Add to ORKGMulti-wavelength laser sources based on Arrayed waveguide grating have been shown in order to provide simultaneously multiples wavelengths with a narrow optical linewidth. Two different laser structures have been developed for the millimeter wave signal generation, monolithically integrated using photonic integrated circuits. In this work we report the characteristics of the heterodyne signal in the millimeter wave range. The optical linewidth measured from the modes generated by different channels on each structure can become less than 150 KHz. Beating the two wavelengths from any of these chips on a high speed photodiode resulted in a beat note having a linewidth less than 250 kHz, which is the narrowest beat-note measured from free runni...