Stabilizing Carrier-Envelope Phase of KLS laser system - PowerPoint PPT Presentation

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Stabilizing Carrier-Envelope Phase of KLS laser system

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Title: Stabilizing Carrier-Envelope Phase of KLS laser system


1
Stabilizing Carrier-Envelope Phase of KLS laser
system
  • Chengquan Li, Eric Moon, Zuoliang Duan, Jason
    Tackett ,Zenghu Chang
  • April-05th-2006

2
CE Phase Stabilization
  • Important for experiments utilizing identical
    few-cycle laser pulses
  • CE Phase-dependent research
  • Can use a stabilized frequency comb to perform
    spectroscopy.
  • More applications to come!

3
Introduction what is CE phase?
Carrier-envelope phase (CE) The phase shift
between the peaks of the envelope and the closest
of the carrier wave.
4
The origin of CE phase?
5
Time-Domain Description of the Mode-Locked Pulse
Train
Fortier et al, IEEE J. Select. Topics Quantum
Electron., vol. 9, pp.1002-1010,2003.
6
Frequency Comb and Laser Spectrum1
Mode-Locked Pulse Train in the Frequency Domain
1 Fortier et al, IEEE J. Select. Topics Quantum
Electron., vol. 9, pp.1002-1010,2003.
7
How to stabilize the CE Phase (drift)?
Beating the second harmonic and fundamental
frequency combs of the laser yields a frequency
proportional to the change of the
carrier-envelope phase.
2fn
8
  • The CE phase change can be controlled by locking
    the offset frequency, f0, to a known frequency.
  • In the case of the KLS, f0 is set equal to
    one-quarter of the repetition rate of the
    oscillator.

The every 4th pulses from the oscillator have a
identical CE Phase
9
Experiment
  • The KLS utilizes a Kerr-Lens Mode locked
    TiSapphire oscillator emitting a 77 million
    pulses per second.
  • The pulses are roughly 12 fs at the output of the
    laser and carry nJ energy per pulse.
  • The oscillator is the starting point for the
    self-referencing technique.

10
Phase locking loop
Phase Detector f-to-2f, to detect the beat
signal f0 Loop filter Locking electronics VCO
voltage controlled oscillator (AOM,
femtolaser oscillator)
11
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12
CE Phase Stability After Pulse Amplification2
  • A second f-2f interferometer after the KLS
    amplifier provides a means for quantifying the CE
    phase stabilization stability.
  • 10 of the KLS amplifier output is sent to the
    experimental setup.
  • White-light is generated in a sapphire plate and
    a BBO crystal provides second-harmonic generation.
  • 2 Baltuska et al.,IEEE J. Select. Topics
    Quantum Electron., vol. 9, pp. 972-989, 2003.

13
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14
Interference between the white light and second
harmonic pulses
Phase of the Interference Signal
15
Interference between the white light and second
harmonic pulses
Phase of the Interference Signal
The shot-to-shot change of this phase can be
monitored by the second f-2f setup.
  • 2 Baltuska et al.,IEEE J. Select. Topics
    Quantum Electron., vol. 9, pp. 972-989, 2003.

16
Re-contraction of phase (FTSI) step 1 linear
scanning
17
Step 2 Fourier transform and sideband filtering

18
Step 3 Inversed Fourier transform
Relative phase drift
19
Experiment result
Image ? digitized array ?FFT
20
Averaged CEP drift
21
CE Phase dynamics
Phase Locked
Phase Unlocked
22
Slow feedback control wanted!!
  • Using f-to-2f, the CE phase of oscillator can be
    locked over 3 hours
  • Fast dynamics founded in the CE phase drift in
    amplified laser pulses
  • Low frequency quasi-periodic CE phase drift in
    amplified laser pulses.

23
CE phase stabilization setup
24
Temporal evolution of fringe pattern
oscillator locked, no slow feedback, 50 laser
shots
25
Temporal evolution of fringe pattern
oscillator locked, with slow feedback, 50 laser
shots
26
CE phase drift vs. time with and without
slow-drift feedback control
27
Temporal evolution of fringe pattern
oscillator unlocked, 30 laser shots
28
Summary
  • Using f-to-2f interferometer, we stabilized the
    change of the carrier-envelope phase of the KLS
    over 3 hours.
  • The CE phase drift was measured using a second
    f-to-2f interferometer.
  • Under the slow feedback control, the Ce phase
    drift was suppressed into 100 mrad range for
    several minutes.

29
Thanks!
  • Dr. Zenghu Chang
  • Al Rankin
  • KLS Members Mahendra Shakya, Shambhu Ghimire,
    Chris Nakamura, and Steve Gilbertson
  • Dr. Washburn and Dr. Corwin

30
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