DFB-RW Laser for Measuring of Water Vapor under Atmospheric Conditions

Functional principle

The laser beam of a tunable DFB-RW laser with a small spectral line width is directed into an integrating sphere. The actual distance of the diffuse scattered light between the entrance of a 4 inch integrating sphere and the photodiode is 7 m.

Optical setup for measuring water vapor
Optical setup for measuring water vapor

This simple setup needs no multi-reflection cells and provides detection limits for water vapor in natural concentrations. Even single rotation-vibration lines can be spectrally resolved.


  • Quantitative measurement of gas concentrations of various molecules, e.g. H2O at 940 nm, O2 at 760 nm, etc.
  • Highly resolved spectroscopic molecular analysis


  • 940 nm

Technology and Mounting

  • Semiconductor structures with MOVPE
  • Laser structures with internal grating


  • Laser technology
  • Highly resolved molecular spectroscopy
  • Gas detection

Typical data

  • Optical output power up to 0.5 W at 940 nm
  • Tuning range up to 7 nm
  • Temperature tuning 0,8 cm-1/K
  • Side-mode suppression ratio better 40 dB
  • Spectral line width smaller 2 MHz
  • Suitable for sub Doppler spectroscopy