Carrier-envelop Phase Shift Only by Employing Linear Media

Technology #12013

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FIG. 1 is an illustration of a carrier and envelope. FIG. 2 is a graph that charts the change of the group delay over the relevant spectral range when varying the carrier-envelope phase by 2π.FIG. 3 is an exaggerated illustration of a “phase-plate” composite structure including a thick barium fluoride wedge and a thinner fused silica wedge. FIG. 4 is a graph that measures the average second order dispersion in the composite wedge structure and fit.FIG. 5 is a schematic illustration of the layout for an interferometric autocorrelator used to demonstrate the functionality of the plates.FIG. 6 is a graph showing a measured and retrieved autocorrelation revealing a pulse duration of 6 fs; the inset shows the laser spectrum on a linear scale.
Professor Franz Kaertner
Department of Electrical Engineering and Computer Science, MIT
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Richard Ell
Research Laboratory of Electronics, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Carrier-envelope phase shift using linear media

US Patent 7,839,905
Carrier-Envelope Phase Control by a Composite Plate
Optics Express, Vol. 14, Issue 12, pp. 5829-5837 (2006)


The invention can control the carrier-envelope phase of the optical light field and its temporal evolution inside a laser without change of the other pulse parameters (such as chirp, pulse width and pulse energy).

Problem Addressed

Traditional approach of changing phase or frequency via material insertion or removal also simultaneously alters the chirp and/or energy of the transmitted pulses.


The invention is a novel linear device, a composite glass plate, which changes the ratio of two materials with similar refractive indices and second order dispersion but different ratios of group and phase velocities. By doing so, the dispersion is practically kept constant, and the prism effect due to the slightly different refractive indices is negligible and consequently, the effect on pulse width, energy, spectrum, spatial chirp and CE frequency signal strength are minimized.


  • Minimizes impacts on chirp parameters while controlling CE phase or frequency of optical light
  • Can be very helpful in many experiments where a precise and “neutral” control of the CE phase is desirable