Configuring GRENOUILLE

Using GRENOUILLE is simpler than you ever imagined! But there are some options to consider when purchasing it.

Using GRENOUILLE Alone

You can simply display the trace from GRENOUILLE's camera on a video monitor, and, since it's a spectrogram, you can tell a lot by just looking at it. For example, since it's a spectrally resolved autocorrelation, just visually integrating over wavelength (the vertical axis) yields the autocorrelation. Or, better, the trace width along the delay axis is proportional to the pulse length, and the trace width along the wavelength axis is proportional to the spectral width (the proportionality factors are the same autocorrelation factors you're used to). Also, the trace area is proportional to the pulse time-bandwidth product. And, of course, at the flip of a switch, GRENOUILLE also provides the beam spatial profile.

Combining GRENOUILLE with Pulse Analysis Tools

No algorithm exists for retrieving the intensity or any other quantitative information from an autocorrelation, but it's possible to retrieve an incredible amount of useful quantitative information from a GRENOUILLE trace. Indeed, inexpensive software exists that can compute and display the pulse intensity vs. time, the phase vs. time, the spectrum, the spectral phase, the spatial profile, the spatial chirp, and pulse-front tilt. And, of course, you can also get the autocorrelation (which is trivially derived from the intensity, but there's no need to compute it if you already have the intensity!).

Fig. 1. Setup for using GRENOUILLE. The devices labeled in black are already in your lab, and those labeled in magenta represent devices or software that will give you the most detailed and effortless measurements of your ultrashort pulses ever available.

To take advantage of the extended information available from a GRENOUILLE trace, it's necessary to get the pulse trace into a computer. This involves using a frame-grabber (basically, a board that fits in your computer and which grabs a frame from GRENOUILLE's camera) and some computer code to analyze the trace. Because GRENOUILLE provides both temporal and spatial pulse information, it's best to use both temporal-profile (FROG) code and spatial profile code.

As described below, there is a third-party that provides the frame-grabber hardware and software solution for the most informative measure of an ultrashort laser pulse ever.

Femtosoft Technologies' QuickFrog

QuickFrog continuously monitors a live FROG trace and applies the FROG retrieval algorithms in real time, while simultaneously displaying the results of the retrieval. It retrieves all spatio-temporal information available from GRENOUILLE devices, including intensity and phase vs. time; spectrum and spectral phase vs. time; spatial chirp; and pulse-front tilt. Temporal and spatial operating modes let you change how QuickFrog handles your trace: for analysis (where the FROG algorithms are applied to the data) or in a straight-through mode that enable you to align the beam and see its spatial profile.

The QuickFrog package includes a Firewire frame grabber that connects directly to the camera in your GRENOUILLE.