Observation of intracavity electromagnetically
induced transparency in Cs vapor coupled
with a standing-wave cavity
Haitao Zhou (周海涛)*, Shaona Che (车少娜), Pengcheng Zuo (左鹏程),
Yuhong Han (韩宇宏), and Dan Wang (王 丹)
College of Physics and Electronics Engineering, Shanxi University, Taiyuan 030006, China
*Corresponding author: zht007@sxu.edu.cn
Received February 16, 2017; accepted April 21, 2017; posted online May 12, 2017
The cavity transmission spectrum is experimentally investigated in Λ-type three-level atoms coupled to a stand-
ing-wave cavity system. It is shown that the dark-state polariton peak is not generated at resonance but rather at
off-resonance. The theoretical analysis reveals that the absence of an on-resonance dark-state polariton peak is
mainly caused by the strong absorption of the intracavity medium to the probe cavity mode counterpropagating
with the coupling field due to the Doppler shift in the hot atoms. Moreover, the optimal frequency position of the
cavity mode for an efficient dark-state polariton peak is also demonstrated.
OCIS codes: 140.4780, 020.1670, 270.0270, 190.0190.
doi: 10.3788/COL201715.081401.
Cavity quantum electrodynamics (QED)
[1–3]
is mainly re-
searching the interaction process with a coherent atomic
medium placed inside an optical resonant cavity, and has
been of great interest in recent years. A well-known cavity-
QED effect is the vacuum Rabi splitting or normal-mode
splitting phenomenon that is under the strong coupling
condition, where the cavity transmission spectrum
exhibits a double-splitting-peaked profile when two-level
atoms are coupled into a single cavity mode
[4–7]
. Based on
the above, when strong coherent light is injected into the
intercavity medium to form a Λ-type three-level struc-
ture in which the electromagnetically induced transpar-
ency (EIT) is prepared
[8,9]
, the cavity transmission
spectrum produces an additional narrow central peak
under the condition of the two-photon r esonance, that
is the intercavity EIT (i.e., dark-state polariton)
[10]
.
Possible applications of intracavity EIT includ e long-
lived storage of quantum information
[11]
, preparation of
squeezed or entangled states
[12,13]
, a nd high-resolution
spectroscopy
[14,15]
. The three-peak spectrum of a three-
level EIT atom-cavity system has been demo nstrated
in cold atoms
[16,17]
,singleatoms
[18]
, hot atomic
vapor
[19,20]
, and ion Coulomb crystals
[21,22]
. The EIT effect
was also achieved with a terahertz f requency in a wave-
guide cavity and meta-atoms
[23–25]
. Recently, the four-
wave mixing effect
[26,27]
based on the atom-cavity system
has also been researched
[28–31]
. However, the spectrum
property of the hot three-level atom standing-wave cav-
ity (SC) system has not been reported yet.
As the resonant probe mode is copropagating with the
coupling field for the comp osite system with hot Λ-type
three-level atoms inside a ring cavity (RC), which is Dop-
pler free for the intracavity moving atoms to the probe
mode and coupling frequency, the intracavity EIT is
achieved at the center of atomic resonance when the
two-photon resonance is satisfied
[20]
. In this Letter, we ex-
perimentally demonstrate the cavity transmission spec-
trum in a hot Cs vapor coupled to a near-confocal
standing-wave cavity (SC) by controlling the frequency
detunings of the coupling field and the cavity-mode field.
Quite different from the situation of an optical RC
[19]
, how-
ever, it is shown that the dark-state polariton peak is cre-
ated not at the center of atomic resonance but rather at
off-resonance. Theoretically, the Doppler-shift effect due
to the hot atoms and the coherent pump effect of the cou-
pling fields
[9,18]
can give a qualit ative interpretation. Fur-
thermore, the multipeak profiles and their position
distributions relevant to the frequency detunings of the
cavity mode and the coupling field are also experimental
investigated.
The energy levels and experimental setup are shown
in Fig.
1. The hyperfine structure in the D1 line of the
133
Cs atom is used for the Λ-type three-level EIT sys-
tem
[26]
composed of two lower states jaið6
2
S
1∕2
; F ¼ 4Þ,
jbið6
2
S
1∕2
; F ¼ 3Þ, and a common upper state
jcið6
2
P
1∕2
; F ¼ 4Þ [see Fig. 1(a)]. The coupling and probe
fields drive the transitions jai↔jci and jbi↔jci with
frequencies ω
p
and ω
c
and detunings Δ
p
¼ ω
p
− ω
ca
and
Δ
c
¼ ω
c
− ω
cb
, respectively. ω
ca
and ω
cb
are the corres-
ponding resonance frequency. A near-confocal optical
SC is composed of an input mirror M1 and an output
mirror M2 that have the same transmissivity (T
M1
¼
T
M2
¼ 0.5%) and the curvature radius (ρ
M1
¼
ρ
M2
¼ 150 mm). A piezoelectric transducer (PZT)
mounted on M2 is used for scanning and locking the cavity
length. The Cs vapor cell is 75 mm long with antireflection
(AR) coated end windows and is wrapped in μ-metal
sheets for magnetic field shielding and heat tape for con-
trolling its temperature. The vertical-polarized coupling
field is injected through a polarization beam splitter
COL 15(8), 081401(2017) CHINESE OPTICS LETTERS August 10, 2017
1671-7694/2017/081401(5) 081401-1 © 2017 Chinese Optics Letters