Dynamic mode matching of internal and external cavities for enhancing the mode-hop-free synchronous tuning characteristics of an external-cavity diode laser

This paper proposed an external-cavity diode laser (ECDL) that has low-frequency tuning (< 10 Hz) ability using the synchronous tuning principle. However, during high-frequency tuning, the mechanical vibration of the external-cavity system inherent in the ECDL is excited, which will break the mode matching of the internal and external cavities and greatly decrease the mode-hop-free (MHF) tuning range of the ECDL. To obtain a wide MHF range at high-frequency tuning, we used an active internal-cavity mode control method with an inductance–resistance–capacitance (LRC) filter to implement the dynamic mode matching of the internal and external cavities. After using the LRC filter, the experimental results indicated that the MHF tuning range at high-frequency tuning was significantly improved and a maximum wavelength tuning rate of 6.21 THz/s was obtained at tuning frequency of 30 Hz using an uncoated laser diode with a central wavelength of 785 nm.