Highly Sensitive Spectrometer with 0.78 µm AlGaAs Diode Lasers

Abstract
A reasonably high sensitivity of 3×10-8/cm has been achieved in the near IR spectrometer with AlGaAs diode lasers. Source modulation and Stark modulation techniques are helpful to improve the sensitivity. A successful application to the observation of very weak transitions to the highly excited vibrational states (υN-H=4) of NH3 is demonstrated. All Stark components are resolved and the rotation-vibration transitions are definitely assigned.