist size is
initially narrower thanthat of the pump, the probe adjusts its
width, &er a short propagation distance, to that of thepump. It
is found that the weak beam, which is created during propagation by
four-wavemixing, has a significant effcct on thc waveguiding of the
probe. Athough the waveguideeffect is essentially unlimited when
the effect of four-wave mixing is ignored, it becomesseverely
limited when the medium is optically thick and the effect of
four-wave mixingbewmes dominant [I]. However, it is possible to
reduce the effect of four-wave mixing byphase wntrol. By
controlling the relative phases of the pump and probe lasers,
bathabsorptive and dispersive propertiesmay bc manipulatcd. With a
proper mechanism of phasecontrol and appropriate phase correction
scheme, the w d our-wave mixing wave can beforced to remain mall
during most of the propagation distance through the medium, so
thatthe waveguiding effect can be clearly discerned. This work
suggests that the imporlance offour-wave mixing in modifying
induced waveguiding should be considered in otherwaveguiding
schemes. The potential of phase wntrol in manipulating the
properlies ofpropagating laser ight in a sophisticated way
isemphasized.[I1 D. Boaman, A. D. ilson-Gordon, nd H. F r i e d ,
Phys. Rev. A (in press).
QTuE3Effect of propagationon pulsed four-wave mixing
P. Weisman, A. D. ilson-Gordon and H. FriedmannDepaNnent of
Chemistry, Bar-llanUniversity, Ramat Gan 52900,IsraelTel:
-972-3-5318313,Fax: -972-3-5351250, E-mail:
go&[email protected]
It is well-known that the steady-state four-wave mixing (FWM)
spectrum, obtained whena two-level atomic system interacts with a
coherent pump of arbitrary intensity and a weilkprobe, is
symmetrical and consists of three peaks: a central peak and two
Rabi sidcbands.Previously, we showed [I], for tempnrally
nonoverlapping pulses, that the specmm bewmesextremely asymmetrical
and that only the Rabi sideband near the resonance
frequencysurvives, in the case where the probe precedes the pump.
For the oppnsitc case, where thepump precedes the probe, no FWM
spec is obtained at all. It should be noted that theseresults hold
hue provided the pump and probe pulses are much shorter than the
transverserelaxation time T, and the pum p-probe time delay AI0
(Ato < 0 when the pmbe precedes thepump). We have also shown [l]
that T, can be determined from the slope of the semilog plotof the
FWM intensity, near the resonance sidehand, versus thc pump-probe
time delay Ai o(for the case B l o c 0).We now study [2] the effect
of propagation on he FWM spec! for modera te ly longoptical
pathlength To this end, we solve the Milxwcll-Bloch equations
numerically far anarbitrarily intense pump pulse and a w d robe.
Previous studies of the effect of propagationon FWM in a two-level
atomic medium referred to degeneratc FWM and were limited toweak
pump pulses.We will show that as propagation proceeds, the semilog
plot of the FW Mintensity versus Ala (for the ~ a ~ eIO 0) which is
initially linear, begins to deviate fmmlinearity and may even
change the sign of its slope for a range of values of AIO This
occursfor both weak and stmng pumps and is due to the behaviour of
the overlap of the pumpenvelope with the wherent response of the
medium to the probe. both of which are modifiedon propagation. In
addition, the FW M signal which is negligible for Afo > 0
compared to AI0< 0, in the absence of propagation, becomes
comparable to it when propagation is taken intoaccaunt.[I] .
D.Wilson-GordonandH. Fr iedm m, I. Phys. Chem. A 102,9651
(1998).[Z] . Weisman, A. D. Wilson-Gordon, and H. Fried Phys. Rev.
A (in press).
0-7803-6318-31001510 . ~ 0 0 0EEE
