High-Performance Real-Time FROG Pulse-Retrieval Software

While a great deal can be surmised directly from the spectrogram that is the measured FROG trace, it's helpful to have pulse-retrieval code to determine the pulse intensity and phase vs. time, the spectrum and spectral phase, and the stability of the pulse train (if a multi-shot measurement was made).  Fortunately, we have comprehensive real-time pulse-retrieval programs for all Swamp Optics FROGs and GRENOUILLEs developed by the original inventor of FROG code himself (Rick Trebino) and implemented by professional programmers, and engineered for ease of use.  The program continuously monitors the measured FROG trace and applies the FROG pulse-retrieval algorithm in real time, while simultaneously displaying the results of the retrieval.

 

The program retrieves all spatio-temporal information available from Swamp Optics' FROGs and GRENOUILLEs, including:

 

 

 

All information about your device required by the FROG program, including the device calibration, is stored in the FROG or GRENOUILLE hardware and immediately read by the FROG program, so all you need to do is to simply connect the USB cable to your computer, start the program, and you're ready to start measuring pulses.

 

FROG-program front-panel all-information display showing measured pulses from a frequency-doubled fiber laser.

 

Program Temporal and Spatial Operating Modes

 

Temporal and spatial operating modes let you change how the FROG program handles your trace.  In the temporal mode, the FROG algorithm retrieves the pulse from the measured trace, and the laser pulse intensity and phase are recovered.  In the spatial mode, the code displays the beam spatial profile.  The spatial-profile mode can also be used to align the beam into the device in single-camera models.  For two-camera FROG and GRENOUILLE models, the FROG program can display both measurements simultaneously.

Additional Important Features of Our FROG Code

In addition to the above measurements, our FROG code also provides a full range of metrics, including:

 

 

The trace-area-normalized FROG error, G', is an important improvement over previous FROG programs.  The old "FROG error" (G) is the rms difference between the measured and retrieved traces divided by the number of points in the trace.  It was first defined in the early 1990s by Rick Trebino and used by him mainly for algorithm development and never was intended to be used in experimental measurements.  But it was, and, now, over two decades later, it still is, even though it isn't appropriate for this application.  G' is an improved measure of measured- and retrieved-trace agreement.  G' is the rms difference between the two traces, normalized by the trace area, not the number of points in the trace, as in G in more primitive versions of the FROG code.  Unlike G, G' can be compared to—and should be equal to—the actual noise in the trace.  If G' exceeds the trace data average noise value, then it is likely that the measured pulse train is unstable.  As there is no independent check for pulse-train instability (FROG is the only known check for this problem!), this is an invaluable statistic!

 

In addition, the FROG program automatically checks for potential problems in the set up, such as saturation of the camera due to sending too much power into the FROG or GRENOUILLE.

 

The program also automatically adjusts for longer or shorter pulses, achieving the optimal trace window for any given pulse.

 

And it automatically subtracts off any unwanted background.  This is important for optimal results, as over-subtraction can yield a pulse that is too short and too narrowband, but under-subtraction can yield incorrect noisy background to the measured pulse's intensity vs. time.

 

 

The code can save the current state of the retrieval at any time. This includes:

 

 

 

From a very user-friendly interface, the code can also:

 

 

 

The spatial-profile camera-display window includes:

 

 

Computer System Requirements

Windows XP Professional or later.

 

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