A Dispersion-Free, Automatically Phase-Matched, and Broad Spectral-Band Femtosecond Autocorrelation Technique

The technique uses second harmonic generated (SHG) autocorrelation from metal surfaces to characterize the femtosecond laser pulses.

This invention offers a technique to temporally characterize ultra short (femtosecond) laser pulses. It is simple in its design and has very broad spectral bandwidth.

Most current techniques rely on the use of a nonlinear crystal to generate autocorrelation non-linear signal. These techniques, although straight forward, have a number of limitations. The most significant disadvantage stems from the phase-matching requirement, which limits the spectral band-width of pulse characterization. In addition, the non-linear crystals are usually quite expensive, especially those made for this application which must be very thin to reduce dispersion.
The technique disclosed here uses autocorrelation second harmonic generated (SHG) from metal surfaces which provides a number of unique advantages. First, since SGH is generated from a few top surface layers, the phase-matching condition is automatically fulfilled. Second, the measurement is virtually dispersion free since only a few atomic layers are involved. Third, SHG can be generated from a metal surface over and extremely broad wavelength range. In principal, SHG signal can be produced from far infrared to deep ultraviolet and up to plasma frequency of the metal used.  This broad spectral bandwidth is the most significant advantage over the existing techniques.

URV Reference Number: 2-11150-05029
Patent Information:
For Information, Contact:
John Fahnervihtelic
Senior Licensing Manager
University of Rochester
Chunlei Guo