Multi-Picosecond and Nanosecond FROGs

Filling a gaping technological hole that has existed for almost 50 years, Swamp Optics offers an elegant device for measuring pulses up to 4 nanoseconds long!

Partially as a result of single-shot FROG measurements, femtosecond laser pulses are arguably the best characterized type of light in the world. But what about the ~1 nanosecond pulses that actually gave birth to the field of pulse measurement to begin with? Nanosecond and many-picosecond pulses have critical applications, including materials processing, welding, machining, surgery, ranging, remote sensing, military, and basic science. But in pressing to ever shorter timescales, the measurement of these longer, less exotic pulses was nearly forgotten. Also these longer pulses are typically very complex in time and may be the least stable laser pulses available. These lasers also suffer from the poorest specifications, making purchasing decisions very difficult. Very expensive ultrahigh-bandwidth oscilloscopes and streak cameras can now yield blurry black-and-white images of them, but few can afford these devices, and a more complete measurement would be much better.

 

Swamp Optics has finally solved this problem. Swamp Optics nanosecond FROG measures the complete intensity and phase of pulses tens of picoseconds to a few nanoseconds long, yielding a full-color high-definition picture of even a single pulse.

 

The trick is to use the massive pulse-front tilt induced by an etalon. The pulse is first split into two halves (indicated in red and blue in the figure below) by a large-apex-angle prism. A cylindrical lens focuses both pulses to lines at the clear edges of an etalon. Inside the etalon, the pulses undergo multiple reflections and hence massive tilt (illustrated in blue for one of the pulse halves). Another lens then images the etalon onto a nonlinear medium, crossing the beams to yield a single-shot autocorrelation. This lens also focuses the pulses in the vertical direction. The nonlinear-optical signal pulse then enters an etalon spectrometer and camera (not shown).

Massive pulse tilt using an etalon and the resulting single-shot nanosecond FROG. Inset upper left: measured and retrieved traces of a micro-disk laser pulse. Inset lower right: retrieved micro-disk laser pulse.

3D model of the planned nanosecond FROG apparatus.

 

Read nanosecond FROG related articles (Complete single-shot measurement of arbitrary nanosecond laser pulses in time).

 

 

Nanosecond FROG at a glance

 

  • Yields the pulse intensity and phase vs. time
  • Yields the pulse spectrum and spectral phase
  • Measures the beam spatial profile
  • Makes no assumptions about the pulse
  • Requires minimal alignment
  • High sensitivity
  • Real-time pulse retrieval (10pps)
  • Minimal effort, weight, size, and cost

 

Download the multi-ps and ns FROG Kit Brochure and Typical-Spec Sheet.

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