IRis-F1 Dual-comb Spectrometer

  Normal Operations

The IRsweep IRis-F1 spectrometer uses a dual frequency comb laser source to provide high signal-to-noise measurements with microsecond time resolution.

This spectrometer is an excellent complement to broadband FT-IR measurements where information about the dynamics of the system of interest is limited by the useful time resolution of rapid-scan measurements or by the reproducibility requirements of step-scan measurements.

Time-Resolved Measurement Modes

There are a number of different measurement modes with implications for time resolution.

Static Measurement

Closest to a traditional FT-IR rapid-scan measurement, but with faster measurement rates and times.

  • Traditional background measurement
  • Sample measurements can be repeated as needed
  • Rapid multiple static acquisition limited by repetition rate / signal-to-noise requirements
    • Example: 1 ms acquisition has minimum 7 ms duty cycle for up to 3.4 s with good noise floor
    • Duty cycle can be specified
    • Measurement can continue indefinitely at reduced duty cycle (256 ms for above 1 ms example)
  • Start of measurement can be triggered

Triggered Static

Same as Static Measurement, except each measurement is controlled externally.

  • Single trigger to collect single measurement
  • Duty cycle and repetition rate are determined by external trigger

Triggered Time-Resolved

Best time resolution, similar to FT-IR step-scan measurement.

  • Background is collected as pre-trigger samples for each repetition
  • Requires a sample system with a reproducible trigger (like step-scan)
  • Finite time window
  • Sample measurement repeated to build S/N (co-addition)
  • Default time resolution is 4 µs, minimum is 1 µs

More Information

The IRsweep website has an introduction to the dual-comb laser technique and advantages:


Center Wavenumber 1650 cm⁻¹
Bandwidth 50 cm⁻¹
Spectral Sampling 0.3 cm⁻¹
Linewidth <10 MHz (0.0003 cm⁻¹)
Time Resolution <1 μs


Time-resolved spectroscopy with various sample geometries:

  • Transmission
  • Reflection
  • ATR