Rubidium atomic hyperfine filter for amplitude manipulation of ...

DAMOP08 Meeting of The American Physical Society
Rubidium atomic hyperfine filter for amplitude
manipulation of femtosecond frequency comb
Marin Pichler
marin.pichler@goucher.edu
Goucher College,
Baltimore, MD 21204 U.S.A.
Goran Pichler
pichler@ifs.hr
Ticijana Ban, Hrvoje Skenderović
Nataša Vujičić, Damir Aumiler, Silvije Vdović,
Institute of Physics
P.O.Box 304, HR-10000Zagreb, Croatia
http://Projekt2.ifs.hr
1

Outline
Femtosecond mode-locked laser pulse train excitation in rubidium 5 2 S 1/2 – 5 2 P 3/2
transition is used for direct mapping of the optical frequency comb
to rubidium atom velocity comb. The induced comb-like structure in
the rubidium ground state hyperfine level populations is monitored by
a weak cw scanning probe laser.
By introducing an additional rubidium cell, a hyperfine atomic flter is realized which
modifes the amplitude of the selected frequency comb lines.
The hyperfine optical flter can be a pure isotope 85 Rb or 87 Rb cell, in which case only
that isotope will affect the optical frequency comb.
2

Time and Frequency Domain of Mode-locked Laser
t
t 1
One pulse
E(
t)
( t)
e
N pulses
t
i c
Width: N / f(rep)
3

Experimenal Set-up for Modified DFCS
single-mode tuning range of up to 15 GHz
0.3 GHz/ms scanning rate
10 nm
10 THz
averaged power up to 700 mW
Spectral charasteristic
Intenzitet (rel. jed.)
300
250
200
150
100
50
0
xc = (806.6 ± 0.05) nm
w = (13.5 ± 0.1) nm
700 750 800 850 900
(nm)
1
P 0.44153
c
P 2
4
p

Rb Atoms Interacting with a fs Pulse Train
5

Absorption spectrum of rubidium D2 resonance line with hyperfine resolution
Making multi-Bennett holes
6

Rb Atoms Interacting with a fs Pulse Train
Fg=2
Fg=3
Fg=2
Experiment
Fg=1
7

Rb atomic
filter
Frequency comb modification
8

-500 0 500 1000 1500 2000 2500 3000 3500
Relative Frequency (MHz)
T F =36 O C
T F =30 O C
T F =24 O C
Transmission spectrum of two hyperfine lines
when the femtosecond laser frequency comb
was modified in the first Rb sapphire cell which
served as an atomic filter. Temperatures of the
first cell were 24 o C, 30 o C, and 34 o C.
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With a lock-in detetection method the sensitivity has increased by factor of 10
Fotodioda 1
Fotodioda 2
11

12
6
0
85,87
Rb filter, 795 nm fs laser
Frequency
96 o
C
67 o
C
47 o
C
33 o
C
27 o
C
24 o
C
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Conclusions
-We observed velocity selective optical
pumping. Velocity groups of Rb atoms in the
ground levels are separated by repetition rate
of the femtosecond laser oscillator.
-We observed velocity selective population
transfer into excited Rb atomic states
(multi-Bennett holes).
- We demonstrated imaging of optical
frequency comb onto the atom velicity comb
• very sensitive method probably appropriate to
measure some fundamental physical and
chemical features of Rb atoms in vapor phase
- Rb-Rb resonance broadening
- saturation processes
- influence of external magnetic and electric field
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80 MHz
Freq. comb
Rb 795 nm D1 detection of ground state population
D1
OUTLOOK
2
812 MHz
1
2
1
267 MHz
157 MHz
72 MHz
D2
6835 MHz
3
2
1
0
80 MHz
Freq. comb
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Rubidium atom
795nm
780nm
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87 Rb - pure isotope cell
Rb D1 795 nm
Optical Thickness
0,12
0,11
0,10
0,09
0,08
0,07
0,06
0,05
0,04
0,03
0,02
0,01
0,00
D1
2
812 MHz
1
2
1
Frequency
267 MHz
157 MHz
72 MHz
D2
6835 MHz
3
2
1
0
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Optical Thickness
0,12
0,11
0,10
0,09
0,08
0,07
0,06
0,05
0,04
0,03
0,02
0,01
0,00
87 Rb
85 Rb
85 Rb
Frequency
87 Rb
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Cancellation of the coherent accumulation in rubidium
atoms excited by a train of femtosecond pulses
PRA, 76 043410 (2007).
Femtosecond laser pulse train effect on Doppler profile
of cesium resonance lines
EPJD 41, 447 (2007).
Mapping of the optical frequency comb to the atom
velocity comb
PRA 73, 043407 (2006).
Velocity selective optical pumping of Rb hyperfine lines
induced by a train of femtosecond pulses
PRL 95, 233001 (2005).
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Thank you!
Supported by the Ministry of Science of
the Republic of Croatia and
the Alexander von Humbolt Stiftung,
Germany
Brijuni2009.ifs.hr
FEMTO
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