Mode-hopping suppression of external cavity diode laser by mode matching

Abstract

Mode hopping is a critical performance limitation of external cavity diode lasers (ECDLs). We developed a method to suppress the mode hops by shifting the internal cavity longitudinal mode spectrum to match the other mode spectra. A model of longitudinal mode structure based on Littman-Metcalf configuration has been deduced for analyzing the characteristics of external cavity mode hop and internal cavity mode hop. The best mode matching point appears at the peak of output power when tuning the ECDL. Both the short-term and long-term wavelength stability were investigated in different laser diode current values while the tuning element maintains a fixed position. The experimental results demonstrated the effectiveness of the proposed mode matching methods for improving the mode stability and reducing the sensitivity to environment change.