Carrier-envelope Phase Drift of Picosecond Frequency Combs from an Ultrahigh Finesse Fabry-Perot Cavity
P. Jójárt
1,2, A. Börzsönyi
1,2, R. Chiche
3, V. Soskov
3, A. Variola
3, F. Zomer
3, E. Cormier
4, K. Osvay
1,51Department of Optics and Quantum Electronics, University of Szeged, Hungary
2CE Optics Kft.,Hungary
3 Laboratoire de l’Accélérateur Linéaire, CNRS/IN2P3 Université Paris Sud, France
4 CELIA, Université de Bordeaux, France
5 ELI-Hu Nkft.,Hungary
Motivation
Carrier-envelope phase: relation between the carrier wave and the pulse envelope.
Propagation time
E-field
Carrier wave
Envelope
Use of CEP stabilized pulses
• High precision optical frequency and time measurements (by stable ”frequency-comb”)
• Attosecond physics and high-harmonic generation
• High precision refractive index measurements
• Calibration of astronomical mirrors
Methods to measure CEP drift
Requirements:
•Octave-broad bandwidth
•2ndharmonic generation
0 2 4 6 8 10 12
I (f )
f0 2f0 f
alap- harmonikus
első felharmonikus
fCEO Second harmonic
frequency comb Original
frequency comb
The f-to-2f scheme – the nonlinear way
f
1= f
CEO+ n ·f
repf
2= 2 · ( f
CEO+ m · f
rep) f
beat= f
2– f
1= f
CEOφ
CEO= 2π · f
CEO/ f
repH.R. Telle et al., Appl.Phys. B. 69, 327 (1999).
Multiple-beam interferometer – the linear way
Methods to measure CEP drift
Detection:
Spectrally resolved interfero- metry of subsequent pulses
Length stabilization:
Pattern inspection of a frequency-stabilized HeNe
Spectrograph
Piezo translator Ultrashort
pulse train Stabilized He-Ne
CCD
Pattern inspection
0.72 0.76 0.8 0.84 0.88 0
100 200 300 400
0.72 0.76 0.8 0.84 0.88
Intensity [a.u.]
Wavelength[μm]
Aplitude [a.u.]
Time [ps]
Spectral phase [rad]
(a) (b) (c)
0 1
0 1
0 1 2
-1 -2
Wavelength[μm]
Evaluation steps:
(1) Record interference pattern (2) FFT and filter the spectrum (3) Inverse FFT
(4) Complex angle gives the spectral phase difference (5) Fitting Taylor-series
(6) Calculate CEP = φ0– GD·ω0 L. Lepetit et al., JOSA B 12, 2467 (1995).
K. Osvay et al., Opt.Lett. 32, 3095 (2007).
0 400 800 1200 Time [s]
2 2.4 2.8 3.2 3.6 4
CEO phase of MBI [rad]
-40 0 40 80 120
FS wedge position [µm]
1.2 1.6 2 2.4 2.8
CEO phase of f-to-2f [rad]
1.2 1.6 2 2.4 2.8
CEP of f-to-2f [rad]
2 2.4 2.8 3.2 3.6 4
CEP of MBI [rad]
80 120 160
Time [s]
4 4.4 4.8 5.2 5.6 6
CEO phase of MBI [rad]
-40 0 40 80 120
FS wedge position [µm]
1.2 1.6 2 2.4 2.8
CEO phase of f-to-2f [rad]
-1 0 1
CEP change of f-to-2f [ra d]
-1 0 1
CEP change of MBI [rad]
Sinusoidal intracavity modification of CEP drift
Random intracavity modification of CEP drift
P. Jojart et al., Opt.Lett. 37, 836 (2012).
Oscillator CEP-stabilization
• Measure CEP signal with MBI
• Feedback to the oscillator
• CEP controlled by isochronic wedge pair
M.Gorbe et al., OL 33, 2704 (2008).
Stabilized oscillator Free running oscillator
Stabilization ON Stabilization OFF
-2 2
0
CEP drift [rad]
0 10 20 30
Time [min]
P. Jojart et al., CLEO 2012, CW1D.5
• Linear
• Scalable
• Bandwidth independent
• UV and far infrared lasers
• Applicable to a wide range of lasers:
• (sub-)picosecond lasers Multiple-beam interferometer – the linear way
Methods to measure CEP drift
Detection:
Spectrally resolved interfero- metry of subsequent pulses
Length stabilization:
Pattern inspection of a frequency-stabilized HeNe
Spectrograph
Piezo translator Ultrashort
pulse train Stabilized He-Ne
CCD
Pattern inspection
CEP drift detection in the ps regime
~1ps Pulsed laser
Electron beam Application: X-ray/gamma-ray generation by inverse Compton scattering
• Electron-beam collides with intense ultrashort pulses QTh1D.5
• Long cavity, ultrahigh finesse (28 000) Fabry-Perot resonator
• Oscillator locked to the FP cavity
• Frequency comb instabilities degrade coupling efficiency
2ps Ti:Sapph (75MHz)
• Locked to the FP cavity
• No control of the CEP drift in the feedback loop 2ps Ti:Sapph (75MHz)
• Locked to the FP cavity
• No control of the CEP drift in the feedback loop High-finesse Fabry-Perot cavity High-finesse Fabry-Perot cavity
Numerical feedback loop Pound-Drever-Hall scheme
• BW = 100-200 kHz Numerical feedback loop Pound-Drever-Hall scheme
• BW = 100-200 kHz
Multiple-beam interferometer High-resolution spectrograph (<2 nm bandwidth)
+ Frequency counter
Multiple-beam interferometer High-resolution spectrograph (<2 nm bandwidth)
+ Frequency counter
0 100 200 300 400
Time [s]
-1 -0.5 0 0.5 1
Fabry-Perot Coupling
-2 -1 0 1 2
CEP drift [rad]
0 200 400 600 800 1000
Time [s]
-1 -0.5 0 0.5 1
Fabry-Perot Coupling
-2 -1 0 1 2
CEP drift [rad]
Results
CEP drift modification by changing the crystal temperature
CEP drift modification
by changing the
pump power
Summary
• Carrier-envelope phase drift of picosecond pulses has been measured by multiple beam interferometry with an accuracy of 80 mrad
• CEP stabilization is now possible for mode- locked picosecond lasers
• Improved resolution of comb spectroscopy
• Better seed pulses for Compton light sources
Further developments
• Implementation of > 10 kHz line detectors
• Fast CEP stabilization of Ti:sapph oscillators
• Measurement and stabilization in NIR and other wavelength ranges
Thank you for your attention!
Acknowledgements:
The project was partially funded by “TÁMOP 4.2.2/B-10/1-2010-0012” and „TÁMOP-4.2.2.A- 11/1/KONV-2012-0060 – „Impulse lasers for use in materials science and biophotonics”, supported by the European Union and co- financed by the European Social Fund.
