Title: Stabilizing Carrier-Envelope Phase of KLS laser system
1Stabilizing Carrier-Envelope Phase of KLS laser
system
- Chengquan Li, Eric Moon, Zuoliang Duan, Jason
Tackett ,Zenghu Chang - April-05th-2006
2CE 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!
3Introduction what is CE phase?
Carrier-envelope phase (CE) The phase shift
between the peaks of the envelope and the closest
of the carrier wave.
4The origin of CE phase?
5Time-Domain Description of the Mode-Locked Pulse
Train
Fortier et al, IEEE J. Select. Topics Quantum
Electron., vol. 9, pp.1002-1010,2003.
6Frequency 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.
7How 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
9Experiment
- 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.
10Phase locking loop
Phase Detector f-to-2f, to detect the beat
signal f0 Loop filter Locking electronics VCO
voltage controlled oscillator (AOM,
femtolaser oscillator)
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12CE 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.
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14Interference between the white light and second
harmonic pulses
Phase of the Interference Signal
15Interference 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.
16Re-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
19Experiment result
Image ? digitized array ?FFT
20Averaged CEP drift
21CE Phase dynamics
Phase Locked
Phase Unlocked
22Slow 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.
23CE phase stabilization setup
24Temporal evolution of fringe pattern
oscillator locked, no slow feedback, 50 laser
shots
25Temporal evolution of fringe pattern
oscillator locked, with slow feedback, 50 laser
shots
26CE phase drift vs. time with and without
slow-drift feedback control
27Temporal evolution of fringe pattern
oscillator unlocked, 30 laser shots
28Summary
- 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.
29Thanks!
- Dr. Zenghu Chang
- Al Rankin
- KLS Members Mahendra Shakya, Shambhu Ghimire,
Chris Nakamura, and Steve Gilbertson - Dr. Washburn and Dr. Corwin
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