Pulse Duration. Phase. Spectrum.
FROG Reconstructs the Entire Pulse.
Our FROG systems (Frequency-Resolved Optical Gating) are designed for the complete characterization of ultrashort laser pulses. They reconstruct the electric field of the laser pulse and determine its temporal intensity, spectral intensity, and spectral phase.
This makes it possible to reliably analyze pulse duration, chirp, dispersion, and other pulse characteristics. The result is a complete picture of your laser pulse, providing the basis for targeted laser system optimization, reproducible measurement results, and a well-founded assessment of actual pulse quality.
When FROG Systems Make Sense
The properties of an ultrashort pulse laser are usually well known at the laser output. On the way to the experiment, however, compressors, mirrors, lenses, and other optical components alter the laser pulse. Dispersion and nonlinear effects can significantly affect its temporal and spectral structure.
In post-compressed laser systems, complex optical setups, or nonlinear optics applications in particular, pulse duration alone is often not sufficient. What matters is which pulse properties are actually present at the point of use.
Key Features of Our FROG Systems
Reconstruction of the full electric field of ultrashort laser pulses, including temporal and spectral intensity as well as phase
Two specialized measurement principles for different applications – from characterizing individual pulses to measuring low pulse energies
Hot-swappable spectrometer modules allow adaptation to different wavelength ranges without replacing the entire system
Simple alignment, intuitive software, and reliable reconstruction algorithms enable reproducible pulse characterization with minimal effort
FROG Systems – Characteristics and Design
For the characterization of ultrashort laser pulses, TOPAG offers specialized FROG systems (Frequency-Resolved Optical Gating) from our partner Femto Easy, covering a range of requirements in research, development, and industrial applications. Depending on pulse energy, repetition rate, and measurement task, two measurement principles are available: Fast FROG for single-shot characterization of individual laser pulses, and MS-FROG for highly sensitive multi-shot measurement of low-energy pulses.
Both systems provide complete characterization of ultrashort laser pulses by reconstructing the electric field, determining temporal intensity, spectral intensity, and spectral phase. This allows key pulse properties such as pulse duration, chirp, and dispersion to be reliably analyzed and laser systems to be optimized in a targeted way.
Fast FROG – Single-Shot Characterization of Individual Laser Pulses
The Single-Shot Fast FROG enables complete characterization of individual ultrashort pulses in a single measurement. Because each laser pulse is captured individually, it can be analyzed even under pulse-to-pulse fluctuations or unstable operating conditions.
The system is particularly well suited to amplifier systems, low-repetition-rate lasers, and applications where the actual properties of every single pulse are critical.
Typical Applications
- CPA and amplifier systems
- Low repetition rates
- Pulse-to-pulse analysis
- Post-compressed laser pulses
- Nonlinear experiments
MS-FROG – Highly Sensitive Multi-Shot Pulse Characterization
The Multi-Shot FROG (MS-FROG) was developed for the precise characterization of low-energy femtosecond pulses. By measuring across multiple laser pulses, it improves the signal-to-noise ratio, enabling reliable measurements even at very low pulse energies.
The system enables pulse characterization in the pJ-to-nJ range and is particularly well suited to high-repetition-rate laser sources, oscillators, and applications with limited pulse energy.
Typical Applications
- High-repetition-rate femtosecond lasers
- Oscillator-based laser systems
- Low-pulse-energy laser sources
- Laser development and production
- Quality control of ultrashort pulses
Flexible Wavelength Coverage Through Modular Spectrometers
Our FROG systems use interchangeable MISS spectrometer modules that allow quick adaptation to different wavelength ranges.
This means a single measurement system can be used flexibly across different ultrashort pulse lasers, laser sources, and future experiments. The modular architecture makes the system easy to expand and reduces the effort involved when measurement requirements change.
Key Specifications of Our FROG Systems
The Single-Shot Fast FROG is based on second-harmonic generation and is available in six models covering pulse duration ranges from 4 fs to 10 ps across a broad spectral range. The Fast FROG stands out for its wavefront-division technique, its use of a Mini Imaging Spectrometer (MISS), and its ease of use and versatility.
The Multi-Shot FROG (MS-FROG) is preferably used for pulse energies in the pJ-to-nJ range, covering durations from 3 fs to 80 ps. It features spectrometers developed specifically for FROG measurements and manufactured in-house by Femto Easy, ensuring high spectral resolution and excellent performance in pulse characterization.
Single-Shot Fast FROG
Frequency-Resolved Optical Gating for individual pulses
- Wavelength: 480–2100 nm
- Pulse duration: 4 fs–10 ps
- Repetition rate: single-pulse up to 125 kHz
- Features: achromatic and non-dispersive
Multi-Shot FROG
Frequency-Resolved Optical Gating for repetitive fs and ps pulses
- Wavelength: 500–2100 nm
- Pulse duration: 3 fs–80 ps
- Repetition rate: 100 Hz to GHz
- Features: extremely high temporal resolution down to 50 as
Options for the Single-Shot Fast FROG
A range of options allows the single-shot Fast FROG to be configured for different laser sources, spectral ranges, and ultrashort-pulse characterization requirements:
- Additional SHG crystals: Extend the wavelength range of FROG pulse measurement with interchangeable plug-and-play SHG crystals
- Additional MISS spectrometer: A second MISS imaging spectrometer for quick adaptation to different spectral ranges and laser wavelengths
- Enhanced Detection: Higher-performance detection for improved temporal and spectral resolution, as well as single-pulse analysis up to 125 kHz
- High Dynamic Range: Extends signal acquisition from 12 to 16 bits for a wider dynamic range in FROG measurements (not compatible with pure single-shot measurements)
- Low Energy: Increased FROG sensitivity for reliable characterization of low-pulse-energy lasers
- Phase Loop: Software option for spectral phase feedback with a compatible pulse shaper, enabling active optimization of ultrashort laser pulses
- Phase Matching: Optimizes SHG phase matching for different central wavelengths and the best possible signal quality
- Pulse Front Tilt & Spatial Chirp: Analyzes spatio-temporal couplings such as spatial chirp and pulse front tilt for more accurate pulse reconstruction
- Small Beam: Integrated module expands the input beam to the size required by the Fast FROG (for small laser beams)
- Trigger: External synchronization for precise single-shot pulse measurements up to 36 kHz, or up to 125 kHz with Enhanced Detection
Options for the Multi-Shot FROG
A range of options allows the Multi-Shot FROG to be flexibly adapted to different laser sources, wavelengths, and ultrashort-pulse characterization requirements:
- Additional SHG crystals: Extend the wavelength range of FROG pulse measurement with quick-change plug-and-play crystals
- Additional MISS spectrometer: A second MISS imaging spectrometer enables measurement in additional spectral ranges and quick switching between different laser wavelengths
- Fiber-coupled input: An optional fiber input module allows the Multi-Shot FROG to switch flexibly between free-space and fiber input, without realignment
- Low Energy: Increased sensitivity to low-energy laser pulses enables reliable characterization even at very low pulse energies
- Low Repetition Rate: Optimized synchronization for low-repetition-rate lasers (recommended for repetition rates below 200 kHz)
Any Open Questions?
We're happy to advise you or arrange a demo measurement
What Users Say About Our FROG Systems
FAQ – FROG Systems for Ultrashort Laser Pulses
What Is a FROG System?
A FROG system (Frequency-Resolved Optical Gating) is a measurement instrument for the complete characterization of ultrashort laser pulses. Unlike a simple pulse duration measurement, a FROG system determines the full electric field of a laser pulse. In addition to pulse duration, this reconstructs the temporal intensity, spectral intensity, and spectral phase. From this information, properties such as chirp, dispersion, and other pulse characteristics can be reliably determined.
What Does Frequency-Resolved Optical Gating Mean?
Frequency-Resolved Optical Gating (FROG) is an established measurement technique for characterizing ultrashort laser pulses. It records a frequency-resolved nonlinear signal known as the FROG trace. Numerical reconstruction algorithms then use this trace to calculate the electric field of the laser pulse. The technique provides both the intensity and the phase of the pulse and is now one of the standard methods used in ultrafast laser diagnostics.
What Is the Difference Between FROG and an Autocorrelator?
An autocorrelator primarily provides information about pulse duration. Its analysis often requires assumptions about the pulse shape, and the spectral phase of the laser pulse remains unknown.
A FROG system, by contrast, reconstructs the complete electric field of the pulse. In addition to pulse duration, it also determines temporal intensity, spectral intensity, and spectral phase. This makes it possible to unambiguously analyze chirp, dispersion, and complex pulse shapes. For demanding research and development applications, FROG therefore provides significantly more information than a simple autocorrelation measurement.
When Should You Use the Fast FROG?
The Fast FROG is well suited to applications that require the complete characterization of individual laser pulses. Because the measurement is captured in a single laser shot, the system is particularly useful for amplifier systems, low-repetition-rate lasers, and applications involving pulse-to-pulse fluctuations. Typical use cases include CPA laser systems, post-compressed pulses, and nonlinear optics experiments.
When Should You Use the MS-FROG?
The MS-FROG is designed for characterizing low-energy, high-repetition-rate laser pulses. Its multi-shot measurement principle uses multiple pulses to build up the signal, allowing reliable measurement of very low pulse energies in the pJ-to-nJ range. The system is especially well suited to femtosecond oscillators, laser development and production environments, and high-repetition-rate applications.
How Is the Spectral Phase of a Laser Pulse Measured?
The spectral phase cannot be measured directly with a spectrometer. Instead, it is reconstructed using complete pulse characterization techniques such as Frequency-Resolved Optical Gating (FROG). This works by first recording a frequency-resolved nonlinear signal. Specialized reconstruction algorithms then use this signal to calculate the complete electric field of the laser pulse, including its spectral phase. Knowing the phase is essential for reliably determining chirp, dispersion, and the actual pulse shape.
Can I Test a FROG System Before Purchasing?
Yes. We’re happy to arrange a demo unit for you to test at your own facility. Please contact us by email or via the contact form on our website.