development of a system for high resolution spectroscopy with an optical frequency comb dept. of...
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![Page 1: Development of a System for High Resolution Spectroscopy with an Optical Frequency Comb Dept. of Applied Physics, Fukuoka Univ., JST PRESTO, M. MISONO,](https://reader035.vdocument.in/reader035/viewer/2022062305/5697c0151a28abf838cce08f/html5/thumbnails/1.jpg)
Development of a System for High Resolution Spectroscopy with an Optical Frequency Comb
Dept. of Applied Physics, Fukuoka Univ., JST PRESTO, M. MISONO, M. OKUBO, K. DAIRIKI
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AIM OF THE STUDY
Precise measure of optical frequency
molecular structure dynamics
High resolutionspectroscopy
Frequency shift, line broadening, line splitting, intensity anomaly, magnetic effect
Optical frequency
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EXCITED STATES OF NAPHTHALENE
3B3u(T1)
3B1u(T2)
3B1u
3B3u
1B1u(S1)
1B3u(S2)
1B3u
Singlet Triplet
Intersystemcrossing
1Ag(S0)
4b1u
1B1u
z (a)
y (c)(b)x
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PhotonicCrystal Fiber
Ti:Sapphire laser
Nd3+:YVO4laser
Stabilization
EXPERIMENTAL SYSTEM
Single modelaser
High finesse resonator
Stabilization
Frequencycounter
PhotoDiode Beat
measurement
High resolution spectroscopy
1 octave optical frequency comb
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HIGH RESOLUTION SPECTROSCOPY
Precise measure of optical frequency
molecular structure dynamics
High resolutionspectroscopy
Frequency shift, line broadening, line splitting, intensity anomaly, magnetic effect
Optical frequency
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DOPPLER-FREE TWO-PHOTON ABSORPTION SPECTROSCOPY
ν(1 - u /c) ν(1 + u /c)
Mirror Mirror
ν
u
hν(1 - u /c)
hν(1 + u /c)
2 hν
- Doppler free- Enhancement of light intensity for excitation- Selection rule is different from one photon absorption- Transition in UV region is excited by a visible laser- All molecules contribute to the signal independent of their velocities
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PZT
+-
Pump laser
Dye laser
IsolatorPD
PD
PD
λ/4
Color filter
Photomultiplier tube Photon counter
Com
pu
ter
EXPERIMENTAL SETUP
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OPTICAL RESONATOR AND SAMPLE CELL
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PRECISE MEASUREMENT OF OPTICAL FREQUENCY
Precise measure of optical frequency
molecular structure dynamics
High resolutionspectroscopy
Frequency shift, line broadening, line splitting, intensity anomaly, magnetic effect
Optical frequency
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1 OCTAVE OPTICAL FREQUENCY COMB
Frequency
Inte
nsi
ty
optical frequency
fCEO , frep Stabilization
Cs atomic clock in GPS satellites ・ Ultimate precision・ Low cost
Atomic clock Precise measure of frequency
fCEO frep (~ 100 MHz )
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GENERATION OF 1 OCTAVE OPTICAL FREQUENCY COMB
PhotonicCrystal Fiber
~ 20 fs
Repetition rate= 100 MHz
Frequencymode separation = 100 MHz
Ultra-short pulse laser
> 1 Octave~ 130 nm
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DETECTION OF fCEO
Frequency
Inte
nsi
ty
fCEO
f(2n) = 2nfrep + fCEO
Low frequency end of second harmonics
High frequency end of fundamental
2f(n) = 2nfrep + 2fCEO
Beat frequency fCEO
Fundamental
Second harmonics
(D. J. Jones, et al., Science 288, 635 (2000))
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CONTROL OF frep AND fCEO
Intensitymodulator
End mirror (Cavity length) : frep, fCEO
Pumping intensity : fCEO (, frep)
Outputcoupler
RF synthesizer
Cs atomic clock
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BEAT NOTE OF REPETITION AND OFFSET
Inte
nsi
ty [
10
dB
/div
]
0 120Frequency [MHz]
Beat by offsetBeat by repetition
fCEO
frep
40
dB
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STABILIZATION OF frep
99.999 988
100.000 012f r
ep [
MH
z]
0 600Time [s]
100.000 000
Gate time = 1 s
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STABILIZATION OF fCEO
25.00
Fre
que
ncy
[MH
z]
0 700Time [s]
26.12
Gate time = 1 s
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SUMMARY
• High resolution spectroscopy with a 1 octave optical frequency comb was studied to elucidate the structure and dynamics of polyatomic molecules.
• An experimental system for Doppler-free two photon absorption spectroscopy was developed.
• A stable mode locked Ti:Sapphire laser was developed and a 1 octave optical frequency comb was realized.
• The repetition rate (mode separation) of the 1 octave optical frequency comb were stabilized.
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HIGH PRECISION MEASUREMENT WITH OPTICAL FREQUENCY COMB
flaser = nfrep + fCEO+ fbeat
Frequency
Inte
nsi
ty
frepfCEO fbeat
flaser
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OPTICAL SYNTHESIZER
Single modelaser
RF Synthesizer
Opticalfrequency
combH
igh
reso
luti
on
spect
rosc
op
y
flaser
fsyn
flaser = fn + fsyn
FrequencyIn
ten
sity fn
fsyn
flaser fn+
1
frep - fsyn
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OPTICAL SYNTHESIZER
0 120Frequency [MHz]
fsyn frep - fsyn
0 120Frequency [MHz]
fsynfrep - fsyn
Frequency shift by AO modulator
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STABILIZATION SYSTEM FOR OPTICAL FREQUENCY COMB
PhotonicCrystal Fiber
DM
DMHM
BBO
PD: Photo diodeDM: Dichroic mirrorHM: Half mirror
fCEO
frep
Bandwidth 130 nmPulse width 20 fsRepetition rate 100 MHz
Ti:Sapphirelaser
Intensitymodulator
Cs atomic clock ( GPS satellite )
RF oscillator RF synthesizer
PD
PD
Prescaler TrackingOscillator
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frep
Bandwidth: 300 kHz
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FREQUENCY REFERENCE FOR STABILIZATION OF fCEO
25 MHz
Frequency
Sp
ectr
al In
tens
ity [1
0 d
B/d
iv]
[25 kHz/div]
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FREQUENCY REFERENCE FOR STABILIZATION OF fCEO
24.93
Fre
que
ncy
[MH
z]
0 2000Time [s]
25.00
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DEVELOPMENT OF HIGH RESOLUTION SPECTROSCOPY
precision ~ 10-11Free from limitation of experimental system
Doppler-free spectroscopy
precision ~ 10-6Doppler effect
precision ~ 10-8Measure of optical frequency
Optical frequency comb
This study
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~ 4550 cm-1
235 260[nm]
0.3 cm-1
Optical frequency
Laser light
Doppler-limited
Doppler-free
DOPPLER BROADENING