Abstract

High-frequency characterization of diode lasers is an important topic in studies of high-speed modulation, mode locking, Q-switching, mode selection and tuning, etc. Beating between longitudinal modes in typical diode lasers occurs at frequencies too high to be measured directly. Consequently, mode beating was initially investigated in external-cavity diode lasers, with mode spacings of ~100 MHz.¹ More recently, beating of adjacent longitudinal modes was observed in lasers with 2-2.5-mm long cavities.^2,3 Here, we study mode beating spectra in lasers with cavity length of ~5 mm. For the first time, we have observed beating between second-neighbor modes separated by double spacing.

© 2003 Optical Society of America