THz waves are today used for Imaging (security) and Spectroscopy. The IPR in France recently demonstrated a new dual-frequency 780 nm Ti:Sa laser optimized for high spectral purity tunable CW-THz generation. Optimization of the dual –frequency laser has been based on real time and high-resolution instrument. For dual-frequency laser, more than one laser peak need to be controlled. If a high resolution laser spectrum analyzer is used, one can control the spacing between the two peaks and their absolute wavelength….