Application notes and frequently asked questions


Below are several application notes and white papers discussing various aspects of ultrafast laser pulse measurement, how to determine specifications for a pulse measurement system, and how to use a pulse measurement system.

Application Note AN005:

What do we mean by pulse measurement of an Ultrafast Laser?

Application Note AN010:

How do I determine the FROGscan specifications I need?

Application Note AN015:

What are the differences between FROGscan and single shot devices?


Below, we have tried to answer the most common questions visitors to our Web site may have. If you find that your question is not answered on this page, please contact us.
Why FROGScan?
  • FROG Scan is a real-time scanning FROG measurement system that uses a highly accurate, high speed mechanical optical delay that is at least 10X (ten times) faster than comparable optical delay lines. We seamlessly integrate a fast spectrometer with a 16-bit detector to provide unprecedented dynamic range on a commercial, off-the-shelf system.
  • The software that comes with FROG Scan, VideoFROGScan, uses our proprietary PCGP algorithm for pulse recovery, which is the most robust algorithm for SHG FROG retrieval.
  • VideoFROGScan is the easiest FROG software to use and is ideal for users who are new to pulse measurement. It is literally plug-and-play. An installation wizard guides you through the installation process and software setup.
  • VideoFROGScan has all the features you need to measure and analyze your pulses in real-time.
  • VideoFROGScan allows you to access retrieved pulses quickly and efficiently, in real-time, using third-party and custom software.
Why do I need to know the pulse chirp? Isn’t an autocorrelation good enough?

Well, I guess if all you need is some high-power, wide bandwidth photon hose, then you could just use a power meter and a spectrometer. BUT, if you want to determine peak intensities, need experimental repeatability, are doing pulse shaping, using nonlinear optics, then you need to have an accurate measurement of the pulse shape and chirp. No form of autocorrelation will provide the pulse shape or the chirp. Usually, autocorrelation fools you into thinking that your pulses are shorter than they really are and that they are smoother than they really are.

What do you mean that the complete range cannot be covered by a “Single Configuration”?

Covering the entire visible range and the entire range of pulse widths is not possible with any one spectrometer and any single doubling crystal. For example, a spectrometer that is ideal for pulse shaping will have a high resolution. However, if a spectrometer has a high resolution, then the spectral window will be too small to cover the spectral range needed for an OPA. Also, there are limitations to the bandwidth of the crystals that are used to generate the FROG signal. Typically, 3 crystals are required to cover the spectral range from ~450 nm to 1800 nm.

Even though we can’t cover the entire range, and you don’t want to buy a FROG Scan for each laser that you have, we have FROG Scan with the idea that you can swap out the crystals and the spectrometers depending on what your current needs are. Thus, FROG Scan can grow with your research group.

What are the differences between FROG Scan and single shot (SS) geometries?
  • FROG Scan is a scanning, multi-shot geometry. Rather than use two large beams that are crossed at an angle, FROG Scan uses two beams that are focused at the crystal. Advantages of FROG Scan:
  • More freedom in choosing the time window. SS devices have limited time windows that cannot be adjusted.
  • SS devices has limited time-bandwidth capability.
  • Better detector dynamic range. 16-bit vs. 8-bit so you can better handle low-level signals and see higher order phase distortions.
  • Better spectral resolution. You need good spectral resolution to measure long, transform-limited pulses, shaped pulses and high order phase distortions.
  • More flexibility. You can change FROGscan’s configuration to meet your needs now and in the future.
  • Disadvantages:
    –  You need a series of pulses.