Transcript Optical Resonators for Frequency Combs

Frequency Comb Vernier
spectroscopy
Frequency Comb Vernier Spectroscopy
C. Gohle, A. Renault, D.Z. Kandula, A.L. Wolf, W. Ubachs,
K.S.E. Eikema
Laser Centre, Vrije Universiteit Amsterdam, DeBoelelaan 1081, 1081 HV Amsterdam
A. Ozawa, B. Bernhardt, B. Stein, A. Schliesser, Th.
Udem, T.W. Hänsch
Max-Planck-Institut für Quantenoptik, Hans-Kopfermannstraße 1, 85748 Garching
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Outline
• Introduction:
– Frequency combs and Optical resonators
Frequency Comb Vernier Spectroscopy
• XUV comb generation
• Optical vernier spectroscopy
• Outlook
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Frequency Comb Vernier Spectroscopy
Frequency combs and optical
resonators
Frequency Combs
E(t)=A(t)eiwct = S Am e-imwrt-iwct
m=-
1n = n1r + 1CE , 1CE < 1r, 7=2 1CE/1r
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Frequency Comb Vernier Spectroscopy
+
Example: Hydrogen
Frequency Comb Vernier Spectroscopy
f(1S-2S) = 2 466 061 102 474 851(34) Hz
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Fabry perot resonators
Frequency Comb Vernier Spectroscopy
light source
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… provide stable references
• Narrow Markers in
Frequency space
Frequency Comb Vernier Spectroscopy
– If high finesse
• High stability
– ~10-15 @ 1 s
– Hz linewidth @ 1 PHz
– ~10-16m length
stability
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… enhance nonlinear conversion
• Pc=F/
Frequency Comb Vernier Spectroscopy
– Output power grows
with finesse2 or
higher!
• Example:
– SHG 560nm->280nm
– 900mW driving power
– 20% conversion:
900mW->200mW
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… enhance sensitivity
• Cavity absorbtion
spectroscopy
/ 

¡ r
F
T 
¡
A
¼
• Cavity ring down
– Intrinsically robust
– Can be broad band
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Frequency Comb Vernier Spectroscopy
– Increased interaction
length
– Intrinsically narrow
band
Response function
Frequency Comb Vernier Spectroscopy
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Cavity enhanced HHG
– No dispersion
• Electric field in the pulse envelope has to look the same for
both pulses -> equidistant modespacing
– frep = fFSR
• Timedelay between pulses = cavity roundtrip time
– fCEO matches
• HHG inside the resonator
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Frequency Comb Vernier Spectroscopy
• Obvious requirements
XUV Output
Circ. Power 40W, intensity in the focus 5 x 1013 W/cm2
Frequency Comb Vernier Spectroscopy
C. Gohle et al., Nature, 436, 234 (2005)
R. J. Jones et al., PRL, 94, 193201 (2005)
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Coherence (of the 3rd harm.)
Frequency Comb Vernier Spectroscopy
C. Gohle et al., Nature, 436, 234 (2005)
R. J. Jones et al., PRL, 94, 193201 (2005)
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… coherence!
odd harmonics
Frequency Comb Vernier Spectroscopy
I (f )
f
log [I (f ) ]
I (f )
plateau
cut-off
high harmonic radiation
f
frequency comb
(probably)
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f
Possible Applications
• Direct frequency comb spectroscopy in the
XUV
• Compact coherent XUV source for
interferometry
• High repetition rate high intensity source for
coincidence measurements
• BUT: power still low!
• And many technical problems
•
Use an amplifier!
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Frequency Comb Vernier Spectroscopy
– It is cw, so no transients
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Frequency Comb Vernier Spectroscopy
Frequency Comb Vernier
Spectroscopy
Direct comb spectroscopy, the good
I(1)
300 THz
1
3,000,000 narrow band modes with
0.3 mW power
Simultaneously tuneable and referencable
1
Marian et al, PRL, 95, 023001 (2005)’
V.Gerginov et al. Optics Letters, 30, 1734 (2005)
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Frequency Comb Vernier Spectroscopy
300 THz band width
and 100 MHz mode
spacing.
… and the bad
• Large background
• Aliasing
– Spectra difficult to interpret
• Small power per mode
– Small signal
– Nonlinear (dopplerfree) spectroscopy
difficult
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Frequency Comb Vernier Spectroscopy
– for absorbtion measurements
– Causing stark shifts
... the remedy
Frequency Comb Vernier Spectroscopy
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Data
Single scan
(10ms)
•
Blue box:
unique data
•
Red boxes:
identified
features
•
Gaussian PSF
much larger
than airy !
Brightness~Int
egral of airy
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Frequency Comb Vernier Spectroscopy
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arXiv:0706.1582v1 [physics.optics]
O2 magnetic dipole intercombinationline (760nm)
Frequency Comb Vernier Spectroscopy
Red:HITRAN data
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Results*
Absorbtion:
•Noisefloor
O2 A-Band
Frequency Comb Vernier Spectroscopy
< 10-5/cm (100 Hz)1/2=
< 10-6/cm Hz1/2 (shotnoise: <10-8)
•> 4 THz bandwidth
1 GHz sampling (>4000 res.
Datapoints in 10 ms)
•Quantitative agreement in
Amplitude and Frequency
to HITRAN** database
Phase:
- agrees with expectations (disp. features)
-not optimized for good phase sensitivity
-Still <0.1 mrad/Hz1/2
* arXiv:0706.1582v1 [physics.optics]
** Rothman, L. S. et al., J. Quant. Spect. Rad. Trans., 96, 139-204 (2005)
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… and the bad
• Large background
• Aliasing
– Spectra difficult to interpret
• Small power per mode
– Small signal
– Nonlinear (dopplerfree) spectroscopy
difficult
… may be possible
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Frequency Comb Vernier Spectroscopy
– for absorbtion measurements
– Causing stark shifts … reduced
Thanks
Akira Ozawa
(fs-Cavities)
Birgitta Bernhardt
Jens Rauschenberger
Theodor W. Hänsch
Albert Schliesser
Thomas Udem
Funding:
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Frequency Comb Vernier Spectroscopy
Maximilian Herrmann
(Ion Traps)
Sebastian Knünz
Valentin Batteiga
(Hydrogen)
Nikolai Kolachevski
Janis Alnis
Arthur Matveev
Elisabeth Peters