New Method and CPA System for Controlling Carrier Envelope Phase of Low Repetition-Rate Pulses in Ultrafast Lasers

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Zenghu Chang, Ph.D.
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Eric Cunningham
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Yi Wu, Ph.D.
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John Miner
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Apparatus and Methods for Controlling Carrier Envelope Phase of Low Repetition Rate Pulses

US Patent 9,225,137
Advances in carrier-envelope phase stabilization of grating-based chirped pulse amplifiers
Laser & Photon. Rev. 4 , 4 (1), 160 - 177 (2010)

UCF researchers have pioneered a method for regulating the CEP of low-repetition rate CPA systems that allows the benefits of CEP control to be applied to more powerful ultra-fast laser systems. This development opens new avenues of scientific research and technological advancement using CEP-stabilized pulses with energies far higher than what is currently available.

Current limitations with CEP-controlled sources, including laser oscillators and high repetition-rate chirped-pulse amplifiers (CPAs), result from high pulse energies and peak intensities. Specifically, the low repetition-rate amplifiers used to create the orders of magnitude more pulse energy cannot be stabilized with the currently available technology, making them unfit for investigating and manipulating many strong-field processes.

Technical Details

This method involves the controlling CEP of low-repetition rate pulses in an innovative CPA system. Unlike in a typical CEP-locked CPA system, a low repetition-rate amplifier is seeded directly via a high repetition-rate amplifier and the beam is sampled right after the high repetition-rate amplifier, rather than after the compressor. This high repetition-rate 10% beam bypasses the low repetition-rate amplifier and then passes through the same compressor used by the low repetition-rate amplified pulses. Thus, all additional CEP errors derived from mechanical vibrations in the compressor are encoded in the 10% beam. When the CEP of the 10% beam is measured and the control loop signal is established, feedback is made using the same conditions in the low repetition-rate laser, which effectively locks both the low repetition-rate CEP and the high repetition-rate CEP. Within a double CPA system, where the front-end CPA operates at a high repetition rate and the back-end CPA operates at a low repetition-rate, the 10% sample of the beam is still taken after the compressor. Instead of sending this pulse to the CEP measurement setup, the beam is directed through both the low repetition-rate stretcher and the low repetition-rate compressor. With the CEP jitter of both stretchers and both compressors imprinted on the beam, its CEP value can be measured and the stretcher grating position in the front-end CPA can be used to stabilize the CEP of the entire system. Although this new method may increase the system’s cost, complexity, and dispersion, it does offer two significant advantages: 1) the low-repetition amplifier seeds with the highest energy possible because no energy is sacrificed to the sampling beam and 2) the available energy in the sampling beam is no longer limited to a fraction of the high-repetition beam energy, but rather the full energy is available for the measurement process.


  • CEP control applied to more powerful light sources
  • Less beam dispersion
  • Low-repetition amplifier seeds with highest energy possible


  • Pulse propagation through polar molecules
  • Cross-phase modulation
  • Ponderomotive surface-plasmon electron acceleration
  • Photoemission from metallic surfaces
  • Terahertz (THz) emission from the laser breakdown of air
  • Above-threshold ionization
  • High harmonic generation
  • Attosecond pulse generation